ORCID Profile
0000-0002-8549-4665
Current Organisation
Western Sydney University
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Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Transport Properties and Non-Equilibrium Processes | Organic Chemistry | Nanotechnology | Environmental Science and Management | Physical Chemistry (Incl. Structural) | Composite Materials | Medical Physics | Chemical Engineering | Physical Organic Chemistry | Structural Chemistry and Spectroscopy | Geochronology And Isotope Geochemistry | Environmental Management And Rehabilitation | Mineralogy And Crystallography | Structural Biology (incl. Macromolecular Modelling) | Organic Geochemistry Not Elsewhere Classified | Biophysics | Other Physical Sciences | Nanotechnology | Chemical Engineering Design | Materials Engineering | Food Engineering | Materials Engineering Not Elsewhere Classified | Terrestrial Ecology | Fermentation, Biotechnology And Industrial Microbiology | Condensed Matter Imaging
ANZSRC Socio-Economic Objective (SEO)
Biological sciences | Chemical sciences | Expanding Knowledge in the Chemical Sciences | Inorganic industrial chemicals | Other | Land and water management | Processed food products and beverages not elsewhere classified | Scientific instrumentation | Land and water management | Land and water management | Expanding Knowledge in the Physical Sciences | Cancer and Related Disorders | Treatments (e.g. chemicals, antibiotics) |
Related Links
Publications
Some reflections on the effects of finite gradient pulse lengths in PGSE NMR experiments in restricted systems
Publisher: Wiley
Date: 11-2003
DOI: 10.1560/36L1-H74U-N33X-FY4D
Abstract: It is generally difficult to analytically derive models describing the echo attenuation in pulsed gradient spin‐echo (PGSE) experiments for even the simplest porous systems that are commonly studied—especially when the gradient pulse (δ) is of finite length compared to the timescale of the diffusion measurement (Δ). Consequently, various levels of approximation are used to evaluate PGSE experiments. In the present paper, a conceptual view of q ‐space is given and two of the most common approximations, the short gradient pulse (SGP) and Gaussian phase distribution (GPD) approximations, are compared in detail with a recent matrix method, which provides “analytically” exact results giving a visual representation of the limitations of these approximations. The simulations are performed for diffusion between a pair of reflecting planes separated by a distance a. A modification that is sometimes applied to the short gradient pulse approximation in attempting to extend it to finite gradient pulses is also compared. The simulations reveal that, except when the experimental conditions closely match the requirements of the SGP and GPD simulations, the matrix method must be used in order to correctly interpret the data.
Non-Ideal Behaviour and Solution Interactions in Binary DMSO Solutions
Publisher: Wiley
Date: 02-11-2015
Abstract: The structure and dynamics of hydrogen-bonded structures are of significant importance in understanding many binary mixtures. Since self-diffusion is very sensitive to changes in the molecular weight and shape of the diffusing species, hydrogen-bonded associated structures in dimethylsulfoxide-methanol (DMSO-MeOH) and DMSO-ethanol (DMSO-EtOH) mixtures are investigated using nuclear magnetic resonance (NMR) diffusion experiments and molecular dynamics (MD) simulations over the entire composition range at 298 K. The self-diffusion coefficients of DMSO-MeOH and DMSO-EtOH mixtures decrease by up to 15% and 10%, respectively, with DMSO concentration, indicating weaker association as compared to DMSO-water mixtures. The calculated heat of mixing and radial distribution functions reveal that the intermolecular structures of DMSO-MeOH and DMSO-EtOH mixtures do not change on mixing. DMSO-alcohol hydrogen-bonded dimers are the dominant species in mixtures. Direct comparison of the simulated and experimental data afford greater insights into the structural properties of binary mixtures.
Numerical analysis of NMR diffusion measurements in the short gradient pulse limit
Publisher: Elsevier BV
Date: 09-2013
DOI: 10.1016/J.JMR.2013.06.019
Abstract: Pulsed gradient spin-echo (PGSE) NMR diffusion measurements provide a powerful technique for probing porous media. The derivation of analytical mathematical models for analysing such experiments is only straightforward for ideal restricting geometries and rapidly becomes intractable as the geometrical complexity increases. Consequently, in general, numerical methods must be employed. Here, a highly flexible method for calculating the results of PGSE NMR experiments in porous systems in the short gradient pulse limit based on the finite element method is presented. The efficiency and accuracy of the method is verified by comparison with the known solutions to simple pore geometries (parallel planes, a cylindrical pore, and a spherical pore) and also to Monte Carlo simulations. The approach is then applied to modelling the more complicated cases of parallel semipermeable planes and a pore hopping model. Finally, the results of a PGSE measurement on a toroidal pore, a geometry for which there is presently no current analytical solution, are presented. This study shows that this approach has great potential for modelling the results of PGSE experiments on real (3D) porous systems. Importantly, the FEM approach provides far greater accuracy in simulating PGSE diffraction data.
Nanoassemblies of Gd-DTPA-monooleyl and glycerol monooleate amphiphiles as potential MRI contrast agents
Publisher: Royal Society of Chemistry (RSC)
Date: 2014
DOI: 10.1039/C3TB21069C
A Simple and Effective Binomial Block Based Pulse Sequence Capable of Suppressing Multiple NMR Signals
Publisher: American Chemical Society (ACS)
Date: 26-11-2018
Abstract: A binomial-like block based multiple suppression NMR pulse sequence, termed MULTI-GATE-FSB, that is simple to implement with outstanding suppression performance for multiple solvent signals (or multiple resonances) is investigated. The sequence was tested on two water-alcohol solvent systems, and a standard lysozyme s le, with suppression of three or four regions (though it is extendable to any number of regions). The suppression of all solvent signals was possible in the alcohol-water systems tested with both long and short recycle delays and without the requirement for lengthy presaturation pulses. Such a sequence holds promise not only for LC-NMR applications and solvent suppression but for multiple suppression applications in general (e.g., analysis of impurities/components).
Low-bandwidth space/frequency component separation for quantitative imaging
Publisher: Wiley
Date: 03-10-2017
DOI: 10.1002/MRC.4521
Abstract: Quantitative MRI is often used to analyse multicomponent systems. The analysis requires the contributions from different species to be isolated. Species with distinct chemical shifts can be separated by using a low acquisition bandwidth, which is easy to achieve in common quantitative imaging protocols. The bandwidth reduction leads to separation of NMR contributions from different species in the image space. This new method was implemented and tested on two multicomponent systems containing several spectrally and spatially unresolved components with both distinctly different and similar diffusion coefficients and relaxation times. Separation was achieved with routine MRI diffusion and relaxation measurement pulse sequences in a microimaging environment for water olyethylene glycol solution and for chloroform/TMS olyethylene glycol solution. Conventional monoexponential fitting was used to determine diffusion coefficients and relaxation times from the spectrally separated data, whereas biexponential or triexponential fitting was required in the unseparated reference experiments. In the two-component s le, the variation in the determined fast diffusing components was on the same order of magnitude for all experiments, while the variation in the slow diffusing polyethylene glycol was larger when no separation was present. The separation technique provided lower variability for all the determined diffusion coefficients and relaxation times in the three-component s le. The low-bandwidth separation method can provide separation of multicomponent systems based on the chemical shift difference between the species. The accuracy of the technique is comparable with the commonly used methods for bicomponent system analysis and surpasses those when there are more than two components in the s le. Copyright © 2016 John Wiley & Sons, Ltd.
Preparation and physical properties of a macroscopically aligned lyotropic hexagonal phase templated hydrogel
Publisher: Elsevier BV
Date: 07-2013
Comment on “Molecules, the Ultimate Nanomotor: Linking Chemical Reaction Intermediates to their Molecular Diffusivity”
Publisher: American Chemical Society (ACS)
Date: 26-07-2022
MAG-PGSTE: A new STE-based PGSE NMR sequence for the determination of diffusion in magnetically inhomogeneous samples
Publisher: Elsevier BV
Date: 11-2008
DOI: 10.1016/J.JMR.2008.08.002
Abstract: A new stimulated echo based pulsed gradient spin-echo sequence, MAG-PGSTE, has been developed for the determination of self-diffusion in magnetically inhomogeneous s les. The sequence was tested on two glass bead s les (i.e., 212-300 and <106 microm glass bead packs). The MAG-PGSTE sequence was compared to the MAGSTE (or MPFG) (P.Z. Sun, J.G. Seland, D. Cory, Background gradient suppression in pulsed gradient stimulated echo measurements, J. Magn. Reson. 161 (2003) 168-173 P.Z. Sun, S.A. Smith, J. Zhou, Analysis of the magic asymmetric gradient stimulated echo sequence with shaped gradients, J. Magn. Reson. 171 (2004) 324-329 P.Z. Sun, Improved diffusion measurement in heterogeneous systems using the magic asymmetric gradient stimulated echo (MAGSTE) technique, J. Magn. Reson. 187 (2007) 177-183 P. Galvosas, F. Stallmach, J. Kärger, Background gradient suppression in stimulated echo NMR diffusion studies using magic pulsed field gradient ratios, J. Magn. Reson. 166 (2004) 164-173, P. Galvosas, PFG NMR-Diffusionsuntersuchungen mit ultra-hohen gepulsten magnetischen Feldgradienten an mikroporösen Materialien, Ph.D. Thesis, Universität Leipzig, 2003, P.Z. Sun, Nuclear Magnetic Resonance Microscopy and Diffusion, Ph.D. Thesis, Massachusetts Institute of Technology, 2003] sequence and Cotts 13-interval [R.M. Cotts, M.J.R. Hoch, T. Sun, J.T. Marker, Pulsed field gradient stimulated echo methods for improved NMR diffusion measurements in heterogeneous systems, J. Magn. Reson. 83 (1989) 252-266] sequence using both glass bead s les. The MAG-PGSTE and MAGSTE (or MPFG) sequences outperformed the Cotts 13-interval sequence in the measurement of diffusion coefficients more interestingly, for the s le with higher background gradients (i.e., the <106 microm glass bead s le), the MAG-PGSTE sequence provided higher signal-to-noise ratios and thus better diffusion measurements than the MAGSTE and Cotts 13-interval sequences. In addition, the MAG-PGSTE sequence provided good characterization of the surface-to-volume ratio for the glass bead s les.
Controlled Diffusion of Photoswitchable Receptors by Binding Anti-electrostatic Hydrogen-Bonded Phosphate Oligomers
Publisher: American Chemical Society (ACS)
Date: 12-11-2020
DOI: 10.1021/JACS.0C09072
Use of diffusion magnetic resonance imaging to correlate the developmental changes in grape berry tissue structure with water diffusion patterns
Publisher: Springer Science and Business Media LLC
Date: 04-11-2014
Corrigendum to: Time-Resolved Diffusion NMR Measurements for Transient Processes (ChemPhysChem, (2019), 20, 7, (926-930), 10.1002/cphc.201900150)
Publisher: Wiley
Date: 26-03-2019
NMR diffusion studies of spherical molecules: Tetramethylsilane and buckyballs
Publisher: Elsevier BV
Date: 02-2016
Enhanced Diffusion of Molecular Catalysts Is Due to Convection
Publisher: American Chemical Society (ACS)
Date: 14-06-2019
DOI: 10.26434/CHEMRXIV.8259317
Abstract: Intriguing reports of enhanced diffusion in enzymes and molecular catalysts have spurred significant interest in experimental and theoretical investigations of this phenomenon, with mechanistic understanding the subject of ongoing and lively debate. Here we use time-resolved diffusion NMR methods to measure the diffusion coefficients of small molecule species involved in chemical reactions with high temporal resolution. We show the enhanced diffusion of small molecules cannot be explained by reaction velocity, and that apparent measurements of enhanced diffusion by small molecules appear to be caused by bulk fluid flow processes such as convection. br
Common problems and artifacts encountered in solution-state NMR experiments
Publisher: Wiley
Date: 03-2016
DOI: 10.1002/CMR.A.21387
Hypophosphite transport in human erythrocytes studied by overdetermined one‐dimensional NMR exchange analysis
Publisher: Wiley
Date: 04-1990
Abstract: The membrane transport kinetics of the disubstituted phosphorus oxyacid, hypophosphite, were studied in human red cells under equilibrium exchange conditions. Hypophosphite is an analogue of both the bicarbonate and phosphate ions and is known to be rapidly transported across the human red cell membrane via the anion transport protein, Band 3. The hypophosphite ion is a particularly useful probe of Band 3-mediated membrane transport as the intracellular and extracellular species occur as distinct resonances in the 31P NMR spectrum as a result the membrane potential may also be readily inferred. We applied 'overdetermined' one-dimensional exchange analysis to estimate the rates of exchange for influx and efflux. The apparent equilibrium exchange (ee) values Kmee for the hypophosphite efflux and influx were different and while the efflux parameters were not able to be unambiguously defined, the measured apparent influx kinetic transport parameters were Vmaxee = 1600 +/- 190 amol cell-1 s-1, and Kmee = 75 +/- 16 mM.
Explicit phenomenological solutions for magnetization exposed to an arbitrary NMR diffusion steady state pulse sequence
Publisher: AIP Publishing
Date: 14-10-2021
DOI: 10.1063/5.0062190
Abstract: Explicit phenomenological solutions to recurrence relations for the bulk transverse and longitudinal magnetization found using the Torrey–Bloch equations with relaxation effects are used to investigate nuclear magnetic resonance (NMR) diffusion measurements. Of particular interest are steady state NMR (self-)diffusion measurements that reduce experimental time that can extend the techniques to quickly reacting systems. The solutions for bulk transverse and longitudinal magnetization presented here are used to investigate the average behavior of the transverse and longitudinal magnetization in forming a steady state and are used to derive new expressions for the steady state longitudinal magnetization. These solutions can be applied to a noninteracting spin 1/2 ensemble undergoing free diffusion exposed to an arbitrary NMR pulse sequence containing arbitrary magnetic field gradient waveforms. The closed algebraic form method presented here has an advantage over iterative procedures for calculating transverse and longitudinal magnetization for the analysis and development of steady state pulse sequences. Previous theoretical results for steady state diffusion measurements are also reproduced. The Mathematica code for these solutions is provided in the supplementary material.
Characterization of the solution properties of Pichia farinosa killer toxin using PGSE NMR diffusion measurements.
Publisher: Springer Science and Business Media LLC
Date: 1999
Ionic conduction and ion diffusion in binary room-temperature ionic liquids composed of [emim][BF4] and LiBF4
Publisher: American Chemical Society (ACS)
Date: 20-11-2004
DOI: 10.1021/JP0476601
Nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) studies of corn at subzero temperatures
Publisher: Elsevier BV
Date: 07-2005
A PGSE diffusion and electrophoretic NMR study of Cs+ and Na+ dynamics in aqueous crown ether systems
Publisher: Wiley
Date: 08-12-2007
DOI: 10.1002/MRC.1936
Abstract: Multinuclear pulsed gradient spin-echo (PGSE) NMR diffusion and linewidth measurements were used to probe binding and transport in aqueous Na+-15-crown-5, Na+-18-crown-6, Cs+-15-crown-5 and Cs+-18-crown-6 systems. Since direct PGSE observation of many alkali cations is precluded by either low inherent sensitivity or rapid relaxation (or both), the feasibility of proton-detected electrophoretic NMR (ENMR) measurements to complement PGSE data was investigated. ENMR measurements were performed on aqueous Cs+-, Li+-, Na+-, K+-, and Rb+- 18-crown-6 systems. The data analysis is based on a two-site binding model and its corresponding association constants. Cs+ was found to bind considerably more tightly to 18-crown-6 (K=8 M-1) than to 15-crown-5 (K approximately 2 M-1), whereas Na+ had almost equal affinity (K approximately 4.5 M-1) for 15-crown-5 and 18-crown-6. The difficulties encountered in analysing the NMR parameters, methodological limitations and the implied need for more complicated binding models are discussed.
Macroscopic background gradient and radiation damping effects on high-field PGSE NMR diffusion measurements
Publisher: Elsevier BV
Date: 05-2001
Correlation of viscosity and conductance with23Na+ NMR T1 measurement
Publisher: The Chemical Society of Japan
Date: 10-1990
DOI: 10.1246/BCSJ.63.2961
Chapter 16. Q-space Singlet NMR
Publisher: Royal Society of Chemistry
Date: 2020
NMR diffusometry
Publisher: Springer International Publishing
Date: 2018
Rapid Online Analysis of Photopolymerization Kinetics and Molecular Weight Using Diffusion NMR
Publisher: American Chemical Society (ACS)
Date: 11-01-2022
DOI: 10.1021/ACSMACROLETT.1C00719
Abstract: Online, high-throughput molecular weight analysis of polymerizations is rare, with most studies relying on tedious s ling techniques and batchwise postanalysis. The ability to track both monomer conversion and molecular weight evolution in real time could underpin precision polymer development and facilitate study of rapid polymerization reactions. Here, we use a single time-resolved diffusion nuclear magnetic resonance (NMR) experiment to simultaneously study the kinetics and molecular weight evolution during a photopolymerization, with in situ irradiation inside the NMR instrument. As a model system, we used a photoinduced electron transfer reversible addition-fragmentation chain transfer (PET-RAFT) polymerization. The data allow diffusion coefficients and intensities to be calculated every 14 s from which the polymer size and monomer conversion can be extracted. Key to this approach is (1) the use of shuffled gradient litudes in the diffusion NMR experiment to access reactions of any rate, (2) the addition of a relaxation agent to increase achievable time resolution and, (3) a sliding correction that accounts for viscosity changes during polymerization. Diffusion NMR offers a uniquely simple, translatable handle for online monitoring of polymerization reactions.
Physical characterization using diffusion NMR spectroscopy
Publisher: Wiley
Date: 17-10-2017
DOI: 10.1002/MRC.4530
Abstract: NMR diffusion measurements (or dNMR) provide a powerful tool for analysis of solution organization and microgeometry of the environment by probing random molecular motion. Being a very versatile method, dNMR can be applied to a large variety of s les and systems. Here, a brief introduction into dNMR and a summary of recent advances in the field are presented. The research topics include restricted diffusion, anisotropic diffusion, polymer dynamics, solution structuring and dNMR method development. The dNMR studied systems include plants, cells (cell models), liquid crystals, polymer solutions, ionic liquids, supercooled solutions, untreated water, amino acid solutions and more. It is demonstrated how a variety of dNMR methods can be applied to a system to extract the data on particular structures present among, formed by or surrounding the diffusing particles. It is also demonstrated how dNMR methods can be developed to allow probing larger geometries, low s le concentrations and faster processes. Copyright © 2016 John Wiley & Sons, Ltd.
NMR and ion conductivity studies on cross-linked poly(ethyleneoxide-propyleneoxide) and branched polyether doped with LiN(SO2CF3)2
Publisher: Elsevier BV
Date: 03-2001
The transport and conductivity properties of the ionic liquid EMIMTCM
Publisher: Elsevier BV
Date: 2015
High ice nucleation activity located in blueberry stem bark is linked to primary freeze initiation and adaptive freezing behaviour of the bark
Publisher: Oxford University Press (OUP)
Date: 31-07-2014
Solvent suppression using phase-modulated binomial-like sequences and applications to diffusion measurements
Publisher: Elsevier BV
Date: 09-2008
DOI: 10.1016/J.JMR.2008.06.004
Abstract: Two phase-modulated binomial-like pi pulses have been developed by simultaneously optimizing pulse durations and phases. In combination with excitation sculpting, both of the new binomial-like sequences outperform the well-known 3-9-19 sequence in selectivity and inversion width. The new sequences provide similar selectivity and inversion width to the W5 sequence but with significantly shorter sequence durations. When used in PGSTE-WATERGATE, they afford highly selective solvent suppression in diffusion experiments.
Enhanced Diffusion of Molecular Catalysts is Due to Convection
Publisher: Wiley
Date: 12-11-2019
Abstract: Intriguing reports of enhanced diffusion in enzymes and molecular catalysts have spurred significant interest in experimental and theoretical investigations, and the mechanism of this phenomenon is the topic of lively debate. Here we use time‐resolved diffusion NMR methods to measure the diffusion coefficients ( D ) of small molecule species involved in chemical reactions with high temporal resolution. We show the enhanced diffusion of small molecules cannot be explained by reaction velocity, and that apparent measurements of enhanced diffusion by small molecules appear to be caused by bulk fluid flow processes such as convection.
Comment on “Boosted molecular mobility during common chemical reactions”
Publisher: American Association for the Advancement of Science (AAAS)
Date: 15-01-2021
Abstract: The apparent “boosted mobility” observed by Wang et al . (Reports, 31 July 2020, p. 537) is the result of a known artifact. When signal intensities are changing during a nuclear magnetic resonance (NMR) diffusion measurement for reasons other than diffusion, the use of monotonically increasing gradient litudes produces erroneous diffusion coefficients. We show that no boosted molecular mobility is observed when shuffled gradient litudes are applied.
Steady state effects in PGSE NMR diffusion experiments
Publisher: Elsevier BV
Date: 09-2008
PGSE-WATERGATE, a new tool for NMR diffusion-based studies of ligand-macromolecule binding
Publisher: Wiley
Date: 2002
DOI: 10.1002/MRC.1029
Hydrogen isotope replacement changes hydration and large scale structure, but not small scale structure, of agarose hydrogel networks
Publisher: Springer Science and Business Media LLC
Date: 05-2019
DOI: 10.1140/EPJE/I2019-11816-9
Abstract: Agarose s les of low (Ag1) and high (Ag2) O -methyl content on position 6 of the galactose residue were studied in H
Averaging Effects in PGSE NMR Attenuations Observed in Bimodal Molecular Weight PMMA Solutions
Publisher: American Chemical Society (ACS)
Date: 12-08-2010
DOI: 10.1021/MA1017007
Impediments to the accurate structural characterisation of a highly concentrated emulsion studied using NMR diffusion diffraction
Publisher: Elsevier BV
Date: 10-2009
DOI: 10.1016/J.JCIS.2009.06.014
Abstract: Pulsed gradient spin-echo (PGSE) NMR diffusion studies with subsequent analysis using the Gaussian phase distribution (GPD) approach have long been used to determine the structure of emulsions. With the increasing availability of spectrometers equipped with higher gradient strength generation capabilities it is possible to extend PGSE measurements to where diffusive diffraction effects become evident. However the GPD approach cannot predict these diffraction-like coherence features which can be a rich source of information. With appropriate modelling based on the short gradient pulse approximation (SGP) such coherence features can provide morphological characteristics such as pore size, tortuosity, and connectivity. Further, the deviation of coherence features from ideal cases can be used to elucidate additional features such as the polydispersity of emulsion droplets which is a fundamental and crucial physical characteristic that influences the emulsion stability, rheology, and functionality. In this study analysis of PGSE NMR diffusion diffraction coherence features using the multiple propagator matrix formalism extension of the SGP approach is used to study structural characteristics of a highly concentrated emulsion.
Following Molecular Mobility during Chemical Reactions: No Evidence for Active Propulsion
Publisher: American Chemical Society (ACS)
Date: 02-12-2021
DOI: 10.1021/JACS.1C09455
Abstract: The reported changes in self-diffusion of small molecules during reactions have been attributed to "boosted mobility". We demonstrate the critical role of changing concentrations of paramagnetic ions on nuclear magnetic resonance (NMR) signal intensities, which led to erroneous measurements of diffusion coefficients. We present simple methods to overcome this problem. The use of shuffled gradient litudes allows accurate diffusion NMR measurements, even with time-dependent relaxation rates caused by changing concentrations of paramagnetic ions. The addition of a paramagnetic relaxation agent allows accurate determination of both diffusion coefficients and reaction kinetics during a single experiment. We analyze a copper-catalyzed azide-alkyne cycloaddition "click" reaction, for which boosted mobility has been claimed. With our methods, we accurately measure the diffusive behavior of the solvent, starting materials, and product and find no global increase in diffusion coefficients during the reaction. We overcome NMR signal overlap using an alternative reducing agent to improve the accuracy of the diffusion measurements. The alkyne reactant diffuses slower as the reaction proceeds due to binding to the copper catalyst during the catalytic cycle. The formation of this intermediate was confirmed by complementary NMR techniques and density functional theory calculations. Our work calls into question recent claims that molecules actively propel or swim during reactions and establishes that time-resolved diffusion NMR measurements can provide valuable insight into reaction mechanisms.
Influence of polymer architecture on the averaging effects in PGSE NMR attenuations for bimodal solutions of linear and star poly(vinyl acetates)
Publisher: Elsevier BV
Date: 03-2012
Comment on “Using NMR to Test Molecular Mobility during a Chemical Reaction”
Publisher: American Chemical Society (ACS)
Date: 24-06-2021
Freezing behaviours in wintering Cornus florida flower bud tissues revisited using MRI
Publisher: Wiley
Date: 13-10-2016
DOI: 10.1111/PCE.12813
Abstract: How plant tissues control their water behaviours (phase and movement) under subfreezing temperatures through adaptative strategies (freezing behaviours) is important for their survival. However, the fine details of freezing behaviours in complex organs and their regulation mechanisms are poorly understood, and non-invasive visualization/analysis is required. The localization/density of unfrozen water in wintering Cornus florida flower buds at subfreezing temperatures was visualized with high-resolution magnetic resonance imaging (MRI). This allowed tissue-specific freezing behaviours to be determined. MRI images revealed that in idual anthers and ovules remained stably supercooled to -14 to -21 °C or lower. The signal from other floral tissues decreased during cooling to -7 °C, which likely indicates their extracellular freezing. Microscopic observation and differential thermal analyses revealed that the abrupt breakdown of supercooled in idual ovules and anthers resulted in their all-or-nothing type of injuries. The distribution of ice nucleation activity in flower buds determined using a test tube-based assay corroborated which tissues primarily froze. MRI is a powerful tool for non-invasively visualizing unfrozen tissues. Freezing events and/or dehydration events can be located by digital comparison of MRI images acquired at different temperatures. Only anthers and ovules preferentially remaining unfrozen are a novel freezing behaviour in flower buds. Physicochemical and biological mechanisms/implications are discussed.
Diffusion-diffraction using singlet spin states and various NMR coherences in a J-coupled AX spin system
Publisher: Royal Society of Chemistry (RSC)
Date: 2012
DOI: 10.1039/C2RA20063E
Thiol-water proton exchange of glutathione, cysteine, and N-acetylcysteine: Implications for CEST MRI
Publisher: Wiley
Date: 06-09-2022
DOI: 10.1002/NBM.4188
Abstract: Amide-, amine-, and hydroxyl-water proton exchange can generate MRI contrast through chemical exchange saturation transfer (CEST). In this study, we show that thiol-water proton exchange can also generate quantifiable CEST effects under near-physiological conditions (pH = 7.2 and 37°C) through the characterization of the pH dependence of thiol proton exchange in phosphate-buffered solutions of glutathione, cysteine, and N-acetylcysteine. The spontaneous, base-catalyzed, and buffer-catalyzed exchange contributions to the thiol exchange were analyzed. The thiol-water proton exchange of glutathione and cysteine was found to be too fast to generate a CEST effect around neutral pH due to significant base catalysis. The thiol-water proton exchange of N-acetylcysteine was found to be much slower, yet still in the fast-exchange regime with significant base and buffer catalysis, resulting in a 9.5% attenuation of the water signal at pH 7.2 in a slice-selective CEST NMR experiment. Furthermore, the N-acetylcysteine thiol CEST was also detectable in human serum albumin and agarose phantoms.
Selected applications of NMR spectroscopy
Publisher: CRC Press
Date: 13-10-2014
DOI: 10.1201/B17535
Viscous Calibration Liquids for Self-Diffusion Measurements
Publisher: American Chemical Society (ACS)
Date: 06-08-2015
Quantification of placental change in mouse models of preeclampsia using magnetic resonance microscopy
Publisher: PAGEPress Publications
Date: 03-04-2018
Abstract: Abnormal development of the placenta is postulated to be central to the aetiology of preecl sia. This study investigates changes in placental histopathology in mouse models of preecl sia compared to the morphology using magnetic resonance microscopy (MRM) (11.7 T) of intact ex vivo tissue followed by 3D analysis of the image data. Here, C57BL/6JArc pregnant mice were subject to either normal pregnancy (n=3), or to one of two experimental models of preecl sia TNF-α infusion (n=3) or reduced uterine perfusion pressure(RUPP) (n=3). Placental tissue was collected at gestational day (gd) 17, fixed in formalin and incubated with Magnavist™ contrast agent, and high resolution images (50 μm × 50 μm × 50 μm voxels) obtained by magnetic resonance imaging at 11.74 T. Visual segmentation into placental subregions and three dimensional (3D) reconstruction followed by volume analysis was performed with Amira™ 3D analysis software. The significance of differences between treatment groups in total and regional volumes was assessed. In a single placenta the volumes measure by standard histology were compared. Three placentas from each animal were imaged, segmented into anatomical regions and 3D reconstructions generated. Total placental volume, labyrinth and decidual volume were not significantly different between groups. The junctional zone volume was found to be significantly larger in the RUPP animals (18.5±1.5 mm3) compared to TNF-α infused animals (15.8±1.5) or control animals (15.0±0.7, P .01). However, the decidual/junctional zone volume was smaller in the TNF-a compared to control animals (P .05). Placental structural change in experimental models of preecl sia is able to be visualized and quantified using MRM and 3-D analysis. These techniques could prove to be a powerful tool in examining changes in placental morphology.
MQ-PGSTE: A new multi-quantum STE-based PGSE NMR sequence
Publisher: Elsevier BV
Date: 06-2009
Enhanced Diffusion of Molecular Catalysts Is Due to Convection
Publisher: American Chemical Society (ACS)
Date: 14-06-2019
DOI: 10.26434/CHEMRXIV.8259317.V2
Abstract: Intriguing reports of enhanced diffusion in enzymes and molecular catalysts have spurred significant interest in experimental and theoretical investigations of this phenomenon, with mechanistic understanding the subject of ongoing and lively debate. Here we use time-resolved diffusion NMR methods to measure the diffusion coefficients of small molecule species involved in chemical reactions with high temporal resolution. We show the enhanced diffusion of small molecules cannot be explained by reaction velocity, and that apparent measurements of enhanced diffusion by small molecules appear to be caused by bulk fluid flow processes such as convection.
WaterControl: self-diffusion based solvent signal suppression enhanced by selective inversion
Publisher: Wiley
Date: 28-02-2017
DOI: 10.1002/MRC.4420
Abstract: Selective inversion/excitation based solvent signal suppression techniques are widely used in various NMR experiments because of their high efficiency and general applicability. However, these techniques generate a 'null'/suppression region containing (non-quantitatively) degraded solvent and desired resonances because of their reliance on the rejection of the coherence transfer pathway corresponding to all the resonances within the suppression region. To address this issue, the WaterControl technique was developed by inserting a (pulsed gradient - selective inversion pulse - pulsed gradient) unit into each 'transverse' period of a standard stimulated echo pulse sequence so that the coherence transfer pathways corresponding to both the suppression and non-suppression regions can be selected in one transient. The new sequence affords a diffusion based and quantifiable solvent signal suppression with no or minimal loss of features of interest. Copyright © 2016 John Wiley & Sons, Ltd.
NMR studies of translational motion
Publisher: Cambridge University Press
Date: 30-07-2009
Abstract: Translational motion in solution, either diffusion or fluid flow, is at the heart of chemical and biochemical reactivity. Nuclear Magnetic Resonance (NMR) provides a powerful non-invasive technique for studying the phenomena using magnetic field gradient methods. Describing the physical basis of measurement techniques, with particular emphasis on diffusion, balancing theory with experimental observations and assuming little mathematical knowledge, this is a strong, yet accessible, introduction to the field. A detailed discussion of magnetic field gradient methods applied to Magnetic Resonance Imaging (MRI) is included, alongside extensive referencing throughout, providing a timely, definitive book to the subject, ideal for researchers in the fields of physics, chemistry and biology.
Back Cover: Non‐Ideal Behaviour and Solution Interactions in Binary DMSO Solutions (ChemPhysChem 18/2015)
Publisher: Wiley
Date: 12-2015
Characterisation of internal oxygen concentration of strawberry (
Publisher: CSIRO Publishing
Date: 16-12-2022
DOI: 10.1071/FP21259
Abstract: Gas exchange mechanisms play crucial roles in maintaining fruit post-harvest quality in perishable fruit such as strawberry (Fragaria × ananassa Duch.) and blueberry (Vaccinium corymbosum L.). The internal oxygen concentration ([O2]) of strawberry and blueberry were measured using Clark-type oxygen sensing electrodes. The volume of intercellular voids in strawberry was obtained by micro-computed tomography (micro-CT). In both berries, internal [O2] was consistent and relatively high across measured tissues. The overall [O2] was well above the Michaelis constant (Km) for cytochrome c oxidase in both fruit and different from previously examined grape (Vitis vinifera L.) berry mesocarp with near zero minimum [O2]. In strawberry and blueberry, cell vitality was also maintained at full maturity in the mesocarp. Higher storage temperature (i.e. 20 vs 4°C) reduced internal [O2] of strawberry. Pedicel detachment in blueberry was associated with greater fruit dehydration and lower internal [O2] after short-term storage of 12 h. The results suggest that the intercellular voids of the fruit’s mesocarp provide an efficient gas exchange route for maintaining high fruit internal [O2] post-harvest.
Diffusion NMR: A Tool to Investigate the Dynamics of Organic Systems
Publisher: Bentham Science Publishers Ltd.
Date: 23-05-2018
Steady state effects in a two-pulse diffusion-weighted sequence
Publisher: AIP Publishing
Date: 20-04-2015
DOI: 10.1063/1.4918279
Abstract: In conventional nuclear magnetic resonance (NMR) diffusion measurements a significant amount of experimental time is used up by magnetization recovery, serving to prevent the formation of the steady state, as in the latter case the manifestation of diffusion is modulated by multiple applications of the pulse sequence and conventional diffusion coefficient inference procedures are generally not applicable. Here, an analytical expression for diffusion-related effects in a two-pulse NMR experiment (e.g., pulsed-gradient spin echo) in the steady state mode (with repetition times less than the longitudinal relaxation time of the s le) is derived by employing a Fourier series expansion within the solution of the Bloch-Torrey equations. Considerations are given for the transition conditions between the full relaxation and the steady state experiment description. The diffusion coefficient of a polymer solution (polyethylene glycol) is measured by a two-pulse sequence in the full relaxation mode and for a range of repetition times, approaching the rapid steady state experiment. The precision of the fitting employing the presented steady state solution by far exceeds that of the conventional fitting. Additionally, numerical simulations are performed yielding results strongly supporting the proposed description of the NMR diffusion measurements in the steady state.
Diffusion NMR studies on fish antifreeze proteins and synthetic analogues
Publisher: Wiley
Date: 19-06-2006
DOI: 10.1016/J.FEBSLET.2006.06.022
Abstract: Pulsed field gradient spin echo NMR spectroscopy was used to measure diffusion coefficients of the alpha-helical type I antifreeze protein from the winter flounder, two synthetic derivatives in which the four Thr residues were replaced with Val and Ala, respectively, and the low molecular weight fraction antifreeze glycoprotein. Under the conditions studied, the natural type I antifreeze protein and low molecular weight glycoprotein gave diffusion values that were consistent with the presence of monomeric protein in solution. While significant aggregation of the Ala analogue was observed (2-10 mM), there was no evidence for aggregation in the Val analogue (1-3 mM). These results are compared with previously reported solubility and thermal hysteresis data and the implications for the design of synthetic antifreeze proteins are discussed.
Inside Back Cover: NMR Diffusion Measurements as a Simple Method to Examine Solvent–Solvent and Solvent–Solute Interactions in Mixtures of the Ionic Liquid [Bmim][N(SO2CF3)2
Publisher: Wiley
Date: 05-12-2016
Simultaneous convection compensation and solvent suppression in biomolecular NMR diffusion experiments
Publisher: Springer Science and Business Media LLC
Date: 21-08-2009
DOI: 10.1007/S10858-009-9367-2
Abstract: Thermal convection and high intensity solvent resonances can significantly h er diffusion estimates in pulsed gradient spin-echo nuclear magnetic resonance diffusion experiments on biomolecule s les. To overcome these two problems, a new double functional NMR diffusion sequence, double echo PGSTE-WATERGATE, is presented. The new sequence provides excellent convection compensation and solvent suppression (with a suppression factor in excess of at least 10(5) in a single scan) in biomolecular NMR diffusion experiments. Due to its stimulated echo nature, the new sequence is much less susceptible to spin-spin relaxation than Hahn spin-echo based sequences. Furthermore, the new sequence is not susceptible to spin diffusion due to the application of bipolar pulsed gradients. The new sequence is also much easier to set up compared to previously developed stimulated echo based convection compensation and solvent suppression sequence. The utility of the new sequence is demonstrated on an aqueous lysozyme s le.
Chloride‐37 nuclear magnetic resonance spectroscopic study of binding of salicylic acid and other hydroxybenzoic acids to the band 3 anion transport protein of human erythrocytes
Publisher: Elsevier BV
Date: 05-1992
Abstract: Chloride-37 nuclear magnetic resonance spectroscopy was used to investigate the displacement of chloride (Cl-) from binding sites on band 3 anion transport protein in human erythrocytes by salicylic acid and five other hydroxybenzoic acids (HAs). All the HAs studied displaced Cl- from these binding sites. The association constants for binding of the HAs to band 3 anion transport protein were larger than that for Cl- and dependent on the specific structural features of the molecule, rather than general physicochemical characteristics.
Biexponential diffusion decay in formalin-fixed prostate tissue: Preliminary findings
Publisher: Wiley
Date: 09-12-2012
DOI: 10.1002/MRM.23291
Abstract: Magnetic resonance microimaging was used to measure diffusion decay over an extended b-factor range in a formalin-fixed normal prostate s le and a Gleason pattern 3+4 cancer tissue s le. The coefficients of biexponential fits to diffusion decay data from 1600 voxels of dimension 160 × 160 × 160 μm(3) in each s le were correlated with underlying epithelial and stromal compartment partial volumes estimated from high-resolution apparent diffusion coefficient (ADC) data (40 × 40 × 40 μm(3) voxels) from the same tissue. In the normal tissue s le, the signal fractions of the low and high ADC components of the biexponential fits correlated linearly with partial volumes of epithelial tissue (R(2) = 0.6) and stromal tissue (R(2) = 0.5), respectively. Similar but weaker correlations were observed in the cancer s le. Epithelium-containing high spatial resolution voxels appeared to be composed of ∼60% low ADC and ∼40% high ADC component. Stromal voxels appeared to be composed of ∼20% low ADC and ∼80% high ADC component. This preliminary report suggests that distinctly different diffusion properties in microscopically adjacent cell types contribute to the multiexponential diffusion decay phenomenon in prostate tissue.
PGSTE-WATERGATE: An STE-based PGSE NMR sequence with excellent solvent suppression
Publisher: Elsevier BV
Date: 03-2008
DOI: 10.1016/J.JMR.2007.12.001
Abstract: A new stimulated-echo based pulsed gradient spin-echo NMR diffusion sequence incorporating WATERGATE solvent suppression, PGSTE-WATERGATE, is presented. The sequence provides superb solvent suppression without any phase distortions. The sequence is simple to set up and particularly suited to measuring diffusion coefficients in aqueous solution such as is commonly required in pharmaceutical and combinatorial applications. The utility of the sequence is demonstrated on s les containing lysozyme and sucrose. Importantly, the high degree of phase-distortion suppression allows more complicated selective pi pulses to be used to enhance the selectivity of solvent suppression.
1H NMR Diffusion Studies of Water Self-Diffusion in Supercooled Aqueous Sodium Chloride Solutions
Publisher: American Chemical Society (ACS)
Date: 23-04-2014
DOI: 10.1021/JP501472S
Abstract: The physical properties of aqueous sodium chloride solutions have been studied theoretically, but so far no experimental diffusion data have been obtained under supercooled conditions. Here the results of (1)H NMR translational diffusion measurements of water in sodium chloride solutions in the temperature range 230 to 300 K and sodium chloride concentrations up to 4.2 mol/kg are presented. It was found that the diffusion data were well-described by the Vogel-Tamman-Fulcher relationship with concentration-dependent parameters D0, B, and T0. The results indicate that under supercooled conditions the influence of sodium chloride on water diffusion is much smaller than predicted by molecular dynamics simulations.
Enhanced Diffusion of Molecular Catalysts Is Due to Convection
Publisher: American Chemical Society (ACS)
Date: 13-06-2019
DOI: 10.26434/CHEMRXIV.8259317.V1
Abstract: Intriguing reports of enhanced diffusion in enzymes and molecular catalysts have spurred significant interest in experimental and theoretical investigations of this phenomenon, with mechanistic understanding the subject of ongoing and lively debate. Here we use time-resolved diffusion NMR methods to measure the diffusion coefficients of small molecule species involved in chemical reactions with high temporal resolution. We show the enhanced diffusion of small molecules cannot be explained by reaction velocity, and that apparent measurements of enhanced diffusion by small molecules appear to be caused by bulk fluid flow processes such as convection.
NMR studies on poly(ethylene oxide)-based polymer electrolytes with different cross-linking doped with LiN(SO2CF3)2. Restricted diffusion of the polymer and lithium ion and time-dependent diffusion of the anion
Publisher: American Chemical Society (ACS)
Date: 19-03-2003
DOI: 10.1021/MA021741I
A new type of sample tube for reducing convection effects in PGSE-NMR measurements of self-diffusion coefficients of liquid samples
Publisher: Elsevier BV
Date: 04-2004
Self-diffusion coefficients of heavy water in low n-alkanes
Publisher: Elsevier BV
Date: 10-2023
A physical interpretation of product operator terms
Publisher: Wiley
Date: 11-2009
DOI: 10.1002/CMR.A.20151
Comment on “Boosted Molecular Mobility During Common Chemical Reactions
Publisher: American Chemical Society (ACS)
Date: 05-10-2020
DOI: 10.26434/CHEMRXIV.13023164
Abstract: The apparent “boosted mobility” observed by nuclear magnetic resonance (NMR) diffusion measurements is the result of a known artefact. When signal intensities are changing during an NMR diffusion measurement for reasons other than diffusion, the use of monotonically increasing gradient litudes produces erroneous diffusion coefficient values. We show that no boosted molecular mobility is observed when shuffled gradient litudes are applied.
Ion transport properties of six lithium salts dissolved in γ-butyrolactone studied by self-diffusion and ionic conductivity measurements
Publisher: The Electrochemical Society
Date: 2004
DOI: 10.1149/1.1630592
NMR Diffusion Measurements as a Simple Method to Examine Solvent–Solvent and Solvent–Solute Interactions in Mixtures of the Ionic Liquid [Bmim][N(SO2CF3)2] and Acetoni
Publisher: Wiley
Date: 26-10-2016
Abstract: The self-diffusion coefficients of each component in mixtures of 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([Bmim][N(SO
The protective effect of apolipoprotein in models of trophoblast invasion and preeclampsia
Publisher: American Physiological Society
Date: 2017
DOI: 10.1152/AJPREGU.00331.2016
Abstract: Preecl sia is a hypertensive disorder of pregnancy. It is associated with abnormal placentation via poor placental invasion of the uterine vasculature by trophoblast cells, leading to poor placental perfusion, oxidative stress, and inflammation, all of which are implicated in its pathogenesis. A dyslipidemia characterized by low plasma levels of high-density lipoproteins (HDL) and elevated triglycerides has been described in preecl sia. Apolipoprotein A-I (apoA-I), a constituent of HDL is an anti-inflammatory agent. This study investigated whether apoA-I protects against hypertension and adverse placental changes in a proinflammatory cytokine (TNF-α)-induced model of preecl sia. Further, this study investigated whether apoA-I protects against the inhibitory effect of TNF-α in a human in vitro model of trophoblast invasion. Administration of apoA-I to pregnant mice before infusion with TNF-α resulted in a significant reduction in the cytokine-induced increase in systolic blood pressure. MRI measurement of T 2 relaxation, a parameter that is tissue specific and sensitive to physiological changes within tissues, showed a reversal of TNF-α-induced placental changes. Preincubation of endothelial cells with apoA-I protected against the TNF-α-induced inhibition of HTR-8/SVneo (trophoblast) cell integration into endothelial (UtMVEC) networks. These data suggest that a healthy lipid profile may affect pregnancy outcomes by priming endothelial cells in preparation for trophoblast invasion.
Applications of WaterControl to TOCSY and COSY experiments
Publisher: Springer Science and Business Media LLC
Date: 15-05-2020
Gd-DTPA-Dopamine-Bisphytanyl Amphiphile: Synthesis, Characterisation and Relaxation Parameters of the Nanoassemblies and Their Potential as MRI Contrast Agents
Publisher: Wiley
Date: 13-08-2015
Abstract: Here, a new hiphilic magnetic resonance imaging (MRI) contrast agent, a Gd(III)-chelated diethylenetriaminepentaacetic acid conjugated to two branched alkyl chains via a dopamine spacer, Gd-DTPA-dopamine-bisphytanyl (Gd-DTPA-Dop-Phy), which is readily capable of self-assembling into liposomal nanoassemblies upon dispersion in an aqueous solution, is reported. In vitro relaxivities of the dispersions were found to be much higher than Magnevist, a commercially available contrast agent, at 0.47 T but comparable at 9.40 T. Analysis of variable temperature (17)O NMR transverse relaxation measurements revealed the water exchange of the nanoassemblies to be faster than that previously reported for paramagnetic liposomes. Molecular reorientation dynamics were probed by (1)H NMRD profiles using a classical inner and outer sphere relaxation model and a Lipari-Szabo "model-free" approach. High payloads of Gd(III) ions in the liposomal nanoassemblies made solely from the Gd-DTPA-Dop-Phy hiphiles, in combination with slow molecular reorientation and fast water exchange makes this novel hiphile a suitable candidate to be investigated as an advanced MRI contrast agent.
Effects of Higher-Rank Multipoles on Spectral Lineshapes of Higher Quadrupolar Nuclei near the Null Point in Inversion-Recovery Experiments
Publisher: Elsevier BV
Date: 07-1994
NMR Studies of Nanoscale Organization and Dynamics in Polymer Electrolytes
Publisher: CSIRO Publishing
Date: 2004
DOI: 10.1071/CH04155
Abstract: Multinuclear (i.e., 7Li, 19F, and 1H) NMR relaxation and pulsed field gradient spin-echo (PGSE) NMR translational diffusion measurements have been used to study the reorientational and translational dynamics of the polymeric, anionic, and cationic species in a polymer electrolyte system composed of high-molecular-weight comb-branched polyethers and their precursor macromonomers of cross-linked random copolymers, with and without LiN(SO2CF3)2 (LiTFSI) doping. The macromonomers are derivatives of glycerol bonded to ethylene oxide-co-propylene oxide (m(EO-PO)) and are viscous liquids with a molecular weight of approximately 8000. The results were consistent with a picture of the lithium ions undergoing local motions near the polymer chains, whereas the anions diffuse through a slowly fluctuating three-dimensional porous polymer matrix. Four years later, the macromonomer electrolyte s les were re-measured to investigate the effects of long-term aging. The NMR data revealed that the electrolyte has undergone significant structural relaxation. The findings shed light on the evolving molecular architectures that influence conductivity and help to explain the non-ideal conductivity behaviour.
Fast determination of the 1H relaxivities of MRI contrast agents
Publisher: Wiley
Date: 20-08-2016
DOI: 10.1002/MRC.4314
A pulsed field gradient NMR study of the aggregation and hydration of parvalbumin
Publisher: Elsevier BV
Date: 04-1997
DOI: 10.1016/S0301-4622(97)00003-3
Abstract: Pulsed field gradient NMR is a convenient alternative to traditional methods for measuring diffusion of biological macromolecules. In the present study, pulsed field gradient NMR was used to study the effects of calcium binding and hydration on carp parvalbumin. Carp parvalbumin is known to undergo large changes in tertiary structure with calcium loading. The diffusion coefficient is a sensitive guide to changes in molecular shape and in the present study the large changes in tertiary structure were clearly reflected in the measured diffusion coefficient upon calcium loading. The (monomeric) calcium-loaded form had a diffusion coefficient of 1.4 x 10(-10) m(2) s(-1) at 298 K, which conforms with the structure being a nearly spherical prolate ellipsoid from X-ray studies. The calcium-free form had a significantly lower diffusion coefficient of 1.1 x 10(-10) m(2) s(-1). The simplest explanation consistent with the change in diffusion coefficient is that the parvalbumin molecules form dimers upon the removal of Ca(2+) at the protein concentration studied (1 mM).
Errors in the Use of NMR to Test Molecular Mobility during a Chemical Reaction
Publisher: American Chemical Society (ACS)
Date: 29-03-2021
DOI: 10.26434/CHEMRXIV.14306771.V1
Abstract: A study reported in The Journal of Physical Chemistry Letters (12 (2021) 2370) of “boosted mobility” measured by diffusion NMR experiments contains significant errors in data analysis and interpretation. We carefully reanalyzed the same data and find no evidence of boosted mobility, and we identify several sources of error.
Solute transport within grape berries inferred from the paramagnetic properties of manganese
Publisher: CSIRO Publishing
Date: 2017
DOI: 10.1071/FP16406
Abstract: Tracer compounds used for studying solute transport should ideally have identical functions and transport properties to the molecules they are designed to mimic. Unfortunately, the xylem-mobile tracer compounds currently used to infer solute transport mechanisms in botanical specimens such as the fruit of the grapevine, Vitis vinifera L., are typically xenobiotic and have difficulty exiting the xylem during berry ripening. Here it is demonstrated that the transport of paramagnetic Mn ions can be indirectly observed within the grape berry, using relaxation magnetic resonance imaging (MRI). Mn ions from a 10 mM Mn chloride solution were taken up into the grape berry via the pedicel and moved through the peripheral vasculature before exiting into surrounding pericarp tissue. Mn did not exit evenly across the berry, implying that the berry xylem influences which sites Mn exits the vasculature ‘downstream’ of the berry pedicel. It was also found that when the cellular membranes of pericarp tissues were disrupted, the distribution of Mn through the pericarp tissue became noticeably more homogenous. This indicates that the cellular membranes of extra-vascular cells affect the spatial distribution of Mn across the berry extra-vascular pericarp tissue upon exiting the grape berry vasculature.
A magnetic gradient induced force in NMR restricted diffusion experiments
Publisher: AIP Publishing
Date: 24-03-2014
DOI: 10.1063/1.4868865
Abstract: We predict that the phase cancellation of a precessing magnetisation field carried by a diffusing species in a bounded geometry under certain nuclear magnetic resonance pulsed magnetic field gradient sequences results in a small force over typically micrometre length scales. Our calculations reveal that the total magnetisation energy in a pore under the influence of a pulsed gradient will be distance-dependent thus resulting in a force acting on the boundary. It is shown that this effect of the magnetisation of diffusing particles will appear as either an attractive or repulsive force depending on the geometry of the pore and magnetic properties of the material. A detailed analysis is performed for the case of a pulsed gradient spin-echo experiment on parallel planes. It is shown that the force decays exponentially in terms of the spin-spin relaxation. The proof is based on classical electrodynamics. An application of this effect to soft matter is suggested.
NMR diffusometry applied to liquids
Publisher: Elsevier BV
Date: 09-2010
Photocatalytic properties of Ta-doped TiO2
Publisher: Springer Science and Business Media LLC
Date: 10-06-2017
Hydrodynamic size and scaling relations for linear and 4 arm star PVAc studied using PGSE NMR
Publisher: Elsevier BV
Date: 09-2013
Erratum: Measuring progress and projecting attainment on the basis of past trends of the health-related Sustainable Development Goals in 188 countries: an analysis from the Global Burden of Disease Study 2016 (The Lancet (2017) 390(10100) (1423–1459) (S014067361732336X) (10.1016/S0140-6736(17)32336-X))
Publisher: Elsevier BV
Date: 10-2017
Structural changes in copper based metal-organic framework catalyst induced by organic solvents
Publisher: Elsevier BV
Date: 07-2020
Artifacts in Experimental and Simulated Solid-State 2H NMR Powder Spectra
Publisher: Elsevier BV
Date: 05-1995
Porous Upconversion Nanostructures as Bimodal Biomedical Imaging Contrast Agents
Publisher: American Chemical Society (ACS)
Date: 08-05-2020
Solvent signal suppression in NMR
Publisher: Elsevier BV
Date: 04-2010
Magnetic Resonance Imaging Detects Placental Hypoxia and Acidosis in Mouse Models of Perturbed Pregnancies
Publisher: Public Library of Science (PLoS)
Date: 26-03-2013
Efficient and precise calculation of the b-matrix elements in diffusion-weighted imaging pulse sequences
Publisher: Elsevier BV
Date: 06-2014
DOI: 10.1016/J.JMR.2014.03.006
Abstract: Precise NMR diffusion measurements require detailed knowledge of the cumulative dephasing effect caused by the numerous gradient pulses present in most NMR pulse sequences. This effect, which ultimately manifests itself as the diffusion-related NMR signal attenuation, is usually described by the b-value or the b-matrix in the case of multidirectional diffusion weighting, the latter being common in diffusion-weighted NMR imaging. Neglecting some of the gradient pulses introduces an error in the calculated diffusion coefficient reaching in some cases 100% of the expected value. Therefore, ensuring the b-matrix calculation includes all the known gradient pulses leads to significant error reduction. Calculation of the b-matrix for simple gradient waveforms is rather straightforward, yet it grows cumbersome when complexly shaped and/or numerous gradient pulses are introduced. Making three broad assumptions about the gradient pulse arrangement in a sequence results in an efficient framework for calculation of b-matrices as well providing some insight into optimal gradient pulse placement. The framework allows accounting for the diffusion-sensitising effect of complexly shaped gradient waveforms with modest computational time and power. This is achieved by using the b-matrix elements of the simple unmodified pulse sequence and minimising the integration of the complexly shaped gradient waveform in the modified sequence. Such re-evaluation of the b-matrix elements retains all the analytical relevance of the straightforward approach, yet at least halves the amount of symbolic integration required. The application of the framework is demonstrated with the evaluation of the expression describing the diffusion-sensitizing effect, caused by different bipolar gradient pulse modules.
Correlation of ultra-high field MRI with histopathology for evaluation of rectal cancer heterogeneity
Publisher: Springer Science and Business Media LLC
Date: 27-06-2019
DOI: 10.1038/S41598-019-45450-2
Abstract: Current clinical MRI techniques in rectal cancer have limited ability to examine cancer stroma. The differentiation of tumour from desmoplasia or fibrous tissue remains a challenge. Standard MRI cannot differentiate stage T1 from T2 (invasion of muscularis propria) tumours. Diffusion tensor imaging (DTI) can probe tissue structure and organisation (anisotropy). The purpose of this study was to examine DTI-MRI derived imaging markers of rectal cancer stromal heterogeneity and tumour extent ex vivo . DTI-MRI at ultra-high magnetic field (11.7 tesla) was used to examine the stromal microstructure of malignant and normal rectal tissue ex vivo , and the findings were correlated with histopathology. Images obtained from DTI-MRI (A0, apparent diffusion coefficient and fractional anisotropy (FA)) were used to probe rectal cancer stromal heterogeneity. FA provided the best discrimination between cancer and desmoplasia, fibrous tissue and muscularis propria. Cancer had relatively isotropic diffusion (mean FA 0.14), whereas desmoplasia (FA 0.31) and fibrous tissue (FA 0.34) had anisotropic diffusion with significantly higher FA than cancer (p 0.001). Tumour was distinguished from muscularis propria (FA 0.61) which was highly anisotropic with higher FA than cancer (p 0.001). This study showed that DTI-MRI can assist in more accurately defining tumour extent in rectal cancer.
Microviscosity of human erythrocytes studied with hypophosphite and 31P-NMR
Publisher: Elsevier BV
Date: 07-1989
DOI: 10.1016/0301-4622(89)80022-5
Abstract: A 31P-NMR method, which complements earlier 13C-NMR procedures for probing the intra-erythrocyte microenvironment, is described. Hypophosphite is an almost unique probe of the erythrocyte microenvironment, since it is rapidly transported into the cell via the band 3 protein, and intra- and extracellular populations give rise to distinct resonances in the 31P-NMR spectrum. Relaxation mechanisms of the 31P nucleus in the hypophosphite ion were shown to be spin-rotation and dipole-dipole. Analysis of longitudinal relaxation rates in human erythrocytes, haemolysates and concentrated glycerol solutions allowed the determination of microviscosity using the Debye equation. Bulk viscosities of lysates and glycerol solutions were measured using Ostwald capillary viscometry. Translational diffusion coefficients were then calculated from the viscosity estimates using the Stokes-Einstein equation. The results with a range of solvent systems showed that 'viscosity' is a relative phenomenon and that bulk (i.e., macro-) viscosity is therefore not necessarily related to the NMR-determined viscosity. The intracellular NMR-determined viscosities from red cells, ranging in volume from 65.5 to 100.1 fl, varied from 2.10 to 2.67 mPa s. This is consistent with the translational diffusion coefficients of the hypophosphite ion altering by only 20%, whereas the values determined from bulk viscosity measurements conducted on lysates of these cells are consistent with a 230% change.
Applications for Transition-Metal Chemistry in Contrast-Enhanced Magnetic Resonance Imaging
Publisher: American Chemical Society (ACS)
Date: 05-05-2020
A complete derivation of the Kärger equations for analyzing NMR diffusion measurements of exchanging systems
Publisher: Wiley
Date: 03-2019
DOI: 10.1002/CMR.A.21468
NMR studies of polydiacetylenes having alkyl chains. Molecular motions of precursor monomers and the polymers of various stages of the solid-state polymerization
Publisher: Elsevier BV
Date: 1998
Water Signal Suppression in NMR Spectroscopy
Publisher: Elsevier
Date: 1999
NOESY-WaterControl: a new NOESY sequence for the observation of under-water protein resonances
Publisher: Springer Science and Business Media LLC
Date: 03-2017
DOI: 10.1007/S10858-017-0100-2
Abstract: Highly selective and efficient water signal suppression is indispensable in biomolecular 2D nuclear Overhauser effect spectroscopy (NOESY) experiments. However, the application of conventional water suppression schemes can cause a significant or complete loss of the biomolecular resonances at and around the water chemical shift (ω
Pulsed-Field-Gradient NMR of Diffusive Transport through a Spherical Interface into an External Medium Containing a Relaxation Agent
Publisher: Elsevier BV
Date: 05-1995
Direct Hydrodynamic Radius Measurement on Dissolved Organic Matter in Natural Waters Using Diffusion NMR
Publisher: American Chemical Society (ACS)
Date: 19-01-2012
DOI: 10.1021/ES202809E
Abstract: Dissolved organic matter from natural waters is a complex mixture of various chemical components, which play vital roles in many environmental processes such as the global carbon cycle and the fate of many key anthropogenic pollutants. Despite its environmental significance, dissolved organic matter in natural form has never been studied using nuclear magnetic resonance based hydrodynamic radius measurements due to its extremely low concentration (e.g., a few mg/L) in natural waters. In this study, NMR-based hydrodynamic radius measurements were performed directly on unconcentrated pond, river, and sea waters. The key chemical components of the dissolved organic matters from different sources were identified as carbohydrates, carboxyl-rich alicyclic molecules, and aliphatic molecules. By using the Stokes-Einstein-Sutherland equation, the average hydrodynamic radii of the three key components were calculated.
Diffusion-based studies on the self-stacking and nanorod formation of platinum(ii) intercalators
Publisher: Royal Society of Chemistry (RSC)
Date: 2009
DOI: 10.1039/B820584A
Abstract: Pulsed gradient spin-echo nuclear magnetic resonance diffusion measurements have been used to show that platinum(II)-based intercalating agents self-stack in solution and form nanorods 0.45-3.9 nm in length (at 25 mM) their lengths are dependent on metal complex concentration, salt concentration and solution temperature.
Determining a ‘diffusion-averaged’ characteristic ratio for aligned lyotropic hexagonal phases using PGSE NMR self-diffusion measurements, random walk simulations and obstruction models
Publisher: Elsevier BV
Date: 06-2017
Conformation of a Heptadecapeptide Comprising the Segment Encephalitogenic in Rhesus Monkey
Publisher: American Chemical Society (ACS)
Date: 12-1988
DOI: 10.1021/BI00425A017
Abstract: The 17-residue peptide FKLGGRDSRSGSPMARR derived from myelin basic protein, containing an epitope encephalitogenic in rhesus monkey, has been studied in aqueous solution by high-resolution one- and two-dimensional carbon and proton nuclear magnetic resonance spectroscopy. The resonances of the spectra from both nuclei were assigned with the aid of two-dimensional correlated spectroscopy, pH and solvent titrations, and one-dimensional spin-decoupling techniques and by comparison of the spectra of the heptadecapeptide with those of a phosphorylated form of the peptide, the pentadecapeptide FKLGGRDSRSGSPMA, and the nonapeptide FKLGGRDSR. Amide proton temperature coefficients, coupling constants, 13C- spin-lattice relaxation times, and nuclear Overhauser effect data suggest the existence of three structured regions comprising residues 3-6, 7-12, and 12-14 in the solution conformations of the encephalitogenic heptadecapeptide.
Evaluation of Gd-DTPA-monophytanyl and phytantriol nanoassemblies as potential MRI contrast agents
Publisher: American Chemical Society (ACS)
Date: 23-01-2015
DOI: 10.1021/LA5044969
Abstract: Supramolecular self-assembling hiphiles have been widely used in drug delivery and diagnostic imaging. In this report, we present the self-assembly of Gd (III) chelated DTPA-monophytanyl (Gd-DTPA-MP) hiphiles incorporated within phytantriol (PT), an inverse bicontinuous cubic phase forming matrix at various compositions. The dispersed colloidal nanoassemblies were evaluated as potential MRI contrast agents at various magnetic field strengths. The homogeneous incorporation of Gd-DTPA-MP in PT was confirmed by polarized optical microscopy (POM) and synchrotron small-angle X-ray scattering (SAXS) of the bulk phases of the mixtures. The liquid crystalline nanostructures, morphology, and the size distribution of the nanoassemblies were studied by SAXS, cryogenic transmission electron microscopy (cryo-TEM), and dynamic light scattering (DLS). The dispersions with up to 2 mol % of Gd-DTPA-MP in PT retained inverse cubosomal nanoassemblies, whereas the rest of the dispersions transformed to liposomal nanoassemblies. In vitro relaxivity studies were performed on all the dispersions at 0.54, 9.40, and 11.74 T and compared to Magnevist, a commercially available contrast agent. All the dispersions showed much higher relaxivities compared to Magnevist at both low and high magnetic field strengths. Image contrast of the nanoassemblies was also found to be much better than Magnevist at the same Gd concentration at 11.74 T. Moreover, the Gd-DTPA-MP/PT dispersions showed improved relaxivities over the pure Gd-DTPA-MP dispersion at high magnetic fields. These stable colloidal nanoassemblies have high potential to be used as combined delivery matrices for diagnostics and therapeutics.
Controlled Diffusion of Photoswitchable Receptors by Binding Antielectrostatic Phosphate Oligomers
Publisher: American Chemical Society (ACS)
Date: 15-05-2020
DOI: 10.26434/CHEMRXIV.12298919.V1
Abstract: Dihydrogen phosphate anions are found to spontaneously associate into anti-electrostatic oligomers via hydrogen bonding interactions at millimolar concentrations in DMSO. Diffusion NMR measurements supported formation of these oligomers, which can be bound by photoswitchable anion receptors to form large bridged assemblies of approximately three times the volume of the unbound receptor. Photoisomerization of the oligomer-bound receptor causes a decrease in diffusion coefficient of up to 16%, corresponding to a 70% increase in effective volume. This new approach to external control of diffusion opens prospects in controlling molecular transport.
Determination of pore space shape and size in porous systems using NMR diffusometry. Beyond the short gradient pulse approximation
Publisher: Elsevier BV
Date: 02-2003
DOI: 10.1016/S1090-7807(02)00134-9
Abstract: The influence of finite length gradient pulses on NMR diffusion experiments on liquids confined to diffuse between two parallel planes is investigated. It is experimentally verified that the pore size decreases when determined using finite gradient pulses if the results are analyzed within the short gradient pulse approximation. The results are analyzed using the matrix formulation. The observed minima in the echo decay profiles are considerably less sharp than theoretical analysis would indicate and we suggest that this is due to the presence of a distribution of pore sizes in the s le. In addition, effects due to the presence of background gradients are discussed. It is argued that effects due to the finite length gradient pulses are relatively minor and in realistic applications the effects due to inhomogeneities in pore sizes and effects due to background gradients will constitute more serious problems in pore size determinations by means of NMR diffusometry.
Time-Resolved Diffusion NMR Measurements for Transient Processes
Publisher: Wiley
Date: 05-03-2019
Abstract: A general procedure for measurement of time-resolved diffusion coefficients of molecular species by NMR is described, including the use of methanol for fast temperature-independent gradient calibration.
Towards advanced paramagnetic nanoassemblies of highly ordered interior nanostructures as potential MRI contrast agents
Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C6NJ03934K
Abstract: A novel paramagnetic hiphile designed to form nanoassemblies of highly ordered nanostructures was explored as an advanced MRI contrast agent.
Removal of J-coupling peak distortion in PGSE experiments
Publisher: Elsevier BV
Date: 08-2008
DOI: 10.1016/J.JMR.2008.05.006
Abstract: Peak distortion caused by homonuclear J-coupling is a major problem that limits the utility of the pulsed-field gradient spin-echo (PGSE) method for studying translational diffusion. This unwanted effect can be removed by incorporation of anti-phase magnetization purging pulse elements at the end of the spin-echo sequence. Three methods, namely, trim-pulse, homospoil pulse gradient and chirp based z-filter were evaluated as potential candidates for an improved NMR diffusion method that is less sensitive to J-coupling peak distortion. The chirp based z-filter was found to be excellent in suppressing anti-phase magnetization while leaving the in-phase magnetization basically intact in spin-echo and stimulated-echo based experiments. The incorporation of chirp based z-filter into PGSE could allow diffusion analysis that would otherwise be impossible by conventional means.
Translational and rotational motion of isolated water molecules in nitromethane studied using 17O NMR
Publisher: AIP Publishing
Date: 09-2000
DOI: 10.1063/1.1287421
Abstract: Hydrogen bonding plays an enormous role in determining the solution properties of liquid water. In the present study, the translational diffusion and the reorientational correlation times of isolated water (H2 17O) molecules dissolved in nitromethane were studied using O17 NMR measurements in the temperature range of 260–314 K. It was found that the water diffusion coefficient was considerably faster than in pure water at the same temperature. Further, the activation energy for the translational motion of the water was about 10 kJ mol−1, which was the same as that of the (solvent) nitromethane. However, the activation energy for the reorientational motion of the water was significantly less at 7.7 kJ mol−1. In this study we show that the motions of the isolated water molecules behave significantly different than water molecules in pure water due to the absence of hydrogen bonding to nearby water molecules.
Erratum to: Use of diffusion magnetic resonance imaging to correlate the developmental changes in grape berry tissue structure with water diffusion patterns[ Plant Methods (2014); 4(10),35. doi 10.1186/1746-4811-10-35.
Publisher: Springer Science and Business Media LLC
Date: 27-01-2016
Ice nucleation activity in various tissues of Rhododendron flower buds: Their relevance to extraorgan freezing
Publisher: Frontiers Media SA
Date: 25-03-2015
Jump-and-return sandwiches: A new family of binomial-like selective inversion sequences with improved performance
Publisher: Elsevier BV
Date: 03-2018
DOI: 10.1016/J.JMR.2018.01.008
Abstract: A new family of binomial-like inversion sequences, named jump-and-return sandwiches (JRS), has been developed by inserting a binomial-like sequence into a standard jump-and-return sequence, discovered through use of a stochastic Genetic Algorithm optimisation. Compared to currently used binomial-like inversion sequences (e.g., 3-9-19 and W5), the new sequences afford wider inversion bands and narrower non-inversion bands with an equal number of pulses. As an ex le, two jump-and-return sandwich 10-pulse sequences achieved 95% inversion at offsets corresponding to 9.4% and 10.3% of the non-inversion band spacing, compared to 14.7% for the binomial-like W5 inversion sequence, i.e., they afforded non-inversion bands about two thirds the width of the W5 non-inversion band.
195Pt NMR—theory and application
Publisher: Royal Society of Chemistry (RSC)
Date: 2007
DOI: 10.1039/B606190G
Abstract: This critical review highlights the progress in (195)Pt NMR over the last 25 years. In particular, some of the recent applications of (195)Pt NMR in catalytic and mechanistic studies, intermetallics and drug binding studies are discussed. (195)Pt NMR chemical shifts obtained from both theoretical studies and experiments are presented for Pt(0), Pt(II), Pt(III) and Pt(IV) complexes. (195)Pt coupling with various nuclei (viz. coupling constants) have also been collected in addition to data on (195)Pt relaxation. The latest developments in the theoretical knowledge and experimental advances have made (195)Pt NMR into a rich source of information in many fields. (164 references.).
NMR Versatility
Publisher: Springer International Publishing
Date: 24-12-2018
Suppression of background gradients in (B0 gradient-based) NMR diffusion experiments
Publisher: Wiley
Date: 2007
DOI: 10.1002/CMR.A.20092
Diffusion Studies of Phenylenediamine Isomers in Water-Monohydric-Alcohol Systems
Publisher: CSIRO Publishing
Date: 2014
DOI: 10.1071/CH13717
Abstract: The study of isomer diffusion provides useful information regarding solvent effects for mixture analysis. Isomers, particularly those with similar hydrodynamic radii, provide a mechanism for probing solute–solvent interactions. Here nuclear magnetic resonance was used to measure the self-diffusion of phenylenediamine isomers in various water–monohydric-alcohol (i.e. methanol, ethanol, 1-propanol, and tert-butanol) solvents. These systems allowed the effect of solvent modulation on isomer diffusion to be examined. It was found that the resonances of phenylenediamine isomers in a mixture were separable via diffusion, with the separation becoming greater at higher concentration of monohydric-alcohols. Unlike previously shown for dihydroxybenzene isomers, all three phenylenediamine isomers were differentiable via diffusion.
Self-diffusion coefficients of lithium, anion, polymer, and solvent in polymer gel electrolytes measured using7Li, 19F, and1H pulsed-gradient spin-echo NMR
Publisher: Elsevier BV
Date: 2000
Spectroscopic investigations on the interactions of potent platinum(II) anticancer agents with bovine serum albumin
Publisher: Springer Science and Business Media LLC
Date: 11-05-2012
Diffusion Studies of Dihydroxybenzene Isomers in Water–Alcohol Systems
Publisher: American Chemical Society (ACS)
Date: 21-02-2013
DOI: 10.1021/JP311044A
Abstract: Nuclear magnetic resonance diffusion studies can be used to identify different compounds in a mixture. However, because the diffusion coefficient is primarily dependent on the effective hydrodynamic radius, it is particularly difficult to resolve compounds with similar size and structure, such as isomers, on the basis of diffusion. Differential solution interactions between species in certain solutions can afford possibilities for separation. In the present study, the self-diffusion of the three isomers of dihydroxybenzene (i.e., (1,2-) catechol, (1,3-) resorcinol, and (1,4-) hydroquinone) was studied in water, aqueous monohydric alcohols (i.e., ethanol, 1-propanol, tert-butanol), and aqueous ethylene glycol. These systems allowed the effects of isomerism and differential solvent interactions on diffusion to be examined. It was found that, while in aqueous solution these isomers had the same diffusion coefficient, in water-monohydric alcohol systems the diffusion coefficient of catechol differed from those of resorcinol and hydroquinone. The separation was found to increase at higher concentrations of monohydric alcohols. The underlying chemical reasons for these differences were investigated.
Effect of placental growth factor in models of experimental pre‐eclampsia and trophoblast invasion
Publisher: Wiley
Date: 07-10-2019
Abstract: Placental growth factor (PlGF) is decreased in early gestation of pregnant women who subsequently develop pre-ecl sia. In this study, pre-emptive treatment with PlGF to prevent pre-ecl sia was evaluated in an in vivo rodent model of experimental pre-ecl sia (EPE) induced by TNF-α and in an in vitro model of human first-trimester trophoblast invasion. Pregnant C57/BL6 mice were treated with recombinant mouse placental growth factor-2 (rmPlGF-2) 100 μg/kg/day IP from gestational day (gd) 10. Animals had EPE induced by continuous TNF-α infusion on gd 13 and were subject to either continuous blood pressure monitoring by radiotelemetry throughout pregnancy or live placenta T
An NMR and ionic conductivity study of ion dynamics in liquid poly(ethylene oxide)-based electrolytes doped with LiN(SO2CF3)2
Publisher: American Chemical Society (ACS)
Date: 20-12-2002
DOI: 10.1021/JP013035+
Visualizing the postembryonic development of Sarcophaga peregrina (flesh fly) by NMR microscopy
Publisher: Wiley
Date: 12-1999
J -compensated PGSE: an improved NMR diffusion experiment with fewer phase distortions
Publisher: Wiley
Date: 08-12-2010
DOI: 10.1002/MRC.2555
Abstract: Peak distortion caused by homonuclear (1)H J-coupling is a major problem in many spin-echo-based experiments such as pulsed gradient spin-echo (PGSE) experiments. Although peak phase distortions can be lessened by the incorporation of anti-phase purging sequences, the sensitivity is substantially decreased. Techniques for lessening the effect of homonuclear J-coupling evolution in spin-echo-based experiments have been investigated. Two potentially useful candidates include a J-compensated inversion sequence that is efficient over a wide range of J-coupling values and a pulse sequence that refocuses homonuclear J-evolution during the spin-echo. The latter was found to work superbly on s les containing two spin (AX or AB) systems and still provided significant advantage over the standard method on s les containing more complicated spin systems. Implementation of this J-refocusing technique into a PGSE-type experiment (J-PGSE) leads to dramatic improvement of spectra and easier data analysis. The J-PGSE sequence should find applications in many diffusion studies where the PGSE-type method is required and should be a viable alternative to PGSTE especially in dilute s les due to its enhanced sensitivity.
Dipolar relaxation revisited: A complete derivation for the two spin case
Publisher: Wiley
Date: 03-2015
DOI: 10.1002/CMR.A.21334
Ionic conduction and self-diffusion near infinitesimal concentration in lithium salt-organic solvent electrolytes
Publisher: AIP Publishing
Date: 08-2000
DOI: 10.1063/1.482004
Abstract: The Debye–Hückel–Onsager and Nernst–Einstein equations, which are based on two different conceptual approaches, constitute the most widely used equations for relating ionic conduction to ionic mobility. However, both of these classical (simple) equations are predictive of ionic conductivity only at very low salt concentrations. In the present work the ionic conductivity of four organic solvent-lithium salt-based electrolytes were measured. These experimental conductivity values were then contrasted with theoretical values calculated using the translational diffusion (also known as self-diffusion or intradiffusion) coefficients of all of the species present obtained using pulsed-gradient spin–echo (1H, F19 and Li7) nuclear magnetic resonance self-diffusion measurements. The experimental results verified the applicability of both theoretical approaches at very low salt concentrations for these particular systems as well as helping to clarify the reasons for the ergence between theory and experiment. In particular, it was found that the correspondence between the Debye–Hückel–Onsager equation and experimental values could be improved by using the measured solvent self-diffusion values to correct for salt-induced changes in the solution viscosity. The concentration dependence of the self-diffusion coefficients is discussed in terms of the Jones–Dole equation.
Protein association studied by NMR diffusometry
Publisher: Elsevier BV
Date: 04-2006
Characterization of Chloride Ion Binding to Human Serum Albumin Using Cl NMR Null Point Spectral Analysis
Publisher: American Chemical Society (ACS)
Date: 02-1993
DOI: 10.1021/JA00056A039
Trends in HIV/AIDS morbidity and mortality in Eastern Mediterranean countries, 1990–2015: findings from the Global Burden of Disease 2015 study
Publisher: Springer Science and Business Media LLC
Date: 03-08-2017
Microscopic diffusivity compartmentation in formalin-fixed prostate tissue
Publisher: Wiley
Date: 28-12-2012
DOI: 10.1002/MRM.23244
Abstract: MR microimaging at 16.4 T with 40-μm isotropic voxels was used to investigate compartmentation of water diffusion in formalin-fixed prostate tissue. Ten tissue s les (~ 28 mm(3) each) from five organs were imaged. The mean diffusivity of epithelial, stromal, and ductal/acinar compartments was estimated by two methods: (1) manual region of interest selection and (2) Gaussian fitting of voxel diffusivity histograms. For the region of interest-method, the means of the tissue s le compartment diffusivities were significantly different (P < 0.001): 0.54 ± 0.05 μm(2)/ms for epithelium-containing voxels, 0.91 ± 0.17 μm(2)/ms for stroma, and 2.20 ± 0.04 μm(2)/ms for saline-filled ducts. The means from the histogram method were also significantly different (P < 0.001): 0.45 ± 0.08 μm(2)/ms for epithelium-containing voxels, 0.83 ± 0.16 μm(2)/ms for stroma, 2.21 ± 0.02 μm(2)/ms for duct. Estimated partial volumes of epithelial, stromal, and ductal/acinar compartments in a "tissue only" subvolume of each s le were significantly different (P < 0.02) between cancer and normal tissue for all three compartments. It is concluded that the negative correlation between apparent diffusion coefficient and cancer Gleason grade observed in vivo results from an increase of partial volume of epithelial tissue and concomitant decrease of stromal tissue and ductal space.
Recent advances in NMR diffusion techniques for studying drug binding
Publisher: CSIRO Publishing
Date: 2003
DOI: 10.1071/CH03128
Abstract: Characterizing the binding of ligands to macromolecular receptors in solution is important to many areas of chemistry, biology, and nanobiotechnology, but perhaps most notably to drug development. NMR has proven to be particularly useful for such studies, but the systems studied have generally been restricted to model systems with dubious physiological relevance. This paper reviews the use of NMR diffusion measurements to study drug binding and two recent advances that enable measurements to be conducted in more sensitive higher-field NMR spectrometers in non-deuterated aqueous s les.
Sexual selection predicts brain structure in dragon lizards
Publisher: Wiley
Date: 21-10-2016
DOI: 10.1111/JEB.12984
Abstract: Phenotypic traits such as ornaments and armaments are generally shaped by sexual selection, which often favours larger and more elaborate males compared to females. But can sexual selection also influence the brain? Previous studies in vertebrates report contradictory results with no consistent pattern between variation in brain structure and the strength of sexual selection. We hypothesize that sexual selection will act in a consistent way on two vertebrate brain regions that directly regulate sexual behaviour: the medial preoptic nucleus (MPON) and the ventromedial hypothalamic nucleus (VMN). The MPON regulates male reproductive behaviour whereas the VMN regulates female reproductive behaviour and is also involved in male aggression. To test our hypothesis, we used high-resolution magnetic resonance imaging combined with traditional histology of brains in 14 dragon lizard species of the genus Ctenophorus that vary in the strength of precopulatory sexual selection. Males belonging to species that experience greater sexual selection had a larger MPON and a smaller VMN. Conversely, females did not show any patterns of variation in these brain regions. As the volumes of both these regions also correlated with brain volume (BV) in our models, we tested whether they show the same pattern of evolution in response to changes in BV and found that the do. Therefore, we show that the primary brain nuclei underlying reproductive behaviour in vertebrates can evolve in a mosaic fashion, differently between males and females, likely in response to sexual selection, and that these same regions are simultaneously evolving in concert in relation to overall brain size.
Delivery of polymeric nanostars for molecular imaging and endoradiotherapy through the enhanced permeability and retention (EPR) effect
Publisher: Ivyspring International Publisher
Date: 2020
DOI: 10.7150/THNO.36777
Ion diffusion restricted by time-dependent barriers in a viscous polyethylene-based liquid electrolyte
Publisher: American Chemical Society (ACS)
Date: 25-10-2003
DOI: 10.1021/MA035265N
An improved approach to calibrating high magnetic field gradients for pulsed field gradient experiments
Publisher: Elsevier BV
Date: 09-2008
DOI: 10.1016/J.JMR.2008.05.015
Abstract: Probes capable of generating short high intensity pulsed magnetic field gradients are commonly used in diffusion studies of systems with very short T(2). Traditional methods of calibrating magnetic field gradients present unique challenges at ultrahigh field strengths and are often inapplicable. Currently the most accurate method of determining magnetic gradient strength is to use the known diffusion coefficient of a standard s le and determine gradient strength from the echo attenuation plot of a diffusion experiment, however, there are problems with finding suitable standards for high intensity gradients. Here, we show that molecules containing at least two receptive nuclei (i.e. one with high and one with low gyromagnetic ratios) are excellent systems for calibrating high intensity gradients.
Restricted diffusion in annular geometrical pores
Publisher: AIP Publishing
Date: 05-03-2013
DOI: 10.1063/1.4793525
Abstract: Nuclear magnetic resonance (NMR) diffusion (including diffusion MRI) experiments are only as powerful as the models used to analyse the NMR diffusion data. A major problem, especially with measurements on biological systems, is that the existing models are only very poor approximations of cellular shape. Here, diffusion propagators and pulsed gradient spin-echo attenuation equations are derived in the short gradient pulse limit for diffusion within the annular region of a concentric cylinder of finite length and, similarly, within the annular region of a concentric sphere. The models include the possibility of relaxation at the boundaries and, in the case of the concentric cylinder, having the cylinder arbitrarily oriented with respect to the direction of the applied field gradient. The two models are also of interest due to their direct analogy to optical double slit diffraction. Also expressions for the mean square displacements, which are very useful information for determining the diffusion coefficient within these complex geometries, are obtained as well as for the limiting cases of diffusion on cylindrical and spherical shells and in a ring.
Controlled Diffusion of Photoswitchable Receptors by Binding Antielectrostatic Phosphate Oligomers
Publisher: American Chemical Society (ACS)
Date: 15-05-2020
DOI: 10.26434/CHEMRXIV.12298919
Abstract: Dihydrogen phosphate anions are found to spontaneously associate into anti-electrostatic oligomers via hydrogen bonding interactions at millimolar concentrations in DMSO. Diffusion NMR measurements supported formation of these oligomers, which can be bound by photoswitchable anion receptors to form large bridged assemblies of approximately three times the volume of the unbound receptor. Photoisomerization of the oligomer-bound receptor causes a decrease in diffusion coefficient of up to 16%, corresponding to a 70% increase in effective volume. This new approach to external control of diffusion opens prospects in controlling molecular transport.
NMR diffusion and relaxation studies of 2-nitroimidazole and albumin interactions
Publisher: Elsevier BV
Date: 03-2018
DOI: 10.1016/J.SAA.2017.12.016
Abstract: Nitroimidazole derivatives are of current interest in the development of hypoxia targeting agents and show potential in the establishment of quantitative measures of tumor hypoxia. In this study, the binding of 2-nitroimidazole to albumin was probed using NMR diffusion and relaxation measurements. Binding studies were conducted at three different protein concentrations (0.23, 0.30 and 0.38mM) with drug concentrations ranging from 0.005-0.16M at 298K. Quantitative assessments of the binding model were made by evaluating the number of binding sites, n, and association constant, K. These were determined to be 21±3 and 53±4M
Errors in the Use of NMR to Test Molecular Mobility during a Chemical Reaction
Publisher: American Chemical Society (ACS)
Date: 29-03-2021
DOI: 10.26434/CHEMRXIV.14306771
Abstract: A study reported in The Journal of Physical Chemistry Letters (12 (2021) 2370) of “boosted mobility” measured by diffusion NMR experiments contains significant errors in data analysis and interpretation. We carefully reanalyzed the same data and find no evidence of boosted mobility, and we identify several sources of error.
A volumetric and intra-diffusion study of solutions of AlCl3 in two ionic liquids – [C2TMEDA][Tf2N] and [C4mpyr][Tf2N]
Publisher: Royal Society of Chemistry (RSC)
Date: 2022
DOI: 10.1039/D2CP03304F
Abstract: Ion self-diffusion coefficients in ionic liquid solutions follow the Ertl–Dullien free volume power law with concentration dependent offsets.
A new phase modulated binomial-like selective-inversion sequence for solvent signal suppression in NMR
Publisher: Wiley
Date: 22-09-2017
DOI: 10.1002/MRC.4505
Abstract: A new 8-pulse Phase Modulated binomial-like selective inversion pulse sequence, dubbed '8PM', was developed by optimizing the nutation and phase angles of the constituent radio-frequency pulses so that the inversion profile resembled a target profile. Suppression profiles were obtained for both the 8PM and W5 based excitation sculpting sequences with equal inter-pulse delays. Significant distortions were observed in both profiles because of the offset effect of the radio frequency pulses. These distortions were successfully reduced by adjusting the inter-pulse delays. With adjusted inter-pulse delays, the 8PM and W5 based excitation sculpting sequences were tested on an aqueous lysozyme solution. The 8 PM based sequence provided higher suppression selectivity than the W5 based sequence. Two-dimensional nuclear Overhauser effect spectroscopy experiments were also performed on the lysozyme s le with 8PM and W5 based water signal suppression. The 8PM based suppression provided a spectrum with significantly increased (~ doubled) cross-peak intensity around the suppressed water resonance compared to the W5 based suppression. Copyright © 2016 John Wiley & Sons, Ltd.
Shortening NMR experimental times
Publisher: Wiley
Date: 21-06-2018
DOI: 10.1002/MRC.4749
Abstract: Conventionally, arrayed nuclear magnetic resonance experiments, such as diffusion and relaxation, are performed with the same number of scans (NS) at each iteration despite the signal-to-noise ratio being more than sufficient for many of the iterations. Here, we propose a simple yet effective approach that significantly shortens experimental times by varying NS through the arrayed experiments while keeping the signal-to-noise ratio essentially the same and retaining experimental accuracy.
Environmental NMR: Diffusion Ordered Spectroscopy Methods
Publisher: John Wiley & Sons, Ltd
Date: 06-03-1996
NMR diffusion measurements of strong signals: The PGSE-Q-switch experiment
Publisher: Wiley
Date: 08-11-2002
DOI: 10.1002/MRC.1113
Evaluating the Stability of Cellulose Nanofiber Pickering Emulsions Using MRI and Relaxometry
Publisher: American Chemical Society (ACS)
Date: 07-03-2023
Ice nucleation activity in plants: The distribution, characterization, and their roles in cold hardiness mechanisms
Publisher: Springer Singapore
Date: 2018
DOI: 10.1007/978-981-13-1244-1_6
Abstract: Control of freezing in plant tissues is a key issue in cold hardiness mechanisms. Yet freeze-regulation mechanisms remain mostly unexplored. Among them, ice nucleation activity (INA) is a primary factor involved in the initiation and regulation of freezing events in plant tissues, yet the details remain poorly understood. To address this, we developed a highly reproducible assay for determining plant tissue INA and noninvasive freeze visualization tools using MRI and infrared thermography. The results of visualization studies on plant freezing behaviors and INA survey of over 600 species tissues show that (1) freezing-sensitive plants tend to have low INA in their tissues (thus tend to transiently supercool), while wintering cold-hardy species have high INA in some specialized tissues and (2) the high INA in cold-hardy tissues likely functions as a freezing sensor to initiate freezing at warm subzero temperatures at appropriate locations and timing, resulting in the induction of tissue-/species-specific freezing behaviors (e.g., extracellular freezing, extraorgan freezing) and the freezing order among tissues: from the primary freeze to the last tissue remaining unfrozen (likely INA level dependent). The spatiotemporal distributions of tissue INA, their characterization, and functional roles are detailed. INA assay principles, anti-nucleation activity (ANA), and freeze visualization tools are also described.
Some Recent Developments in NMR Approaches for Studying Liquid Molecular Dynamics and Their Biological Applications
Publisher: Wiley
Date: 12-1992
Time-course study of grape berry split using diffusion magnetic resonance imaging
Publisher: Hindawi Limited
Date: 16-10-2015
DOI: 10.1111/AJGW.12184
A 35Cl and 37Cl NMR study of chloride binding to the erythrocyte anion transport protein
Publisher: Elsevier BV
Date: 07-1991
DOI: 10.1016/0301-4622(91)80030-U
Abstract: Band 3, the erythrocyte anion transport protein, mediates the one-for-one exchange of bicarbonate and chloride ions across the membrane and consequently plays an important role in respiration. Binding to the protein forms the first step in the translocation of the chloride across the membrane. 35Cl and 37Cl NMR relaxation measurements at various field strengths were used to study chloride binding to the protein in the presence and absence of the transport inhibitor 4,4'-dinitrostilbene-2,2'-disulfonate. Significant differences occurred in the NMR relaxation rates depending on whether the inhibitor was present or not. The results indicate that the rate of chloride association and dissociation at each external binding site occurs on a time scale of less than or equal to 5 microseconds. This implies that the transmembrane flux is not limited by the rate of chloride binding to the external chloride binding site of band 3. The rotational correlation-time of chloride bound to band 3 was found to be greater than 20 ns with a quadrupole coupling constant of approximately 2 MHz.
Lysozyme aggregation and solution properties studied using PGSE NMR diffusion measurements
Publisher: American Chemical Society (ACS)
Date: 30-11-1999
DOI: 10.1021/JA992265N
Comment on “Boosted Molecular Mobility During Common Chemical Reactions
Publisher: American Chemical Society (ACS)
Date: 05-10-2020
DOI: 10.26434/CHEMRXIV.13023164.V1
Abstract: The apparent “boosted mobility” observed by nuclear magnetic resonance (NMR) diffusion measurements is the result of a known artefact. When signal intensities are changing during an NMR diffusion measurement for reasons other than diffusion, the use of monotonically increasing gradient litudes produces erroneous diffusion coefficient values. We show that no boosted molecular mobility is observed when shuffled gradient litudes are applied.
Erratum to: Hydrogen isotope replacement changes hydration and large scale structure, but not small scale structure, of agarose hydrogel networks
Publisher: Springer Science and Business Media LLC
Date: 07-2019
DOI: 10.1140/EPJE/I2019-11860-5
Abstract: With reference to eq. (5) in the original article, the authors have neglected to specify the description of some terms in the text. They correct the mistake in the present erratum.
Factors Affecting the Solid-State Polymerization of 1,4-Bis(1,3-octadecadiynyl)benzene to a Polydiacetylene
Publisher: American Chemical Society (ACS)
Date: 07-1995
DOI: 10.1021/MA00119A029
NMR q-space imaging of macroscopic pores using singlet spin states
Publisher: Elsevier BV
Date: 06-2010
DOI: 10.1016/J.JMR.2010.03.010
Abstract: NMR q-space imaging is a powerful non-invasive technique used to determine structural characteristics of pores in applications ranging from medical to material science. To date, the application of q-space imaging has primarily been limited to microscopic pores in part because of limitations of the effective observation time due to relaxation. Here we report on the use of singlet spin states for NMR q-space imaging, which allow significantly greater observation times. This opens the way for studying larger pores in materials such as biological tissue, emulsions, and rocks.
Self-diffusion coefficients of some hydrocarbons in water: Measurements and scaling relations
Publisher: American Chemical Society (ACS)
Date: 26-05-2000
DOI: 10.1021/JP000716G
Design and Construction of a Pulsed Field‐Gradient NMR Probe for a High‐Field Superconducting Magnet
Publisher: Wiley
Date: 04-1994
MRI Detection of Hepatic N-Acetylcysteine Uptake in Mice
Publisher: MDPI AG
Date: 31-08-2022
DOI: 10.3390/BIOMEDICINES10092138
Abstract: This proof-of-concept study looked at the feasibility of using a thiol–water proton exchange (i.e., CEST) MRI contrast to detect in vivo hepatic N-acetylcysteine (NAC) uptake. The feasibility of detecting NAC-induced glutathione (GSH) biosynthesis using CEST MRI was also investigated. The detectability of the GSH amide and NAC thiol CEST effect at B0 = 7 T was determined in phantom experiments and simulations. C57BL/6 mice were injected intravenously (IV) with 50 g L−1 NAC in PBS (pH 7) during MRI acquisition. The dynamic magnetisation transfer ratio (MTR) and partial Z-spectral data were generated from the acquisition of measurements of the upfield NAC thiol and downfield GSH amide CEST effects in the liver. The 1H-NMR spectroscopy on aqueous mouse liver extracts, post-NAC-injection, was performed to verify hepatic NAC uptake. The dynamic MTR and partial Z-spectral data revealed a significant attenuation of the mouse liver MR signal when a saturation pulse was applied at −2.7 ppm (i.e., NAC thiol proton resonance) after the IV injection of the NAC solution. The 1H-NMR data revealed the presence of hepatic NAC, which coincided strongly with the increased upfield MTR in the dynamic CEST data, providing strong evidence that hepatic NAC uptake was detected. However, this MTR enhancement was attributed to a combination of NAC thiol CEST and some other upfield MT-generating mechanism(s) to be identified in future studies. The detection of hepatic GSH via its amide CEST MRI contrast was inconclusive based on the current results.
NMR imaging and diffusion
Publisher: Springer Science and Business Media LLC
Date: 19-09-7023
Examination of Cucurbit[7]uril and Its Host−Guest Complexes by Diffusion Nuclear Magnetic Resonance
Publisher: American Chemical Society (ACS)
Date: 02-2008
DOI: 10.1021/JP709847P
Abstract: The self-diffusion of cucurbit[7]uril (CB[7]) and its host-guest complexes in D2O has been examined using pulsed gradient spin-echo nuclear magnetic resonance spectroscopy. CB[7] diffuses freely at a concentration of 2 mM with a diffusion coefficient (D) of 3.07 x 10(-10) m(2) s(-1). At saturation (3.7 mM), CB[7] diffuses more slowly (D = 2.82 x 10(-10) m(2) s(-1)) indicating that it partially self-associates. At concentrations between 2 and 200 mM, CsCl has no effect on the diffusion coefficient of CB[7] (1 mM). Conversely, CB[7] (2 mM) significantly affects the diffusion of 133Cs+ (1 mM), decreasing its diffusion coefficient from 1.86 to 0.83 x 10(-9) m(2) s(-1). Similar changes in the rate of diffusion of other alkali earth metal cations are observed upon the addition of CB[7]. The diffusion coefficient of 23Na+ changes from 1.26 to 0.90 x 10(-9) m(2) s(-1) and 7Li+ changes from 3.40 to 3.07 x 10(-9) m(2) s(-1). In most cases, encapsulation of a variety of inorganic and organic guests within CB[7] decreases their rates of diffusion in D2O. For instance, the diffusion coefficient of the dinuclear platinum complex trans-[[PtCl(NH3)2}2mu-dpzm](2+) (where dpzm is 4,4'-dipyrazolylmethane) decreases from 4.88 to 2.95 x 10(-10) m(2) s(-1) upon encapsulation with an equimolar concentration of CB[7].
Modeling diffusion in restricted systems using the heat kernel expansion
Publisher: AIP Publishing
Date: 17-06-2010
DOI: 10.1063/1.3451124
Abstract: The averaged return-to-origin probability of finding a diffusing particle within a volume or in the neighborhood of the surface of a bounded region can be separated into a volume and a surface integral of the corresponding probability densities. However with the usual treatments (e.g., the commonly encountered diffusion propagator approach) there is no clear method to separate the integration of the diffusion propagators in each domain. Here we propose a general procedure based on applying the heat kernel expansion in restricted diffusion problems for the Green’s function of the diffusion equation on an arbitrary region with an arbitrary boundary condition. We apply this method to the treatment of surface reaction rate in a sphere subject to the reflecting boundary condition. We determine that the rate of diffusion of a particle from the interior to the surface of the sphere changes by the square root of time plus some extra correction terms. Further, we are able to relate the diffusion propagator to the invariant properties of the region. Also in this approach we investigate how the heat kernel expansion can be applied to the problem of determining the return-to-origin probability, where we obtain a more precise result for the expansion of this probability in the case of a sphere. The advantage of this method lies in its generality and applicability to any geometrical boundary configuration and any kind of boundary condition.
Self-assembled supramolecular cages containing dinuclear ruthenium(II) crossMark polypyridyl complexes
Publisher: Elsevier BV
Date: 03-2017
Evidence for Concerted and Mosaic Brain Evolution in Dragon Lizards
Publisher: S. Karger AG
Date: 2017
DOI: 10.1159/000478738
Abstract: The brain plays a critical role in a wide variety of functions including behaviour, perception, motor control, and homeostatic maintenance. Each function can undergo different selective pressures over the course of evolution, and as selection acts on the outputs of brain function, it necessarily alters the structure of the brain. Two models have been proposed to explain the evolutionary patterns observed in brain morphology. The concerted brain evolution model posits that the brain evolves as a single unit and the evolution of different brain regions are coordinated. The mosaic brain evolution model posits that brain regions evolve independently of each other. It is now understood that both models are responsible for driving changes in brain morphology however, which factors favour concerted or mosaic brain evolution is unclear. Here, we examined the volumes of the 6 major neural sub isions across 14 species of the agamid lizard genus i Ctenophorus /i (dragons). These species have erged multiple times in behaviour, ecology, and body morphology, affording a unique opportunity to test neuroevolutionary models across species. We assigned each species to an ecomorph based on habitat use and refuge type, then used MRI to measure total and regional brain volume. We found evidence for both mosaic and concerted brain evolution in dragons: concerted brain evolution with respect to body size, and mosaic brain evolution with respect to ecomorph. Specifically, all brain sub isions increase in volume relative to body size, yet the tectum and rhombencephalon also show opposite patterns of evolution with respect to ecomorph. Therefore, we find that both models of evolution are occurring simultaneously in the same structures in dragons, but are only detectable when examining particular drivers of selection. We show that the answer to the question of whether concerted or mosaic brain evolution is detected in a system can depend more on the type of selection measured than on the clade of animals studied.
Spatial and temporal control of drug release through pH and alternating magnetic field induced breakage of Schiff base bonds
Publisher: Royal Society of Chemistry (RSC)
Date: 2014
DOI: 10.1039/C4PY00150H
Abstract: A novel theranostic controlled drug delivery platform that binds the drug to the nanocarrier by utilising Schiff base bonds to achieve high spatial and temporal control over drug release.
Enhanced Diffusion of Molecular Catalysts is Due to Convection
Publisher: Wiley
Date: 12-11-2019
Abstract: Intriguing reports of enhanced diffusion in enzymes and molecular catalysts have spurred significant interest in experimental and theoretical investigations, and the mechanism of this phenomenon is the topic of lively debate. Here we use time‐resolved diffusion NMR methods to measure the diffusion coefficients ( D ) of small molecule species involved in chemical reactions with high temporal resolution. We show the enhanced diffusion of small molecules cannot be explained by reaction velocity, and that apparent measurements of enhanced diffusion by small molecules appear to be caused by bulk fluid flow processes such as convection.
Response to Comment on “Following Molecular Mobility during Chemical Reactions: No Evidence for Active Propulsion” and “Molecular Diffusivity of Click Reaction Components: The Diffusion Enhancement Question”
Publisher: American Chemical Society (ACS)
Date: 03-08-2022
DOI: 10.1021/JACS.2C02830
Abstract: In their Comment (DOI: 10.1021/jacs.2c02965) on two related publications by our groups (
Probing solute–solvent interactions using difluorobenzene isomers in water–monohydric-alcohol mixtures
Publisher: Elsevier BV
Date: 10-2014
Solution dynamics in aqueous monohydric alcohol systems
Publisher: American Chemical Society (ACS)
Date: 24-05-2003
DOI: 10.1021/JP027257Z
Stress-Induced Grey Matter Loss Determined by MRI Is Primarily Due to Loss of Dendrites and Their Synapses
Publisher: Springer Science and Business Media LLC
Date: 09-11-2013
DOI: 10.1007/S12035-012-8365-7
Abstract: Stress, unaccompanied by signs of post-traumatic stress disorder, is known to decrease grey matter volume (GMV) in the anterior cingulate cortex (ACC) and hippoc us but not the amygdala in humans. We sought to determine if this was the case in stressed mice using high-resolution magnetic resonance imaging (MRI) and to identify the cellular constituents of the grey matter that quantitatively give rise to such changes. Stressed mice showed grey matter losses of 10 and 15 % in the ACC and hippoc us, respectively but not in the amygdala or the retrosplenial granular area (RSG). Concurrently, no changes in the number or volumes of the somas of neurons, astrocytes or oligodendrocytes were detected. A loss of synaptic spine density of up to 60 % occurred on different-order dendrites in the ACC and hippoc us (CA1) but not in the amygdala or RSG. The loss of spines was accompanied by decreases in cumulative dendritic length of neurons of over 40 % in the ACC and hippoc us (CA1) giving rise to decreases in volume of dendrites of 2.6 mm(3) for the former and 0.6 mm(3) for the latter, with no change in the amygdala or RSG. These values are similar to the MRI-determined loss of GMV following stress of 3.0 and 0.8 mm(3) in ACC and hippoc us, respectively, with no changes in the amygdala or RSG. This quantitative study is the first to relate GMV changes in the cortex measured with MRI to volume changes in cellular constituents of the grey matter.
NMR study of the structure and self‐association of core peptide in aqueous solution and DPC micelles
Publisher: Wiley
Date: 2011
DOI: 10.1002/BIP.21423
Abstract: Core peptide is a hydrophobic peptide derived from the T-cell antigen receptor-alpha chain (TCR-alpha) transmembrane region with therapeutic potential. The mechanism by which the peptide inserts into the membrane, including any requirements to change conformational or association states during the insertion, is unclear. Here, the self-association and secondary structure of Core peptide in aqueous solution and in dodecylphosphocholine (DPC) micelles were examined using various nuclear magnetic resonance (NMR) techniques. NMR diffusion measurements were performed on 0.05, 1, and 5 mM Core peptide in D2O. These s les had pH values varying from 3 to 4. A constant measured diffusion coefficient of 2 X 10(-10) m2 s(-1) was observed in these s les indicating that Core peptide was monomeric. Multidimensional NMR experiments (i.e., TOCSY and NOESY) revealed the formation of beta-strands in water at low pH and random coil in DPC micelles. The results of this study reveal that at relatively low pH, the insertion mechanism must involve Core peptide in the monomeric state but it undergoes a conformational transition during membrane insertion.
Is It Time to Forgo the Use of the Terms “Spin–Lattice” and “Spin–Spin” Relaxation in NMR and MRI?
Publisher: American Chemical Society (ACS)
Date: 15-07-2021
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