ORCID Profile
0000-0003-2127-8792
Current Organisations
University of New Brunswick
,
University of Notre Dame
,
University of Western Ontario
,
The University of Auckland
,
The University of Manitoba
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Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C9SM00932A
Abstract: Explaining antimicrobial battacin lipopeptides by investigating the solution structure – the propensity to aggregate may have a role in a declined antimicrobial activity.
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/D0SM01071E
Abstract: Increased water solubility and long-range intermolecular ordering have been introduced into the fluorescent organic molecule thiophene-diketopyrrolopyrrole via its conjugation to the octapeptide HEFISTAH, derived from a protein–protein β-interface.
Publisher: American Chemical Society (ACS)
Date: 02-12-2009
DOI: 10.1021/LA802865Z
Publisher: American Vacuum Society
Date: 06-2017
DOI: 10.1116/1.4984010
Abstract: The authors present surface engineering modifications through chemistry of poly(methylmethacrylate) (PMMA) that have dramatic effects on the result of surface-bound fluorescence immunoassays, both for specific and nonspecific signals. The authors deduce the most important effect to be clustering of antibodies on the surface leading to significant self-quenching. Secondary effects are attributable to the formation of sparse multilayers of antibody. The authors compare PMMA as an antibody support surface with ultraviolet-ozone oxidized PMMA and also to substrates that were, after the oxidation, surface modified by a four-unit poly(ethyleneglycol) carboxylic acid (PEG4), a branched tricarboxylic acid, and a series of carboxylic acid-terminated dendrimers, from generation 1.5 to 5.5. Fluorescence immunoassay and neutron reflectometry were used to compare the apparent antibody surface loading, antigen binding and nonspecific binding on these various surfaces using anti-human IgG as a model antibody, chemically coupled to the surface by amide formation. Simple physical adsorption of the antibody on PMMA resulted in a thick antibody multilayer with small antigen binding capacity. On the carboxylated surfaces, with chemical coupling, a simple monolayer was formed. The authors deduce that antibody clustering was driven by conformational inflexibility and high carboxylate density. The PEG4-modified surface was the most conformationally flexible. The dendrimer-modified interfaces showed a collapse and densification. In fluorescence immunoassay, the optimal combination of high specific and low nonspecific fluorescence signal was found for the G3.5 dendrimer.
Publisher: Elsevier BV
Date: 12-2017
DOI: 10.1016/J.JINORGBIO.2017.08.032
Abstract: The non-haem Fe(II) and 2-oxoglutarate (2OG)-dependent oxygenases belong to a superfamily of structurally-related enzymes that play important biological roles in plants, microorganisms and animals. Structural, mechanistic and functional studies of 2OG oxygenases require efficient and effective biophysical tools. Nuclear magnetic resonance (NMR) spectroscopy is a useful tool to study this enzyme superfamily. It has been applied to obtain information about enzyme kinetics, identify and characterise 2OG oxygenase-catalysed oxidation products, elucidate the catalytic mechanism, monitor ligand binding and study protein dynamics. This review summarises the types of information that NMR spectroscopy can provide in the studies of 2OG oxygenases, highlights the advantages of the technique and describes its drawbacks.
Publisher: Royal Society of Chemistry (RSC)
Date: 2011
DOI: 10.1039/C0SM01284J
Publisher: Springer Science and Business Media LLC
Date: 28-01-2023
DOI: 10.1038/S41467-023-36133-8
Abstract: Injectable biomimetic hydrogels have great potential for use in regenerative medicine as cellular delivery vectors. However, they can suffer from issues relating to hypoxia, including poor cell survival, differentiation, and functional integration owing to the lack of an established vascular network. Here we engineer a hybrid myoglobin:peptide hydrogel that can concomitantly deliver stem cells and oxygen to the brain to support engraftment until vascularisation can occur naturally. We show that this hybrid hydrogel can modulate cell fate specification within progenitor cell grafts, resulting in a significant increase in neuronal differentiation. We find that the addition of myoglobin to the hydrogel results in more extensive innervation within the host tissue from the grafted cells, which is essential for neuronal replacement strategies to ensure functional synaptic connectivity. This approach could result in greater functional integration of stem cell-derived grafts for the treatment of neural injuries and diseases affecting the central and peripheral nervous systems.
Publisher: Royal Society of Chemistry (RSC)
Date: 2016
DOI: 10.1039/C5SM01530H
Abstract: β-Lg nanofibrils can be cross-linked into ordered nanotapes by the use of specific, highly methylesterified pectins.
Publisher: Royal Society of Chemistry (RSC)
Date: 2015
DOI: 10.1039/C5TB00702J
Abstract: A zein protein layer was used to mineralize thin films of calcium phosphate at the air–solution interface producing an iridescent mineral film with novel nano-morphology.
Publisher: Elsevier BV
Date: 05-2016
Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C7CE01303E
Abstract: An 11 Å mineral film above a dense prenucleation cluster subphase is shown to be the structure of the early stage of calcium phosphate nucleation from a simulated body fluid.
Publisher: Elsevier BV
Date: 2016
Publisher: American Chemical Society (ACS)
Date: 12-08-2021
Publisher: American Chemical Society (ACS)
Date: 11-07-2008
DOI: 10.1021/JP800354R
Abstract: We report observations of the changes in the surface structure of lysozyme adsorbed at the air-water interface produced by the chemical denaturant guanidinium chloride. A primary result is the durability of the adsorbed surface layer to denaturation, as compared to the molecule in the bulk solution. Data on the surface film were obtained from X-ray and neutron reflectivity measurements and modeled simultaneously. The behavior of lysozyme in G.HCl solutions was determined by small-angle X-ray scattering. For the air-water interface, determination of the adsorbed protein layer dimensions shows that at low to moderate denaturant concentrations (up to 2 mol L(-1)), there is no significant distortion of the protein's tertiary structure at the interface, as changes in the orientation of the protein are sufficient to model data. At higher denaturant concentrations, time-dependent multilayer formation occurred, indicating molecular aggregation at the surface. Methodologies to predict the protein orientation at the interface, based on amino acid residues' surface affinities and charge, were critiqued and validated against our experimental data.
Publisher: Royal Society of Chemistry (RSC)
Date: 2021
DOI: 10.1039/D1OB00355K
Abstract: In this work, the synthesis of reactive oxygen species responsive mono S -lipidated peptide hydrogels via a photoinitiated thiol–ene reaction is reported.
Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C6SM02660E
Abstract: We have simplified the structural heterogeneity of protein-polysaccharide binding by investigating protein binding to oligosaccharides. The interactions between bovine beta-lactoglobulin A (βLgA) and oligo-galacturonic acids (OGAs) with various numbers of sugar residues have been investigated with a range of biophysical techniques. We show that the βLgA-OGA interaction is critically dependent on the length of the oligosaccharide. Isothermal titration calorimetry results suggest that a minimum length of 7 or 8 sugar residues is required in order to exhibit appreciable exothermic interactions with βLgA - shorter oligosaccharides show no enthalpic interactions at any concentration ratio. When titrating βLgA into OGAs with more than 7-8 sugar residues the s le solution also became turbid with increasing amounts of βLgA, indicating the formation of macroscopic assemblies. Circular dichroism, thioflavin T fluorescence and small angle X-ray/neutron scattering experiments revealed two structural regimes during the titration. When OGAs were in excess, βLgA formed discrete assemblies upon OGA binding, and no subsequent aggregation was observed. However, when βLgA was present in excess, multi-scale structures were formed and this eventually led to the separation of the solution into two liquid-phases.
Publisher: American Chemical Society (ACS)
Date: 04-10-2022
DOI: 10.1021/ACS.LANGMUIR.2C02003
Abstract: Protein-polysaccharide composite materials have generated much interest due to their potential use in medical science and biotechnology. A comprehensive understanding of the assembly mechanism and the mesoscale architecture is needed for fabricating protein-polysaccharide composite materials with desired properties. In this study, complex assemblies were built on silica surfaces through a layer-by-layer (LbL) approach using bovine beta-lactoglobulin variant A (βLgA) and pectin as model protein and polysaccharide, respectively. We demonstrated the combined use of quartz crystal microbalance with dissipation monitoring (QCM-D) and neutron reflectometry (NR) for elucidating the assembly mechanism as well as the internal architecture of the protein-polysaccharide complexes formed at the solid-liquid interface. Our results show that βLgA and pectin interacted with each other and formed a cohesive matrix structure at the interface consisting of intertwined pectin chains that were cross-linked by βLgA-rich domains. Although the complexes were fabricated in an LbL fashion, the complexes appeared to be relatively homogeneous with βLgA and pectin molecules spatially distributed within the matrix structure. Our results also demonstrate that the density of βLgA-pectin complex assemblies increased with both the overall and local charge density of pectin molecules. Therefore, the physical properties of the protein-polysaccharide matrix structure, including density and level of hydration, can be tuned by using polysaccharides with varying charge patterns, thus promoting the development of composite materials with desired properties.
Publisher: American Chemical Society (ACS)
Date: 20-12-2002
DOI: 10.1021/LA0206920
Publisher: American Vacuum Society
Date: 09-2020
DOI: 10.1116/6.0000404
Abstract: A major challenge in understanding nanoplastic toxicity (or nanoparticles in general) lies in establishing the causal relationships between its physical properties and biological impact. This difficulty can be attributed to surface alterations that follow the formation of a biological complex around the nanoplastic, as exemplified by protein coronae. The protein corona is known to be responsible for the biological response elicited, although its own structure and attributes remain unknown. We approach this knowledge gap by independently studying the structure of soft and hard coronae using neutron scattering techniques. We investigated the formation and the structure of corona proteins (human serum albumin and lysozyme) and the resulting protein corona complexes with polystyrene nanoplastics of different sizes (20 and 200 nm) and charges. Soft corona complexes (regardless of protein type) adopted a structure where the nanoplastics were surrounded by a loose protein layer (∼2–3 protein molecules thick). Hard corona complexes formed fractal-like aggregates, and the morphology of which is known to be harmful to cellular membranes. In most cases, hard-corona coated nanoplastics also formed fractal-like aggregates in solution. Nanoplastic size affected the structures of both the protein corona and the intrinsic protein: more significant conformational change was observed in the hard corona proteins around smaller nanoparticles compared to larger ones, as the self-association forces holding the nanoplastic rotein complex together were stronger. This also implies that protein-dependent biochemical processes are more likely to be disrupted by smaller polystyrene nanoplastics, rather than larger ones.
Publisher: Elsevier BV
Date: 12-2018
Publisher: Mineralogical Society
Date: 08-2003
Abstract: Compreignacite, a naturally occurring potassium uranyl oxide hydrate, is an expected alteration product of spent nuclear fuel subjected to oxidative corrosion in the presence of water. Ion-exchange experiments were performed using natural crystals of compreignacite in a 2 M CsCl solution at 180°C for 24 h, and in a 100 ppm CsCl solution at 90°C for 14 days. Exchange of Cs into crystals of compreignacite was demonstrated by crystal-structure analysis for a crystal from 2 M solution and chemical analysis for crystals from both exchange experiments. The structure of Cs-exchanged compreignacite is hexagonal, space group P 2m, a = 14.1014 (18) Å, c = 15.127(3) Å, V = 2605.1(7) Å 2 . It was solved by direct methods and refined on the basis of F 2 for all unique reflections to a final R 1 = 6.37%. The structure determination demonstrated almost complete exchange of Cs for K in the interlayer of the structure, as confirmed by compositional analysis of the crystals, and provided the formula Cs 6 [(UO 2 ) 12 (OH) 10 O 10 ](H 2 O) 3.5 , Z = 2. The structure of Cs-exchanged compreignacite contains α-U 3 O 8 -type sheets of uranyl pentagonal bipyramids that are topologically identical, although compositionally distinct, to those in compreignacite. Compreignacite crystals placed in 100 ppm CsCl solution also incorporated substantial Cs by ion exchange. Ion exchange experiments, using Cs-exchanged compreignacite from earlier experiments, in 2 M KCl solution at 90°C for 14 days showed that compreignacite will retain significant Cs in the presence of a solution rich in K. These experiments indicate that formation of compreignacite structure-type phases in a geological repository due to alteration of nuclear waste may significantly impact upon the mobility of Cs, either by direct incorporation of Cs into growing crystals, or by exchange of Cs into earlier-formed crystals of compreignacite when they contact Cs-bearing solutions.
Publisher: American Chemical Society (ACS)
Date: 10-11-2017
DOI: 10.1021/ACS.BIOMAC.7B01245
Abstract: Six guanidine functionalized aliphatic biodegradable polycarbonates with varying molecular weights and charge densities were synthesized via postsynthesis modification of alkyne containing polycarbonates using Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) click chemistry. The concept of passive diluting group was to modify the cationic charge density of the polycarbonate without changing its hydrophilicity. Within the molecular weight range from 8000 to 30000 g mol
Publisher: American Chemical Society (ACS)
Date: 13-11-2015
DOI: 10.1021/ACS.LANGMUIR.5B02458
Abstract: Damage to cellular membranes from oxidative stress has been implicated in aging related diseases. We report the effects of oxidative damage on the structure and properties of biomimetic phospholipid membrane systems. Two oxidation methods were used, in situ oxidation initiated using Fe(II) and ascorbate, and the incorporation of a synthetic "oxidized" phospholipid, PoxnoPC, into biomimetic membranes. The biomimetic systems employed included multibilayer stacks, tethered bilayers, and phospholipid monolayers studied using a combination of reflectometry, attenuated total reflection infrared spectroscopy, electrochemical impedance spectroscopy, and neutron diffraction. We show that oxidation with Fe(II) and ascorbate caused an increase in the order of the membrane, attributed to cross-linking of the phospholipids, and a change in the electrical permeability of the membrane, but no significant impact on the thickness or completeness of the membrane. Incorporation of PoxnoPC, on the other hand, had a larger impact on the structure of the membrane. Inversion of the aldehyde-terminated truncated sn-2 chain of PoxnoPC into the head group region was observed, along with a slight decrease in the thickness and order of the membrane.
Publisher: Inderscience Publishers
Date: 2017
Publisher: Research Square Platform LLC
Date: 06-2022
DOI: 10.21203/RS.3.RS-50947/V1
Abstract: Injectable hydrogels have great potential for use in regenerative medicine as cellular delivery vectors. However, as with other cell-laden transplantable materials, they suffer from issues relating to hypoxia, including poor cell survival, differentiation, and functional integration owing to the lack of an established vascular network. Here, we have engineered a hybrid myoglobin:peptide hydrogel that can concomitantly deliver stem cells and oxygen to the brain to support engraftment until vascularisation can occur naturally. This hybrid hydrogel can modulate cell fate specification within progenitor cell grafts, resulting in a significant increase in neuronal differentiation. The addition of myoglobin to the hydrogel resulted in more extensive innervation within the host tissue from the grafted cells, which is essential for neuronal replacement strategies to ensure functional synaptic connectivity. Further development of this approach could result in greater functional integration of stem cell-derived grafts for the treatment of neural injuries and diseases affecting the central and peripheral nervous systems.
Publisher: Elsevier BV
Date: 09-2020
Publisher: American Vacuum Society
Date: 07-05-2008
DOI: 10.1116/1.2912097
Abstract: Tethered bilayer lipid membranes have been shown to be an excellent model system for biological membranes. Coupling of a membrane to a solid supports creates a stable system that is accessible for various surface analytical tools. Good electrical sealing properties also enable the use of the membranes in practical sensing applications. The authors have shown that tethered membranes have extended lifetimes up to several months. Air-stability of the bilayer can be achieved by coating the membrane with a hydrogel. The structure of a monolayer and its stability under applied dc potentials have been investigated by neutron scattering. © 2008 American Vacuum Society.
Publisher: American Chemical Society (ACS)
Date: 03-2019
DOI: 10.1021/ACS.BIOCONJCHEM.9B00015
Abstract: Upon contact with biological fluids, the surface of nanoparticles is surrounded by many types of proteins, forming a so-called "protein corona". The physicochemical properties of the nanoparticle/corona complex depend predominantly on the nature of the protein corona. An understanding of the structure of the corona and the resulting complex provides insight into the structure-activity relationship. Here, we structurally evaluate the soft and hard components of the protein corona, formed from polystyrene (PS) nanoplastics and human serum albumin (HSA). Using circular dichroism spectroscopy to elucidate the structure of HSA within the complex, we establish the effect of nanoparticle size and pH on the nature of the protein corona formed- whether hard or soft. Despite the weak interaction between PS and the HSA corona, small angle neutron scattering revealed the formation of a complex structure that enhanced the intermolecular interactions between HSA proteins, PS particles, and the HS/PSA complexes. Fractal formation occurred under conditions where the interaction between PS and HSA was strong, and increasing HSA concentrations suppressed the degree of aggregation. The size of the nanoparticles directly influenced the nature of the protein corona, with larger particles favoring the formation of a soft corona, due to the decreased PS-HSA attraction.
Publisher: Royal Society of Chemistry (RSC)
Date: 2015
DOI: 10.1039/C5RA22744E
Abstract: The linear and nonlinear rheology of physically-crosslinked-gelatin gel-multiwalled carbon nanotube (MWNT), chemically-crosslinked-gelatin gel-MWNT, and chemically–physically-crosslinked-gelatin gel-MWNT composites, are investigated.
Publisher: Wiley
Date: 18-08-2016
DOI: 10.1002/BIP.22917
Abstract: For the optimal use of β-lactoglobulin nanofibrils as a raw material in biological composites an in-depth knowledge of their interactions with other constituents is necessary. To understand the effect of electrostatic interactions on the morphology of resulting complexes, β-lactoglobulin nanofibrils were allowed to interact with pectins in which the amount of available negative charge was controlled by selecting their degree of methylesterification. In this study, citrus pectins having different degrees of methylesterification (∼48, 67, 86, and 97%) were selected and interacted with nanofibrils at pH 2 and pH 3, where they possess a net positive charge. Electrostatic complexes formed between β-lactoglobulin nanofibrils and all pectin types, except for the s le having a degree of methylesterification of 97%. The morphology of these complexes, however, differed significantly with the degree of methylesterification of the pectin, its concentration, and the pH of the medium, revealing that distinct desired biological architectures can be attained relatively easily through manipulating the electrostatic interactions. Interestingly, the pectin with a degree of methylesterification of 86% was found to crosslink the β-lactoglobulin nanofibrils into ordered 'nanotapes'.
Publisher: Inderscience Publishers
Date: 2017
Publisher: Elsevier BV
Date: 10-2015
Publisher: Royal Society of Chemistry (RSC)
Date: 2009
DOI: 10.1039/B822411K
Publisher: Elsevier BV
Date: 02-2021
Publisher: American Chemical Society (ACS)
Date: 13-10-2017
Publisher: American Chemical Society (ACS)
Date: 07-2018
DOI: 10.1021/ACS.LANGMUIR.8B00434
Abstract: This work systematically explores the biomineralization of calcium phosphate (CaP) and carbonate (CaCO
Publisher: Elsevier BV
Date: 04-2018
Publisher: American Chemical Society (ACS)
Date: 07-06-2017
Abstract: Understanding the interaction of adsorbed or covalently immobilized proteins with solid substrates at the molecular level guides the successful design of functionalized surfaces used in biomedical applications. In this report, neutron reflectometry (NR) was used to characterize the structure of surface-attached antimicrobial protein films, with antimicrobial activity assessed using an adaption of the Japanese Industrial Standard Test JIS Z 2801. NR allowed parameters influencing bioactivity to be measured at nanometer resolution and for conclusions about structural characteristics relating to bioactivity to be drawn. Hydramacin-1 (HM-1) and lysozyme were covalently attached to poly(methyl methacrylate) (PMMA) and 3-aminopropyltriethoxysilane (APTES) films in the presence and absence of a four-unit poly(ethylene glycol) PEG-based spacer and measured using NR, followed by antimicrobial assays. APTES-PEG-protein films were structurally unique, with a layer of 80% water directly beneath the protein layer, and were the only films that displayed antimicrobial activity against Escherichia coli and Bacillus subtilis. The hydration content of these films combined with the subtle difference in the PEG layer thickness of APTES versus PMMA films played a role in defining antimicrobial activity of the prepared surface coatings.
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C8SM00777B
Abstract: We investigate the effect of side chain length on the chain shape and thin film behaviour of conjugated graft copolymers.
Publisher: American Vacuum Society
Date: 07-2021
DOI: 10.1116/6.0001124
Abstract: Plastic waste is ubiquitously spread across the world and its smaller analogs-microplastics and nanoplastics-raise particular health concerns. While biological impacts of microplastics and nanoplastics have been actively studied, the chemical and biological bases for the adverse effects are sought after. This work explores contributory factors by combining results from in vitro and model mammalian membrane experimentation to assess the outcome of cell/nanoplastic interactions in molecular detail, inspecting the in idual contribution of nanoplastics and different types of protein coronae. The in vitro study showed mild cytotoxicity and cellular uptake of polystyrene (PS) nanoplastics, with no clear trend based on nanoplastic size (20 and 200 nm) or surface charge. In contrast, a nanoplastic size-dependency on bilayer disruption was observed in the model system. This suggests that membrane disruption resulting from direct interaction with PS nanoplastics has little correlation with cytotoxicity. Furthermore, the level of bilayer disruption was found to be limited to the hydrophilic headgroup, indicating that transmembrane diffusion was an unlikely pathway for cellular uptake-endocytosis is the viable mechanism. In rare cases, small PS nanoplastics (20 nm) were found in the vicinity of chromosomes without a nuclear membrane surrounding them however, this was not observed for larger PS nanoplastics (200 nm). We hypothesize that the nanoplastics can interact with chromosomes prior to nuclear membrane formation. Overall, precoating PS particles with protein coronae reduced the cytotoxicity, irrespective of the corona type. When comparing the two types, the extent of reduction was more apparent with soft than hard corona.
No related grants have been discovered for Duncan McGillivray.