ORCID Profile
0000-0003-1115-7524
Current Organisation
Monash University
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Chemical and thermal processes in energy and combustion | Chemical engineering | Carbon capture engineering (excl. sequestration) | Waste management reduction reuse and recycling | Bioprocessing bioproduction and bioproducts | Chemical engineering design
Publisher: Wiley
Date: 03-03-2023
Abstract: Coatings of anisotropic nanoparticles such as cellulose nanocrystals (CNCs) can provide tuneable physicochemical surface properties to a substrate such as modifying wettability. These coatings are often formed using dip coating, with CNCs enriched at the air–water interface transferred to a substrate as a monolayer. This process is commonly facilitated by surfactants, which can remain present in the final product, affecting coating properties. In this work, an “additive free” method for creating CNC coatings by exploiting electrostatic interactions within the pH window between pH 2–4 is demonstrated. Within this pH window, the air–water interface is positively charged and CNCs are negatively charged, with surface pressure tensiometry, X‐ray reflectivity, and Brewster angle microscopy indicating that CNCs are driven to the air–water interface. The optimal condition for monolayer coverage was pH 3 at pH 2 charge screening causes localized flocculation at the air–water interface, and at pH 4 interparticle repulsion leads to incomplete, patchy coverage. These findings successfully translate to dip coated CNC monolayers as characterized by atomic force microscopy, showing that the manipulation of pH can facilitate the surfactant‐free dip coating of CNCs, with advantages over the surfactants that are more typically used.
Publisher: American Chemical Society (ACS)
Date: 29-10-2015
DOI: 10.1021/ACS.LANGMUIR.5B03256
Abstract: Lipidic bicontinuous cubic mesophases with encapsulated hiphilic proteins are widely used in a range of biological and biomedical applications, including in meso crystallization, as drug delivery vehicles for therapeutic proteins, and as biosensors and biofuel cells. However, the effect of hiphilic protein encapsulation on the cubic phase nanostructure is not well-understood. In this study, we illustrate the effect of incorporating the bacterial hiphilic membrane protein Ag43, and its in idual hydrophobic β(43) and hydrophilic α(43) domains, in bicontinuous cubic mesophases. For the monoolein, monoalmitolein, and phytantriol cubic phases with and without 8% w/w cholesterol, the effect of the full length hiphilic protein Ag43 on the cubic phase nanostructure was more significant than the sum of the in idual hydrophobic β(43) and hydrophilic α(43) domains. Several factors were found to potentially influence the impact of the hydrophobic β(43) domain on the cubic phase internal nanostructure. These include the size of the hydrophobic β(43) domain relative to the thickness of the lipid bilayer, as well as its charge and diameter. The size of the hydrophilic α(43) domain relative to the water channel radius of the cubic mesophase was also found to be important. The secondary structure of the Ag43 proteins was affected by the hydrophobic thickness and physicochemical properties of the lipid bilayer and the water channel diameter of the cubic phase. Such structural changes may be small but could potentially affect membrane protein function.
Publisher: Royal Society of Chemistry (RSC)
Date: 2021
DOI: 10.1039/D1FD90068D
Publisher: American Chemical Society (ACS)
Date: 12-06-2019
DOI: 10.1021/ACS.LANGMUIR.9B00647
Abstract: For evolving biological and biomedical applications of hybrid protein?lipid materials, understanding the behavior of the protein within the lipid mesophase is crucial. After more than two decades since the invention of the in meso crystallization method, a protein-eye view of its mechanism is still lacking. Numerous structural studies have suggested that integral membrane proteins preferentially partition at localized flat points on the bilayer surface of the cubic phase with crystal growth occurring from a local fluid lamellar L
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/C9FO01175G
Abstract: Controlled drying preserves African leafy vegetables and fight micronutrient deficiency during droughts. The palisade parenchyma cell length determines their rehydration capacity and starch granules the texture upon cooking.
Publisher: Wiley
Date: 10-01-2020
Publisher: American Chemical Society (ACS)
Date: 29-06-2016
DOI: 10.1021/ACS.LANGMUIR.6B01800
Abstract: A fundamental understanding of the effect of hiphilic protein encapsulation on the nanostructure of the bicontinuous cubic phase is crucial to progressing biomedical and biological applications of these hybrid protein-lipid materials, including as drug delivery vehicles, as biosensors, biofuel cells and for in meso crystallization. The relationship between the lipid nanomaterial and the encapsulated protein, however, remains poorly understood. In this study, we investigated the effect of incorporating the five transmembrane and lipo-proteins which make up the β-barrel assembly machinery from Gram-negative bacteria within a series of bicontinuous cubic phases. The transmembrane β-barrel BamA caused an increase in lattice parameter of the cubic phase upon encapsulation. By contrast, the mainly hydrophilic lipo-proteins BamB-E caused the cubic phase lattice parameters to decrease, despite their large size relative to the diameter of the cubic phase water channels. Analysis of the primary amino acid sequence was used to rationalize this effect, based on specific interactions between aromatic amino acids within the proteins and the polar-apolar interface. Other factors that were found to have an effect were lateral bilayer pressure and rigidity within the lipid bilayer, water channel diameter, and size and structure of the lipo-proteins. The data presented suggest that hydrophilic bioactive molecules can be selectively encapsulated within the cubic phase by using a lipid anchor or aromatic amino acids, for drug delivery or biosensing applications.
Publisher: Elsevier BV
Date: 08-2023
Publisher: The Royal Society
Date: 28-07-2016
Abstract: The proposed mechanism for in meso crystallization of transmembrane proteins suggests that a protein or peptide is initially uniformly dispersed in the lipid self-assembly cubic phase but that crystals grow from a local lamellar phase, which acts as a conduit between the crystal and the bulk cubic phase. However, there is very limited experimental evidence for this theory. We have developed protocols to investigate the lipid mesophase microenvironment during crystal growth using standard procedures readily available in crystallography laboratories. This technique was used to characterize the microenvironment during crystal growth of the DAP12-TM peptide using synchrotron small angle X-ray scattering (SAXS) with a micro-sized X-ray beam. Crystal growth was found to occur from the gyroid cubic mesophase. For one in four crystals, a highly oriented local lamellar phase was observed, providing supporting evidence for the proposed mechanism for in meso crystallization. A new observation of this study was that we can differentiate diffraction peaks from crystals grown in meso , from peaks originating from the surrounding lipid matrix, potentially opening up the possibility of high-throughput SAXS analysis of in meso grown crystals. This article is part of the themed issue ‘Soft interfacial materials: from fundamentals to formulation’.
Publisher: Public Library of Science (PLoS)
Date: 06-02-2017
Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C6SM02487D
Abstract: Activity of large hydrophilic domain hiphilic enzymes in lipid self-assembly materials is crucial for drug delivery, crystallization and biosensing applications.
Publisher: Elsevier BV
Date: 05-2019
Publisher: American Chemical Society (ACS)
Date: 14-07-2016
DOI: 10.1021/ACS.JPCLETT.6B01173
Abstract: An understanding of the location of peptides, proteins, and other biomolecules within the bicontinuous cubic phase is crucial for understanding and evolving biological and biomedical applications of these hybrid biomolecule-lipid materials, including during in meso crystallization and drug delivery. While theoretical modeling has indicated that proteins and additive lipids might phase separate locally and adopt a preferred location in the cubic phase, this has never been experimentally confirmed. We have demonstrated that perfectly contrast-matched cubic phases in D2O can be studied using small-angle neutron scattering by mixing fully deuterated and hydrogenated lipid at an appropriate ratio. The model transmembrane peptide WALP21 showed no preferential location in the membrane of the diamond cubic phase of phytanoyl monoethanolamide and was not incorporated in the gyroid cubic phase. While deuteration had a small effect on the phase behavior of the cubic phase forming lipids, the changes did not significantly affect our results.
Publisher: Royal Society of Chemistry (RSC)
Date: 2021
DOI: 10.1039/D1FD90066H
Publisher: Springer Science and Business Media LLC
Date: 18-03-2021
Publisher: American Chemical Society (ACS)
Date: 30-06-2016
DOI: 10.1021/ACS.LANGMUIR.6B01058
Abstract: Nanostructured bicontinuous lipidic cubic phases are used for the encapsulation of proteins in a range of applications such as in meso crystallization of transmembrane proteins and as drug delivery vehicles. The retention of the nanoscale order of the cubic phases subsequent to protein incorporation, as well as retention of the protein structure and function, is essential for all of these applications. Herein synthetic peptides (WALP21, WALPS53, and WALPS73) with a common α-helical hydrophobic domain, but varying hydrophilic loop size, were designed to systematically examine the effect of peptide structure and charge on bicontinuous cubic phases. The effect of the cubic phases on the secondary structure of the peptides was also investigated. The incorporation of the WALP peptides in cubic phases formed by a range of lipids showed that hydrophobic mismatch of the peptides with the lipid bilayers, the hydrophilic domain size, and peptide charge were all significant factors determining the response of the lipid nanomaterial to protein insertion. As charge repulsion had the most significant effect on the phase transitions observed, we suggest that buffer pH and salt concentration must be carefully considered to ensure cubic mesophase retention. Importantly, the WALP peptides were found to have a different conformation depending on the local lipid environment. Such structural changes could potentially affect membrane protein function, which is crucial for both current and prospective applications.
Publisher: American Chemical Society (ACS)
Date: 20-04-2023
Publisher: Elsevier BV
Date: 10-2021
Publisher: Royal Society of Chemistry (RSC)
Date: 2023
DOI: 10.1039/D3BM00477E
Abstract: The polymer–lipid nanodisc forming ability of a novel class of hipathic copolymer comprised of an alternating sequence was established. Selective membrane disruption was shown to be tuneable in relation to polymer hydrophobicity.
Publisher: Springer Science and Business Media LLC
Date: 02-2013
DOI: 10.1039/C2PP25170A
Abstract: In the standard nanosecond laser photolysis method for kinetic studies, a Q-switched laser generates transient species, and absorption spectrophotometry provides a measure of their concentrations. The s le is placed between the monitoring source (a pulsed xenon arc or a flash l ) and a monochromator, and a photomultiplier tube (PMT) is used for measuring the intensity of the light leaving the exit slit of the monochromator. With this (single-beam) arrangement, the laser-induced change in the absorbance of the s le, ΔA, can be calculated only if the intensity of the monitoring beam remains constant during the time interval of interest. When this condition is not fulfilled, a second measurement of the PMT output is made after blocking the path of the laser beam, but shot-to-shot variations in the output of the monitoring source vitiate the analysis when ΔA is small. To overcome this problem, double-beam versions were developed in the last century, but the single-beam version still enjoys greater popularity. With a view to making the double-beam method easily implementable, some simple modifications are introduced, which permit the conversion of an existing laser kinetic spectrometer into a double-beam variant (with one or two monochromators).
Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C6CS00663A
Abstract: Engineering guidelines for an increased control over properties of self-assembly materials using multi-component systems is crucial for their applications.
Publisher: Elsevier BV
Date: 05-2015
Publisher: American Chemical Society (ACS)
Date: 26-02-2014
DOI: 10.1021/CG4018954
Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C6SM02487D
Abstract: Activity of large hydrophilic domain hiphilic enzymes in lipid self-assembly materials is crucial for drug delivery, crystallization and biosensing applications.
Publisher: Elsevier BV
Date: 10-2023
Publisher: Frontiers Media SA
Date: 09-02-2021
DOI: 10.3389/FCHEM.2020.619470
Abstract: This perspective describes advances in determining membrane protein structures in lipid bilayers using small-angle neutron scattering (SANS). Differentially labeled detergents with a homogeneous scattering length density facilitate contrast matching of detergent micelles this has previously been used successfully to obtain the structures of membrane proteins. However, detergent micelles do not mimic the lipid bilayer environment of the cell membrane in vivo . Deuterated vesicles can be used to obtain the radius of gyration of membrane proteins, but protein-protein interference effects within the vesicles severely limits this method such that the protein structure cannot be modeled. We show herein that different membrane protein conformations can be distinguished within the lipid bilayer of the bicontinuous cubic phase using contrast-matching. Time-resolved studies performed using SANS illustrate the complex phase behavior in lyotropic liquid crystalline systems and emphasize the importance of this development. We believe that studying membrane protein structures and phase behavior in contrast-matched lipid bilayers will advance both biological and pharmaceutical applications of membrane-associated proteins, biosensors and food science.
Start Date: 01-2025
End Date: 01-2029
Amount: $4,955,854.00
Funder: Australian Research Council
View Funded ActivityStart Date: 08-2023
End Date: 08-2029
Amount: $5,000,000.00
Funder: Australian Research Council
View Funded Activity