ANSTO :: Browsing by Author "Garvey, CJ"

Browsing by Author "Garvey, CJ"

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Behaviour of single transmembrane peptides during in meso crystallization from the contrast-matched lipidic cubic phase of monoolein
(Australian Institute of Nuclear Science and Engineering (AINSE), 2018-11-19) van't Hag, L; de Campo, L; Tran, N; Sokolova, AV; Trenker, R; Call, M; Garvey, CJ; Leung., A; Darwish, TA; Krause-Heuer, AM; Knott, RB; Meikle, T; Gras, S; Drummond, CJ; Mezzenga, R; Conn, C
In meso membrane protein crystallization within a lipidic mesophase has revolutionized the structural biology of integral membrane proteins (IMPs). High-resolution structures of these proteins are crucial to understanding fundamental cellular processes at a molecular level, and can lead to new and improved treatments for a wide range of diseases via rational drug design. However, overall success rates of the promising in meso crystallization technique remain low because of a fundamental lack of understanding about factors that promote crystal growth. In particular, to date, two decades from invention of the method, the protein-eye-view of the in meso crystallization mechanism had not been solved. We have investigated this for the first time using small-angle neutron scattering (SANS). Contrast-matching between the scattering of the lipid membrane formed by MO and the aqueous solution was used to isolate and track the scattering of single-transmembrane peptides during the growth of protein crystals in meso. No peptide enrichment was observed at the flat points of the diamond cubic QIID phase of MO in contrast to suggestions in several modeling studies. During in meso crystallization of the DAP12 peptide a decrease in form factor and a transient fluid lamellar Lα phase could be observed providing direct evidence for the proposed crystallization mechanism. Synthesis of fully deuterated MO was required for this purpose and scattering of this new material in various solvents and under a range of conditions will be described, specifically regarding the effect of the relative scattering length densities (SLD) of the headgroup, acyl chain and solvent, which can advance the use of neutron scattering with other self-assembly materials. © The Authors.
Biopolymer deuteration for neutron scattering and other isotope-sensitive techniques
(Elsevier, 2015) Russell, RA; Garvey, CJ; Darwish, TA; Foster, LJR; Holden, PJ
The use of microbial biosynthesis to produced deuterated recombinant proteins is a well-established practice in investigations of the relationship between molecular structure and function using neutron scattering and nuclear magnetic resonance spectroscopy. However, there have been few reports of using microbial synthetic capacity to produce labeled native biopolymers. Here, we describe methods for the production of deuterated polyhydroxyalkanoate biopolyesters in bacteria, the polysaccharide chitosan in the yeast Pichia pastoris, and cellulose in the bacterium Gluconacetobacter xylinus. The resulting molecules offer not only multiple options in creating structural contrast in polymer blends and composites in structural studies but also insight into the biosynthetic pathways themselves. © 2015 Elsevier Inc.
Cellulose dissolution in ionic liquid: ion binding revealed by neutron scattering
(ACS Publications, 2018-09-20) Raghuwanshi, VS; Cohen, Y; Garnier, GFG; Garvey, CJ; Russell, RA; Darwish, TA; Garnier, G
Dissolution of cellulose in 1-ethyl-3-methylimidazolium acetate (EMIMAc) ionic liquid (IL) was investigated by small-angle neutron scattering (SANS) with contrast variation. Cellulose and EMIMAc of different deuteration levels provide sufficient contrast in revealing the cellulose dissolution processes. Two experiments were performed: hydrogenated microcrystalline cellulose (MCC) was dissolved in deuterated IL (IL-D14), and deuterated bacterial cellulose (DBC) was dissolved in hydrogenated IL (IL-H14). Contrary to the expectation of high contrast between MCC and IL-D14, a dramatic reduction of the measured intensity (scattering cross section) was observed, about 1/3 of the value predicted based on the scattering length density (SLD) difference. This is attributed to the tight binding of acetate ions to the cellulose chains, which reduces the SLD difference. Measurements using small-angle X-ray scattering (SAXS) corroborate this effect by indicating increased contrast due to ion adsorption resulting in enhanced SLD difference. The experiments performed with DBC dissolution in IL-H14 suggest the presence of fractal aggregates of the dissolved cellulose, indicating lower solubility compared to the MCC. Contrast variation SANS measurements highlight tight ion binding of at least one acetate ion per anhydroglucose unit (AGU). EMIMAc is a successful cellulose solvent, as in addition to disrupting intermolecular hydrogen bonding, it imparts effective charge to the cellulose chains hindering their agglomeration in solution. © 2018 American Chemical Society
Challenges of kinetic measurements with a Bonse-Hart neutron diffractometer
(International Conference on Neutron Scattering, 2017-07-12) Garvey, CJ; de Campo, L; Rehm, C; Muzny, CD; Hanley, HJM
Here we report on kinetic studies of the structural effects of applied shear on the gelation of silica using the Bonse-Hart type double crystal diffractometer (USANS) Kookaburra (ANSTO, Lucas Heights Australia). This instrument is able to cover a range of scattering vectors, 2.8 x 10-5 Å-1 < q < 4x 10-2 Å-1. The gelation process may be viewed structurally as the aggregation of sol particles into larger fractal aggregates, which then form a percolative network (final gel). In previous SANS work, it was shown that shear interrupted the formation of the network, inducing a new, shear dependent structure where there are structural changes on the micron length scale. Here we use USANS to understand the structural pathway that the gel follows to the steady shear state. USANS measurements are made point by point with each rotation step of the analyzer crystal (rocking curve), with counting statistics aimed at resolving a signal above the background. To gather a comprehensive rocking curve, a single measurement will take of the order of hours, putting the ability to cover interesting kinetics beyond the realm of an ordinary beamtime allocation. Here, USANS measurements were made on the gelling system, where each measurement consists of a restricted number of points in the rocking curve, with points selected according to their ability to characterize the intermediate structure.
Changes in microfibril angle in cyclically deformed dry coir fibers studied by in-situ synchrotron x-ray diffraction
(Springer, 2008-01) Martinschitz, KJ; Boesecke, P; Garvey, CJ; Gindl, W; Keckes, J
Dry coir fibers are characterized by wideangle X-ray scattering coupled with tensile tests. The fibers exhibit elastic and plastic behavior with the yield point at a strain of about 2%. In-situ experiments document that the cyclic loading and unloading beyond the yield point does not reduce the stiffness of the fibres, since they recover their initial stiffness by every increase of the strain. The diffraction data show that the microfibril angle (MFA) of cellulose fibrils in the coir fibre cells is inversely proportional to the magnitude of the applied strain. In average, the relatively high MFA of about 45 degrees in the unstrained state decreases linearly upon straining until the fibers break at about 35% strain. When the strain is released during the tensile experiment the MFA tends to recover its original magnitude. No significant differences in the dependence of MFA on strain are detected in elastic and plastic regions, respectively. The results demonstrate that the tissue with helical architecture does not have to be saturated with water in order to exhibit the effect of the recovery of the mechanical function when cyclically loaded. This indicates differences in the architecture of the coir cell wall in comparison with that of compression wood with high MFA whereby similar phenomena were observed in the wet state. © 2008, Springer.
Characterization of porosity in sulfide ore minerals: a USANS/SANS study
(GeoScience World, 2014-11-18) Xia, F; Zhao, J; Etschmann, BE; Brugger, J; Garvey, CJ; Rehm, C; Lemmel, H; Ilavsky, J; Han, YS; Pring, A
Porosity plays a key role in the formation and alteration of sulfide ore minerals, yet our knowledge of the nature and formation of the residual pores is very limited. Herein, we report the application of ultra-small-angle neutron scattering and small-angle neutron scattering (USANS/SANS) to assess the porosity in five natural sulfide minerals (violarite, marcasite, pyrite, chalcopyrite, and bornite) possibly formed by hydrothermal mineral replacement reactions and two synthetic sulfide minerals (violarite and marcasite) prepared experimentally by mimicking natural hydrothermal conditions. USANS/SANS data showed very different pore size distributions for these minerals. Natural violarite and marcasite tend to possess less pores in the small size range (<100 nm) compared with their synthetic counterparts. This phenomenon is consistent with a higher degree of pore healing or diagenetic compaction experienced by the natural violarite and marcasite. Surprisingly, nanometer-sized (<20 nm) pores were revealed for a natural pyrite cube from La Rioga, Spain, and the sample has a pore volume fraction of ~7.7%. Both chalcopyrite and bornite from the massive sulfide assemblage of the Olympic Dam deposit in Roxby Downs, South Australia, were found to be porous with a similar pore volume fraction (~15%), but chalcopyrite tends to have a higher proportion of nanometer-size pores centered at ~4 nm while bornite tends to have a broader pore size distribution. The specific surface area is generally low for these minerals ranging from 0.94 to 6.28 m2/g, and the surfaces are generally rough as surface fractal behavior was observed for all these minerals. This investigation has demonstrated that USANS/SANS is a very useful tool for analyzing porosity in ore minerals. We believe that with this quantified porosity information a deeper understanding of the complex fluid flow behavior within the porous minerals can be expected. © 2014, Mineralogical Society of America.
Complex structured polymers in extensional flow – rheology and small-angle neutron scattering
(International Conference on Neutron Scattering, 2017-07-12) Mortensen, K; Kirkensgaard, JJK; Borger, A; Hassager, O; Almdal, K; Huang, Q; Dorokhin, A; Garvey, CJ
Small-Angle Neutron Scattering are used to investigate stretched macromolecular fluid filaments to show how the extensional properties are related to the molecular architecture and properties. We have combined structural and rheological studies of a series of model polymers with different composition and architectures. The project entails synthesizing model polymer systems of specific architecture, subjecting these materials to controlled extensional flows and to measure the molecular deformation under controlled flow situation bySANS. We have targeted different systems: a ”simple\" sample of homogeneous high-molar mass polymers, where only the central part of a fraction of the polymers were D-labelled with the aim to highlight the polymer deformation and avoid influence of fast relaxation near the polymer ends [1]. Another example is a bimodal mixture of linear polymer chains with respectively high and low molar mass [2], and we have studied samples with more complex geometry, including 3-arm star architecture. The linear chains show typically 2D-SANS pattern with Lozenge shaped contour. The 3-arm star polymers show novel, unexpected correlations perpendicular to the flow axis. The structure and rheology are measured both as a function of strain flow velocity, final Hencky strain ratio and during the relaxation after cessation of extensional flow.
Determination of Na+ binding parameters by relaxation analysis of selected 23Na NMR coherences: RNA, BSA and SDS
(John Wiley & Sons, 2005-03) Torres, AM; Philp, DJ; Kemp-Harper, R; Garvey, CJ; Kuchel, PW
Nuclear magnetic resonance provides several unique means of investigating the interactions between different inorganic ions and various macromolecules. 23Na is a quadrupolar nucleus, meaning that relaxation analysis of the various coherences allows the measurement of its binding to biological macromolecules. In this study, we analyzed the quadrupolar relaxation of 23Na+ longitudinal magnetization and single- and triple-quantum coherences in aqueous systems containing RNA, bovine serum albumin and sodium dodecyl sulfate micelles. The effectiveness of the James-Noggle method for determining binding constants was evaluated in these systems, and also the applicability of various 23Na coherences in providing information on the extent and affinity of binding to the three different classes of biomolecules. © 2004, John Wiley & Sons Ltd.
Drug-induced morphology transition of self-assembled glycopolymers: insight into the drug-polymer interaction
(Australian Institute of Nuclear Science and Engineering (AINSE), 2018-11-18) Cao, C; Zhao, JC; Chen, F; Lu, MG; Khine, YY; Macmillanc, A; Garvey, CJ; Stenzel. M
It is often assumed that a hydrophobic drug will be entrapped in the hydrophobic environment of a micelle. Little attention is usually drawn to the actual location of the drug and the effect of the drug on properties. In this publication, we show how the chosen drug curcumin is not only unexpectedly located in the shell of the micelle, but that the accumulation in the hydrophilic block can lead to changes in morphology during self-assembly. A block copolymer poly(1-O-methacryloyl -β-D-fructopyranose)-b-poly(methyl methacrylate), Poly(1-O-MAFru)36-b-PMMA192, was loaded with different amounts of curcumin. The resulting self-assembled nanoparticles were analyzed using TEM, SAXS, and SANS. Initial microscopy evidence revealed that the presence of the drug induces morphology changes from cylindrical micelles (no drug) to polymersomes, which decreased in size with increasing amount of drug (Figure 1). SAXS and SANS analysis, supported by fluorescence studies, revealed that the drug is interacting with the glycopolymer block. The drug did not only influence the shape of the drug carrier, but also the level of cof the shell. Increasing the amount of drug dehydrated the nanoparticle shell, which coincided with a lower nanoparticle uptake by MCF-7 breast cancer cells and non-cancerous Raw-264.7 cells. As a result, we showed that the drug can influence the behaviour of the fluorescence in terms of shape and shell hydration, which could influence the performance in a biological setting (Figure 1). Although the depicted scenario may not apply to every drug carrier, it is worth evaluation if the drug will interfere in unexpected ways, for example, when the drug locates on the surface and affects the internal structure of the nanocarrier. © The Authors.
Effects of sugars on lipid bilayers during dehydration - SAXS/WAXS measurements and quantitative model
(American Chemical Society, 2009-02-26) Lenné, T; Garvey, CJ; Koster, KL; Bryant, G
We present an X-ray scattering study of the effects of dehydration on the bilayer and chain-chain repeat spacings of dipalmitoylphosphatidylcholine bilayers in the presence of sugars. The presence of sugars has no effect on the average spacing between the phospholipid chains in either the fluid or gel phase. Using this finding, we establish that for low sugar concentrations only a small amount of sugar exclusion occurs. Under these conditions, the effects of sugars on the membrane transition temperatures can be explained quantitatively by the reduction in hydration repulsion between bilayers due to the presence of the sugars. Specific bonding of sugars to lipid headgroups is not required to explain this effect. © 2009, American Chemical Society
Fluorinated lamellar phases: structural characterisation and use as templates for highly ordered silica materials
(Royal Society of Chemistry, 2014-05-13) Pottage, MJ; Tiara, K; Grillo, I; Garvey, CJ; Stickland, AD; Tabor, RF
Highly ordered silica was synthesised by using a lamellar phase comprising the anionic fluorinated surfactant sodium perfluorooctanoate and the partially-fluorinated co-surfactant/oil 1H,1H,2H,2H-perfluorooctan-1-ol in water. The phase behaviour of this system was thoroughly analysed, and it was found that even low levels of the alcohol (<0.5 mol%) were sufficient to induce a phase change from normal micelles to a lamellar phase, rationalised as a result of geometric and electrostatic effects. The properties of these phases were compared to their hydrocarbon analogues, demonstrating the unique and valuable properties exhibited by fluorocarbons, directly related with the observed nanostructure. Small-angle neutron scattering was used to analyse the internal structure of the systems, providing information on the inter-lamellar spacing, bilayer thickness and membrane elasticity. The potential for these phases to act as shear-thinning lubricants was assessed using oscillatory rheology, obtaining shear-dependent viscosity along with storage and loss moduli.© 2014, The Royal Society of Chemistry.
A fundamental study on photo-oxidative degradation of linear low density polyethylene films at embrittlement
(Elsevier, 2012-05-25) Hsu, YC; Weir, MP; Truss, RW; Garvey, CJ; Nicholson, TM; Halley, PJ
Film embrittlement criteria were determined for photo-oxidative degradation of linear low density polyethylene (LLDPE) films by using a range of characterisation techniques: tensile, high-temperature GPC, MAS-NMR, FTIR-ATR, WAXS and SAXS. The key embrittlement criteria was the loss of 95% elongation at break and the reduction in interlamellar distance, reduced down to approximately 30–50 Å, as a result of recrystallisation of mobile short chain fragments produced from chain scission reaction. Interlamellar thinning correlated well with the changes in double yield points seen in the tensile data, where the absence of the second yield point signified that the tie molecules at the lamellar interface underwent chain scission and could no longer transfer the tensile stress to reach c-axis slip of the lamellar crystals. This was also supported by a reduction in amorphous–lamellar interfacial width with ageing time, extracted from SAXS data using the linear correlation function. Crown Copyright (C) 2012 Published by Elsevier Ltd. All rights reserved.
H2O/D2O contrast variation for ultra-small-angle neutron scattering to minimize multiple scattering effects of colloidal particle suspensions
(MDPI, 2018-09-07) Otsuki, A; de Campo, L; Garvey, CJ; Rehm, C
This study investigated the use of solvent contrast (H2O/D2O ratio) as a means to optimize the ultra-small-angle neutron scattering (USANS) signal. By optimizing the signal, it was possible to reduce the undesirable effects of coherent multiple scattering while still maintaining a measurable scattered intensity. This result will further enable the use of USANS as a probe of the interactions between colloidal particles and their structures within concentrated suspensions as well as particle dispersion/aggregation. As a model system, we prepared silica colloidal particle suspensions at different solid concentrations. USANS curves were measured using the classical Bonse–Hart double crystal diffractometer while varying the scattering length density of the aqueous phase, thus varying the contrast to the silica particles. As a means of assessing the impact of multiple scattering effects on different q-values, we analyzed the scattered intensity at different contrasts at three different q values. The data were then used to determine the match point of the silica particle suspensions from the expected square root dependence of the scattered intensity with solvent composition, to analyze any differences associated with the solid concentration change, and to determine the optimum H2O/D2O ratio in terms of high transmission (TSAS > 80%) and high enough scattering intensity associated with the contrast of the system. Through this investigation series, we confirmed that adjusting the contrast of the solvent (H2O/D2O) is a good methodology to reduce multiple scattering while maintaining a strong enough scattering signal from a concentrated suspension of silica particles for both USANS and rheometric USANS (rheo-USANS) experiments.© The Authors - This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited
Hydration of paper studied with solid-state magnetisation-exchange H-1 NMR spectroscopy
(Walter de Gruyter, 2006-07) Garvey, CJ; Parker, IH; Simon, GP; Whittaker, AK
The wide-line H-1 nuclear magnetic resonance (NMR) spectrum of paper in equilibrium with ambient humidity consists of super-imposed relatively broad and narrow lines. The narrower line is of the order of 2 kHz wide at half the maximum height, while the broader line is of the order of 40 kHz in width at half height. On the basis of these line widths, the narrow line is assigned to water sorbed to the paper, and the broad line to the polymeric constituents of the paper. It was not possible to distinguish between the various polymeric components of paper contributing to the H-1 NMR spectra. A modified Goldman-Shen pulse sequence was used to generate a spatial magnetisation gradient between the polymer and water phases. The exchange of magnetisation between protons associated with water and those associated with the macromolecules in paper was observed. The exchange of magnetisation is discussed within a heat transfer model for homonuclear dipolar coupling, with exchange being characterised by a spin-diffusion coefficient. Consideration of the magnitude of the initial rate of the exchange process and estimates of the spin-spin relaxation times based on H-1 line widths indicate that some water must exist in a sufficiently immobile state as to allow homonuclear dipolar interactions between adjacent polymer and water protons. Thus, water sorbed onto paper must exist in at least two states in mass exchange with each other. This observation allows certain conclusions to be drawn about the ratio of free/bound water as a function of moisture content and the dispersal of water within the polymer matrix. © 2006, Walter de Gruyter
In vivo deuteration of a native bacterial biopolymer for structural elucidation using SANS
(Elsevier, 2004-07-15) Holden, PJ; Russell, RA; Stone, DJM; Garvey, CJ; Foster, LJR
In order to facilitate future structural studies, biodeuteration of bacterial polyhydroxyalkanoates (PHAs) was investigated. We report here the in vivo deuteration of poly 3-hydroxyoctanoate (PHO) produced by its native host, the bacterium Pseudomonas oleovorans. Bacterial biomass was produced in bioreactor studies by growth on hydrogenated substrates and PHO was subsequently produced intracellularly (10–20% w/w) during batch fed growth on deuterated octanoic acid under oxygen limitation. GC-MS analyses of the PHO demonstrated that 13 of the 15 hydrogen atoms had been replaced with deuterium (except in position 3), the remaining two hydrogen presumably being derived from water. A SANS contrast variation study was conducted on whole cells and the results indicate the potential to discriminate inclusion bodies formed from deuterated precursor from an otherwise hydrogenated background. © 2004, Elsevier Ltd.
In vivo deuteration strategies for neutron scattering analysis of bacterial polyhydroxyoctanoate
(Springer Nature, 2008-05-15) Russell, RA; Holden, PJ; Wilde, KL; Garvey, CJ; Hammerton, KM; Foster, LJR
The cultivation of microorganisms on deuterated substrates has allowed us to control deuterium incorporation into biopolymer systems which is important for characterisation using neutron scattering techniques. Bacterial polyhydroxyoctanoate (PHO) is a polyester formed within inclusions inside bacterial cells and was deuterated in vivo under various conditions to characterise the formation of these inclusions by neutron scattering. Manipulation of deuterated media during microbial growth and PHO production phases resulted in polymer with partial or complete substitution of hydrogen by deuterium, as shown by gas chromatography. Sequential feeding of hydrogenated and deuterated forms of the same precursor was used to demonstrate that neutron scattering analysis could be used to differentiate between chemically similar phases in these polymer inclusions. © 2008 Crown Copyright
Intrinsically disordered stress protein COR15A resides at the membrane surface during dehydration
(Biophysical Society, 2017-08-08) Bremer, A; Kent, B; Hauß, T; Thalhammer, A; Yepuri, NR; Darwish, TA; Garvey, CJ; Bryant, G; Hincha, DK
Plants from temperate climate zones are able to increase their freezing tolerance during exposure to low, above-zero temperatures in a process termed cold acclimation. During this process, several cold-regulated (COR) proteins are accumulated in the cells. One of them is COR15A, a small, intrinsically disordered protein that contributes to leaf freezing tolerance by stabilizing cellular membranes. The isolated protein folds into amphipathic α-helices in response to increased crowding conditions, such as high concentrations of glycerol. Although there is evidence for direct COR15A-membrane interactions, the orientation and depth of protein insertion were unknown. In addition, although folding due to high osmolyte concentrations had been established, the folding response of the protein under conditions of gradual dehydration had not been investigated. Here we show, using Fourier transform infrared spectroscopy, that COR15A starts to fold into α-helices already under mild dehydration conditions (97% relative humidity (RH), corresponding to freezing at −3°C) and that folding gradually increases with decreasing RH. Neutron diffraction experiments at 97 and 75% RH established that the presence of COR15A had no significant influence on the structure of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) membranes. However, using deuterated POPC we could clearly establish that COR15A interacts with the membranes and penetrates below the headgroup region into the upper part of the fatty acyl chain region. This localization is in agreement with our hypothesis that COR15A-membrane interaction is at least, in part, driven by a hydrophobic interaction between the lipids and the hydrophobic face of the amphipathic protein α-helix. © 2017 Biophysical Society - Open access
Inverse hexagonal - inverse ribbon - lamellar gel phase transition sequence in low hydration DOPC:DOPE phospholipid mixtures
(Elsevier, 2009-01) Kent, B; Garvey, CJ; Cookson, DJ; Bryant, G
The inverse hexagonal to inverse ribbon phase transition in a mixed phosphatidylcholine-phosphatidylethanolamine system at low hydration is studied using small and wide angle X-ray scattering. It is found that the structural parameters of the inverse hexagonal phase are independent of temperature. By contrast the length of each ribbon of the inverse ribbon phase increases continuously with decreasing temperature over a range of 50 C. At low temperatures the inverse ribbon phase is observed to have a transition to a gel lamellar phase, with no intermediate fluid lamellar phase. This phase transition is confirmed by differential scanning calorimetry. © 2008, Elsevier Ltd.
Investigation of the phase morphology of bacterial PHA inclusion bodies by contrast variation SANS
(Elsevier, 2006-11-15) Russell, RA; Holden, PJ; Garvey, CJ; Wilde, KL; Hammerton, KM; Foster, LJR
Under growth-limiting conditions, many bacteria are able to metabolise excess organic acids into polyhydroxyalkanoates (PHA) and store these polymers as intracellular inclusions until the return of favourable conditions. Various models have been proposed for the macromolecular organisation of the boundary layer Surrounding the polymer, and contrast-variation small-angle neutron scattering (SANS) was used to study its organisation. Inclusions formed by Pseudomonas oleovorans under hydrogenating conditions showed lowest scattering intensity at ca. 20% D2O. The inclusions consist of protein and membrane lipids in the boundary layer and polyhydroxyoctanoate (lipid) in the inclusion body. At 20% D2O the contributions of lipids were contrast matched with the solvent, indicating that lipids contributed the bulk of the scattering intensity observed at other D2O/H2O ratios. These results are inconsistent with a model of the boundary layer which proposed outer and inner layers of crystalline protein lattice sandwiching a membrane lipid membrane layer [E.S. Stuart, R.W. Lenz, R.C. Fuller, Can J Microbiol 41(Suppl 1) (1995) 84 93], and is more consistent with a model consisting of a lipid monolayer containing embedded proteins [U. Pieper-furst, M.H. Madkour, F. Mayer, A. Steinbuchel, J. Bacteriol. 176 (1994) 4328-4337.] By altering the H/D content of the precursors, we were able to collect SANS data from preparations of both deuterated and H/D copolymer inclusions, where initial PHA produced was hydrogenated followed by deuteration. Deuterated inclusions showed minimum intensity above 90% D2O/H2O whereas the sequentially produced copolymer (assumed to be in a core/shell arrangement) displayed minimum scattering some 20% lower, which is consistent with the increased hydrogenation of the boundary layer expected from its synthesis during supply of hydrogenated followed by deuterated precursors. © 2006, Elsevier Ltd
Kinetics of the lamellar gel-fluid transition in phosphatidylcholine membranes in the presence of sugars
(Elsevier, 2010-02) Lenné, T; Garvey, CJ; Koster, KL; Bryant, G
Phase diagrams are presented for dipalmitoylphosphatidylcholine (DPPC) in the presence of sugars (sucrose) over a wide range of relative humidities (RHs). The phase information presented here, determined by small angle X-ray scattering (SAXS), is shown to be consistent with previous results achieved by differential scanning calorimetry (DSC). Both techniques show a significant effect of sucrose concentration on the phase behaviour of this phospholipid bilayer. An experimental investigation into the effect of sugars on the kinetic behaviour of the gel to fluid transition is also presented showing that increasing the sugar content appears to slightly increase the rate at which the transition occurs. © 2010, Elsevier Ltd.

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