School of Chemistry - Research Publications
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ItemAromatic residues in the C-terminal helix of human apoC-I mediate phospholipid interactions and particle morphology(ELSEVIER, 2009-07-01)Human apolipoprotein C-I (apoC-I) is an exchangeable apolipoprotein that binds to lipoprotein particles in vivo. In this study, we employed a LC-MS/MS assay to demonstrate that residues 38-51 of apoC-I are significantly protected from proteolysis in the presence of 1,2-dimyristoyl-3-sn-glycero-phosphocholine (DMPC). This suggests that the key lipid-binding determinants of apoC-I are located in the C-terminal region, which includes F42 and F46. To test this, we generated site-directed mutants substituting F42 and F46 for glycine or alanine. In contrast to wild-type apoC-I (WT), which binds DMPC vesicles with an apparent Kd [Kd(app)] of 0.89 microM, apoC-I(F42A) and apoC-I(F46A) possess 2-fold weaker affinities for DMPC with Kd(app) of 1.52 microM and 1.58 microM, respectively. However, apoC-I(F46G), apoC-I(F42A/F46A), apoC-I(F42G), and apoC-I(F42G/F46G) bind significantly weaker to DMPC with Kd(app) of 2.24 microM, 3.07 microM, 4.24 microM, and 10.1 microM, respectively. Sedimentation velocity studies subsequently show that the protein/DMPC complexes formed by these apoC-I mutants sediment at 6.5S, 6.7S, 6.5S, and 8.0S, respectively. This is compared with 5.0S for WT apoC-I, suggesting the shape of the particles was different. Transmission electron microscopy confirmed this assertion, demonstrating that WT forms discoidal complexes with a length-to-width ratio of 2.57, compared with 1.92, 2.01, 2.16, and 1.75 for apoC-I(F42G), apoC-I(F46G), apoC-I(F42A/F46A), and apoC-I(F42G/F46G), respectively. Our study demonstrates that the C-terminal amphipathic alpha-helix of human apoC-I contains the major lipid-binding determinants, including important aromatic residues F42 and F46, which we show play a critical role in stabilizing the structure of apoC-I, mediating phospholipid interactions, and promoting discoidal particle morphology.
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ItemContinuous flow based catch and release protocol for the synthesis of alpha-ketoesters(BEILSTEIN-INSTITUT, 2009-05-20)Using a combination of commercially available mesofluidic flow equipment and tubes packed with immobilised reagents and scavengers, a new synthesis of alpha-ketoesters is reported.
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ItemNo Preview AvailableMembrane-targeted strategies for modulating APP and A beta-mediated toxicity(WILEY, 2009-02-01)Alzheimer's disease (AD) is a progressive neurodegenerative disease characterized by numerous pathological features including the accumulation of neurotoxic amyloid-beta (Abeta) peptide. There is currently no effective therapy for AD, but the development of therapeutic strategies that target the cell membrane is gaining increased interest. The amyloid precursor protein (APP) from which Abeta is formed is a membrane-bound protein, and Abeta production and toxicity are both membrane mediated events. This review describes the critical role of cell membranes in AD with particular emphasis on how the composition and structure of the membrane and its specialized regions may influence toxic or benign Abeta/APP pathways in AD. The putative role of copper (Cu) in AD is also discussed, and we highlight how targeting the cell membrane with Cu complexes has therapeutic potential in AD.
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ItemSetting and meeting priorities in Indigenous health research in Australia and its application in the Cooperative Research Centre for Aboriginal health.(Springer Science and Business Media LLC, 2009-11-20)Priority setting is about making decisions. Key issues faced during priority setting processes include identifying who makes these decisions, who sets the criteria, and who benefits. The paper reviews the literature and history around priority setting in research, particularly in Aboriginal health research. We explore these issues through a case study of the Cooperative Research Centre for Aboriginal Health (CRCAH)'s experience in setting and meeting priorities.Historically, researchers have made decisions about what research gets done. Pressures of growing competition for research funds and an increased public interest in research have led to demands that appropriate consultation with stakeholders is conducted and that research is of benefit to the wider society. Within Australian Aboriginal communities, these demands extend to Aboriginal control of research to ensure that Aboriginal priorities are met.In response to these demands, research priorities are usually agreed in consultation with stakeholders at an institutional level and researchers are asked to develop relevant proposals at a project level. The CRCAH's experience in funding rounds was that scientific merit was given more weight than stakeholders' priorities and did not necessarily result in research that met these priorities. After reviewing these processes in 2004, the CRCAH identified a new facilitated development approach. In this revised approach, the setting of institutional priorities is integrated with the development of projects in a way that ensures the research reflects stakeholder priorities.This process puts emphasis on identifying projects that reflect priorities prior to developing the quality of the research, rather than assessing the relevance to priorities and quality concurrently. Part of the CRCAH approach is the employment of Program Managers who ensure that stakeholder priorities are met in the development of research projects. This has enabled researchers and stakeholders to come together to collaboratively develop priority-driven research. Involvement by both groups in project development has been found to be essential in making decisions that will lead to robust and useful research.
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ItemCrystal structure of A(3)B(3) complex of V-ATPase from Thermus thermophilus(WILEY, 2009-12-02)Vacuolar-type ATPases (V-ATPases) exist in various cellular membranes of many organisms to regulate physiological processes by controlling the acidic environment. Here, we have determined the crystal structure of the A(3)B(3) subcomplex of V-ATPase at 2.8 A resolution. The overall construction of the A(3)B(3) subcomplex is significantly different from that of the alpha(3)beta(3) sub-domain in F(o)F(1)-ATP synthase, because of the presence of a protruding 'bulge' domain feature in the catalytic A subunits. The A(3)B(3) subcomplex structure provides the first molecular insight at the catalytic and non-catalytic interfaces, which was not possible in the structures of the separate subunits alone. Specifically, in the non-catalytic interface, the B subunit seems to be incapable of binding ATP, which is a marked difference from the situation indicated by the structure of the F(o)F(1)-ATP synthase. In the catalytic interface, our mutational analysis, on the basis of the A(3)B(3) structure, has highlighted the presence of a cluster composed of key hydrophobic residues, which are essential for ATP hydrolysis by V-ATPases.
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ItemProtein secretion and outer membrane assembly in Alphaproteobacteria(OXFORD UNIV PRESS, 2008-11-01)The assembly of beta-barrel proteins into membranes is a fundamental process that is essential in Gram-negative bacteria, mitochondria and plastids. Our understanding of the mechanism of beta-barrel assembly is progressing from studies carried out in Escherichia coli and Neisseria meningitidis. Comparative sequence analysis suggests that while many components mediating beta-barrel protein assembly are conserved in all groups of bacteria with outer membranes, some components are notably absent. The Alphaproteobacteria in particular seem prone to gene loss and show the presence or absence of specific components mediating the assembly of beta-barrels: some components of the pathway appear to be missing from whole groups of bacteria (e.g. Skp, YfgL and NlpB), other proteins are conserved but are missing characteristic domains (e.g. SurA). This comparative analysis is also revealing important structural signatures that are vague unless multiple members from a protein family are considered as a group (e.g. tetratricopeptide repeat (TPR) motifs in YfiO, beta-propeller signatures in YfgL). Given that the process of the beta-barrel assembly is conserved, analysis of outer membrane biogenesis in Alphaproteobacteria, the bacterial group that gave rise to mitochondria, also promises insight into the assembly of beta-barrel proteins in eukaryotes.
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Item4-Chloroanilinium 2-carboxy-4,5-dichlorobenzoate(WILEY-BLACKWELL, 2009-09-01)The structure of the 1:1 proton-transfer compound of 4-chloro-aniline with 4,5-dichloro-phthalic acid (DCPA), viz. C(6)H(7)ClN(+)·C(8)H(3)Cl(2)O(4) (-), has been determined at 130 K. The non-planar hydrogen phthalate anions and the 4-chloro-anilinium cations form two-dimensional O-H⋯O and N-H⋯O hydrogen-bonded substructures which have no peripheral extension. Between the sheets there are weak π-π associations between alternating cation-anion aromatic ring systems [shortest centroid-centroid separation = 3.735 (4) Å].
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Item1,10-Phenanthrolin-1-ium 2-carboxy-4,5-dichlorobenzoate(WILEY-BLACKWELL, 2009-10-01)In the structure of the 1:1 proton-transfer compound of 1,10-phenanthroline with 4,5-dichloro-phthalic acid, C(12)H(9)N(2) (+)·C(8)H(3)Cl(2)O(4) (-), determined at 130 K, the 1,10-phenanthrolinium cation and the hydrogen 4,5-dichloro-phthalate anion associate through a single N-H⋯O(carbox-yl) hydrogen bond giving discrete units which have no extension except through a number of weak cation C-H⋯O(anion) associations and weak cation-anion aromatic ring π-π inter-actions [minimum centroid-centroid separation = 3.6815 (12) Å]. The anions are essentially planar "[maximum deviation 0.214 (1) Å (a carboxyl O)] with the syn-related H atom of the carboxyl group, forming a short intra-molecular O-H⋯O(carbox-yl) hydrogen bond.
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Item2-carboxyquinolinium-2,4,6-trinitro-benzenesulfonate -quinolinium-2-carboxylate (1/1/1)(BLACKWELL PUBLISHING, 2008-01-01)The structure of the title adduct compound, C(10)H(8)NO(2) (+)·C(6)H(2)N(3)O(9)S(-)·C(10)H(7)NO(2), from the reaction of 2,4,6-trinitro-benzene-sulfonic acid (picrylsulfonic acid) with quinoline-2-carboxylic acid (quinaldic acid) in 2-propanol-water, has been determined at 130 (2) K. The cation and the adduct species form a twisted cyclic hydrogen-bonded R(2) (2)(10) pseudo-dimer which is extended into a one-dimensional chain structure through short head-to-tail carboxylic acid O-H⋯O(carbox-yl) associations [O⋯O = 2.4711 (19) Å]. The picrylsulfonate anions are attached peripherally by single N-H⋯O(sulfonate) hydrogen bonds [N⋯O = 2.8643 (19) Å].
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ItemMinimising oil droplet size using ultrasonic emulsification(ELSEVIER, 2009-08-01)The efficient production of nanoemulsions, with oil droplet sizes of less than 100nm would facilitate the inclusion of oil soluble bio-active agents into a range of water based foods. Small droplet sizes lead to transparent emulsions so that product appearance is not altered by the addition of an oil phase. In this paper, we demonstrate that it is possible to create remarkably small transparent O/W nanoemulsions with average diameters as low as 40nm from sunflower oil. This is achieved using ultrasound or high shear homogenization and a surfactant/co-surfactant/oil system that is well optimised. The minimum droplet size of 40nm, was only obtained when both droplet deformability (surfactant design) and the applied shear (equipment geometry) were optimal. The time required to achieve the minimum droplet size was also clearly affected by the equipment configuration. Results at atmospheric pressure fitted an expected exponential relationship with the total energy density. However, we found that this relationship changes when an overpressure of up to 400kPa is applied to the sonication vessel, leading to more efficient emulsion production. Oil stability is unaffected by the sonication process.