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ItemProtein secretion and outer membrane assembly in AlphaproteobacteriaGatsos, X ; Perry, AJ ; Anwari, K ; Dolezal, P ; Wolynec, PP ; Likic, VA ; Purcell, AW ; Buchanan, SK ; Lithgow, T (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.
Item2-carboxyquinolinium-2,4,6-trinitro-benzenesulfonate -quinolinium-2-carboxylate (1/1/1)Smith, G ; Wermuth, UD ; White, JM (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].
ItemHydrodynamic boundary conditions and dynamic forces between bubbles and surfacesManor, O ; Vakarelski, IU ; Tang, X ; O'Shea, SJ ; Stevens, GW ; Grieser, F ; Dagastine, RR ; Chan, DYC (AMER PHYSICAL SOC, 2008-07-11)Dynamic forces between a 50 microm radius bubble driven towards and from a mica plate using an atomic force microscope in electrolyte and in surfactant exhibit different hydrodynamic boundary conditions at the bubble surface. In added surfactant, the forces are consistent with the no-slip boundary condition at the mica and bubble surfaces. With no surfactant, a new boundary condition that accounts for the transport of trace surface impurities explains variations of dynamic forces at different speeds and provides a direct connection between dynamic forces and surface transport effects at the air-water interface.
ItemReversible Redox Reactions in an Extended Polyoxometalate Framework SolidRITCHIE, CHRISTOPHER ; Streb, Carsten ; Thiel, Johannes ; Mitchell, Scott, G ; Miras, Haralampos, N ; De-Liang, Long ; Boyd, Thomas ; Peacock, Robert. D ; McGlone, Thomas ; Cronin, Leroy ( 2008)