RegistryNo. Methyl benzoate, 93-58-3; phenyl benzoate, 93-99-2; methyl formate, 107-31-3; methyl acetate, 79-20-9; vinyl acrylate, 2177-18-6; formic acid, 64-18-6; benzoic acid, 65-85-0.

No abstract

The second messenger c-di-GMP is a key regulator of bacterial physiology. The V. vulnificus genome encodes nearly 100 proteins predicted to make, break, and bind c-di-GMP. However, relatively little is known regarding the environmental signals that regulate c-di-GMP levels and biofilm formation in V. vulnificus. Here, we identify calcium as a primary environmental signal that specifically increases intracellular c-di-GMP concentrations, which in turn triggers brp-mediated biofilm formation. We show that PAPS, a metabolic intermediate of the sulfate assimilation pathway, acts as a second messenger linking environmental calcium and sulfur source availability to the production of another intracellular second messenger (c-di-GMP) to regulate biofilm and rugose colony formation, developmental pathways that are associated with environmental persistence and efficient bivalve colonization by this potent human pathogen.

The crystal structure of poly-@-phenylene terephthalate), PPT, has been determined using a combination of molecular modelling and X-ray powder diffractio!. The polyTer is found !o crystallize in the monoclinic space group, P2,/a, with unitcell parameters a = 7.98 A, b = 5.33 A, c = 12.65 A and #? = 98.98" at 25°C. The crystal packing favours intermolecular phenyl-edge to phenyl-face and carbonylcarbon to carbonyl-oxygen interactions over other possibilities. The method used to predict the structure consisted of several distinct stages. Initially, a database of structural information relevant to the component units of the polymer was assembled. A molecular modelling program was used to construct and manipulate model crystals based on this information and energy calculations employed to discard those which were energetically unlikely, or sterically impossible. Finally, powder diffraction patterns were simulated for the remaining models and compared with experimental data. Likely candidates for the crystal structure were then iteratively refined, to improve the agreement between simulation and experiment. The method is particularly useful for solving structures of polymers which, as in the present case, are unable to form large single crystals or oriented fibres.

Structure formation in liquid crystalline polymers involves processes at different length scales.The key stages are the molecular conformations which are the basis of the tendency to form a liquid crystalline phase, and the mesoscale texture of the nematic director field, involving distortion elasticity due to defects. This paper outlines computer modelling at these different length scales as well as an approach towards linking the scales by means of calculating mesoscale model parameters from the molecular modelling. The molecular modelling stage involves the calculation of torsional potentials associated with the backbone of the polymer. These energy functions are required for generating an ensemble of chains from which the persistence length can be determined. The molecular data are used to parameterize the mesoscale modelling: Frank elastic constants, rotational diffusion constant and Ericksen shape parameter are determined. On the mesoscale, a lattice model for the director field is formulated.A Monte Carlo algorithm is employed to study the annealing of the director microstructure.Shearing is added via the Ericksen equation and a dynamics model allows simulation of flow of the director field under constant shear. As an example we study the thermotropic aromatic copolyester Vectra A.