Crystallization of Arthrobacter sp. strain 1C N-(1-D-carboxyethyl)-L-norvaline dehydrogenase and its complex with NAD+

The novel NAD+-linked opine dehydrogenase from a soil isolate Arthrobacter sp. strain 1C belongs to an enzyme superfamily whose members exhibit quite diverse substrate specificites. Crystals of this opine dehydrogenase, obtained in the presence or absence of co-factor and substrates, have been shown to diffract to beyond 1.8 ? resolution. X-ray precession photographs have established that the crystals belong to space group P21212, with cell parameters a = 104.9, b = 80.0, c = 45.5 ? and a single subunit in the asymmetric unit. The elucidation of the three-dimensional structure of this enzyme will provide a structural framework for this novel class of dehydrogenases to enable a comparison to be made with other enzyme families and also as the basis for mutagenesis experiments directed towards the production of natural and synthetic opine-type compounds containing two chiral centres.     

Synthesis of the C(1)-C(12) segment of peloruside A by an alpha-benzyloxymethyl ketone aldol strategy

The C(1)-C(12) segment of 16-membered antitumor macrolide peloruside A has been prepared by a BF(3).OEt(2)-catalyzed Mukaiyama aldol reaction between a glucose-derived C(1)-C(7) aldehyde and a C(8)-C(12) alpha-benzyloxymethyl ketone. Exclusive 2,3-anti and moderate 3,5-anti/syn facial selectivity (3.5:1) was observed in the aldol reaction. The key C(1)-C(7) aldehyde contains the required stereochemistry at carbons two, three, and five, and has been efficiently prepared on multigram scales from commercial triacetyl D-glucal. [reaction: see text]     

Computable error bounds for pointwise derivatives of a Neumann problem

In this paper we discuss the recovery of derivatives and thecomputation of rigorous and useful upper bounds for the pointwiseerror in the recovered derivatives, for finite element approximationsof the Laplace equation with Neumann boundary conditions, especiallyat points close to or on a smooth, curved boundary. We analyzethe dipole image technique for the case of curved boundaries,and show how to compute reliable recovered derivatives and errorbounds even in the limiting case of points lying on the curvedboundary. Numerical experiments show reasonably tight errorbounds for points both close to and away from a curved boundary.     

Zur Anwendung der Methode der Phasenintegrale auf das Wasserstoffmolekülion

Zeitschrift für Physik A Hadrons and nuclei - Es wird angegeben, wie man in dem Falle des H 2 + die angenäherte Bestimmung der stationären Zustände mittels der verfeinerten...     

Polar nanoregions in Pb(Mg<Subscript>1/3</Subscript>Nb<Subscript>2/3</Subscript>)O<Subscript>3</Subscript> (PMN): insights from a supercell approach

We report construction of a model of polar nanoregions in the PMN relaxor ferroelectric based on first-principles lattice dynamics for chemically ordered supercells [S.A. Prosandeev et al., Phys. Rev. B 70, 134110 (2004)], combined with invariance under permutations and dipole-dipole interaction as a source supporting randomly oriented residual polarization. Representative analytical estimates of polar nanore-gion — supercell mapping reproduce both nonzero local and zero macroscopic polarization of the structure, as well as the temperature change of the supercell anisotropy at cooling and field cooling.     

Polymer-supported tetrafluorophenol: a new activated resin for chemical library synthesis

A new tetrafluorophenol activated resin that facilitates the use of 19F NMR to quantitate loading is presented. This new resin provides a useful tool for acylation, and a novel activated polymeric sulfonate ester to generate sulfonamides. This activated resin reacts with a wide scope of N-nucleophiles including primary and secondary amines, and anilines. This new activated resin methodology provides a powerful tool for pure single-compound library synthesis.