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.     

Oceanalin A, a hybrid alpha,omega-bifunctionalized sphingoid tetrahydroisoquinoline beta-glycoside from the marine sponge Oceanapia sp

[reaction: see text] The novel antifungal compound oceanalin A, an unprecedented "hybrid sphingolipid", was isolated from the marine sponge Oceanapia sp. The structure was elucidated using NMR and MS spectral analysis and chemical degradation. Oceanalin A exhibits in vitro antifungal activity against Candida glabrata with an MIC of 30 mug/mL.     

Improved biocompatibility of protein encapsulation in sol–gel materials

By using the fluorescent dye 6-propionyl-2-(N,N-dimethylamino) naphthalene (PRODAN) to monitor methanol generated during tetramethyl orthosilicate polymerization we have optimised the encapsulation of protein in silica sol–gel monoliths with respect to completion of hydrolysis and distillation in order to remove methanol such that protein can be added without denaturation. A minimum of 24 h at +4 °C was found to be required before hydrolysis is complete and 3–5 min of vacuum distillation at 50 °C and 300 mbar needed to remove methanol before the gel is formed. The biocompatibility of a tetramethyl orthosilicate sol–gel monolith was demonstrated by preserving the trimer protein allophycocyanin (APC) in its native form for up to 500 h. This obviates the previously essential requirement of covalently binding the trimer together in order to prevent dissociation into monomers and has enabled observation of native APC trimer in a sol–gel pore for the first time down to the single molecule level using combined fluorescence spectroscopy and confocal microscopy. The higher stability afforded by the protocol we describe could impact on the application of sol–gel materials to single-molecule studies of wider bearing such as protein folding and aggregation.     

A novel neoglycopeptide linkage compatible with native chemical ligation

The straightforward synthesis of a novel class of neoglycopeptide and its fusion with a larger peptide thioester using sequential chemoselective ligations is described.