Selective Detection of Carbohydrates and Their Peptide Conjugates by ESI-MS Using Synthetic Quaternary Ammonium Salt Derivatives of Phenylboronic Acids

We present new tags based on the derivatives of phenylboronic acid and apply them for the selective detection of sugars and peptide-sugar conjugates in mass spectrometry. We investigated the binding of phenylboronic acid and its quaternary ammonium salt (QAS) derivatives to carbohydrates and peptide-derived Amadori products by HR-MS and MS/MS experiments. The formation of complexes between sugar or sugar-peptide conjugates and synthetic tags was confirmed on the basis of the unique isotopic distribution resulting from the presence of boron atom. Moreover, incorporation of a quaternary ammonium salt dramatically improved the efficiency of ionization in mass spectrometry. It was found that the formation of a complex with phenylboronic acid stabilizes the sugar moiety in glycated peptides, resulting in simplification of the fragmentation pattern of peptide-derived Amadori products. The obtained results suggest that derivatization of phenylboronic acid as QAS is a promising method for sensitive ESI-MS detection of carbohydrates and their conjugates formed by non-enzymatic glycation or glycosylation.

Microwave assisted oxidation of some aromatics by hydrogen peroxide at supported tungsten catalyst

Summary The oxidation of some arenes with the alkyl side groups by means of hydrogen peroxide is been presented. As the activator of hydrogen peroxide tungstoboric acid was chosen. The catalyst was examined under both homogeneous and heterogeneous conditions. The reactions under conventional conditions were compared with the microwave assisted reactions.     

Laser oscillation of Er3+:YVO4 and Er3+, Yb3+:YVO4 crystals in the spectral range around 1.6 μm

Laser oscillation around 1.6 μm was realised at room temperature for low-doped Er:YVO₄ crystals (0.5 at % and 1 at %) as well as for Er(1 at %), Yb(5 at %):YVO₄ crystal in continuous-wave mode. The maximum slope of the input–output curve was about 19% (vs. absorbed power) for Er(0.5 at %):YVO₄. The laser oscillation was discretely tunable in the spectral range between 1531 and 1604 nm. Received: 24. August 2000 / Published online: 8 November 2000