Zur Photochemie von 2, 1-Benzisoxazolen (Anthranilen) und thermischen und photochemischen Umsetzungen von 2-Azido-acylbenzolen in stark saurer Lösung

Design and Synthesis of Visible Isotope-Coded Affinity Tags for the Absolute Quantification of Specific Proteins in Complex Mixtures

Identification of proteins in complex mixtures by mass spectrometry is most useful when quantitative data is also obtained. We recently introduced isotope-coded affinity tags (ICAT reagents) for the relative quantification of proteins present in two or more biological samples. In this report, we describe a new generation of ICAT reagents that contain the following additional features: (1) a visible tag that allows the electrophoretic position of tagged peptides during separation to be easily monitored; (2) a photocleavable linker that allows most of the tag to be removed prior to mass spectrometric analysis; (3) an isotope tag that contains carbon-13 and nitrogen-15 atoms instead of deuterium to ensure precise comigration of light and heavy tagged peptides by reverse-phase HPLC. These reagents contain an iodoacetyl group that selectively reacts with peptide cysteine residues. Peptide modification chemistry is also reported that allows tagging of peptides that are devoid of cysteine. The synthesis of these visible isotope-coded affinity tags (VICAT reagents), and their reaction with peptides are described in this report. VICAT reagents containing a carbon-14 visible probe or an NBD fluorophore are described. These reagents are most useful for the determination of the absolute quantity of specific target proteins in complex protein mixtures such as serum or cell lysates.

Synthesis and in vitro evaluation of substituted aryl- and hetarylmethyl phosphonate and phosphate — UMP derivatives as potential glucosyltransferase inhibitors

The enzyme β (1[Formula: see text]4)-glucosyltransferase (BGT) catalyses the transfer of glucose from uridine diphosphoglucose (UDP-Glc) to 5-hydroxymethylcytosine (5-HMC) bases in double-stranded DNA. Potential inhibitors of BGT were developed by structure-based design and synthesized. The designed inhibitors 1–6 provide conformational mimicry of the transition state in glucosyltransfer reactions. The key synthetic steps involve a Michaelis–Arbuzov reaction followed by coupling with uridine-5'-morpholidophosphate as activated UMP derivative. The compounds were tested for in vitro inhibitory activity against BGT and the inhibition kinetics were examined. Three of the designed molecules were found to be potential inhibitors of BGT having IC50values in the micromolar (µM) range. Useful structure–activity relationships were established which provide guidelines for the design of future generations of inhibitors of BGT.Key words: β-glucosyltransferase, transition state, enzyme inhibitors, structure-based design, synthesis.