H-2-LABELED AND C-13-LABELED AMINO-ACIDS GENERATED BY OBLIGATE METHYLOTROPHS BIOSYNTHESIS AND MS MONITORING

Biosynthetic preparation of H-2- and C-13- labeled amino acids was stu died using a leucine-producing mutant of the obligate methylotroph, Me thylobacillus flagellatum. The strain was cultivated in various media containing C-13- or H-2-analogs of methanol. The total protein from ea ch experiment was subjected to acid hydrolysis and converted into a mi xture of dansyl amino acid methyl esters. The samples of excreted leuc ine were converted into methyl esters of dansyl and benzyloxycarbonyl derivatives. Electron impact mass spectrometry was performed to detect stable isotope enrichment of the amino acids. According to the mass s pectrometric analysis it is feasible to use methylotrophic microorgani sms for the preparation of H-2- and C-13- analogs of amino acids by la beled methanol bioconversion; the excreted amino acids can be convenie nt for express analysis as an indicator of isotopic enrichment of the total protein. The data obtained testified to a high efficiency of dan syl derivatization for mass spectrometric analysis of complex amino ac id mixtures.