UTILIZATION OF CHROMATOGRAPHIC AND SPECTROSCOPIC TECHNIQUES TO STUDY THE OXIDATION-KINETICS OF SELENOMETHIONINE

Ion-exchange LC and spectroscopic supporting techniques have been succ essfully used to study the kinetics and mechanism of oxidation reactio ns of selenomethionine (SeMet). Oxidation of selenomethionine with bot h cyanogen bromide (CNBr) and hydrogen peroxide (H2O2) proceeds throug h a stable intermediate which undergoes cyclization and C-Se bond clea vage to form 2-amino-4-butyrolactone. This stable intermediate was ide ntified by IR spectroscopy as methionine dihydroxy selenide. The CH3-S e moiety of SeMet formed methyl selenic acid upon reaction with H2O2 a nd methyl selenocyanate (CH3SeCN), characterized by GC-MS, for the rea ction with CNBr. Both reactions were of apparent first order with resp ect to the concentration of SeMet. A rate constant (k(1)) of 4.0 x 10( -3) s(-1) for the reaction of SeMet with H2O2 and 4.0 x 10(-4) s(-1) f or the reaction with CNBr were determined at a temperature of 22 degre es C. Oxidation of methionine (Met) gives disparate kinetics and oxida tion products from SeMet. Thus the differential rate method can be uti lized to quantitatively separate SeMet in biological samples in the pr esence of much higher concentrations of Met.