Utilization of Chromatographic and spectroscopic techniques to study the oxidation kinetics of selenomethionine

Abstract

Ion-exchange LC and spectroscopic supporting techniques have been successfully used to study the kinetics and mechanism of oxidation reactions of selenomethionine (SeMet). Oxidation of selenomethionine with both cyanogen bromide (CNBr) and hydrogen peroxide (H(2)O(2)) proceeds through a stable intermediate which undergoes cyclization and C-Se bond cleavage to form 2-amino-4-butyrolactone. This stable intermediate was identified by IR spectroscopy as methionine dihydroxy selenide. The CH(3)-Se moiety of SeMet formed methyl selenic acid upon reaction with H(2)O(2) and methyl selenocyanate (CH(3)SeCN), characterized by GC-MS, for the reaction with CNBr. Both reactions were of apparent first order with respect to the concentration of SeMet. A rate constant (k(1))of 4.0x10(-3) s(-1) for the reaction of SeMet with HO and 4.0x10(-3) s(-1) for the reaction with CNBr were determined at a temperature of 22 degrees C. Oxidation of methionine (Met) gives disparate kinetics and oxidation products from SeMet. Thus the differential rate method can be utilized to quantitatively separate SeMet in biological samples in the presence of much higher concentrations of Met.

Element selective characterization of stability and reactivity of selenium species in selenized yeast

“…The formation of the hydrate under such acid conditions has been reported elsewhere. 30,31 The mass spectrum of oxidized selenomethionine was confirmed as reported by Bird to indicate the presence of hydrated selenomethionine selenoxide with a selenium ion cluster (Se-80 molecular ion at m/z 232). 32 Larsen et al have described an ion exchange HPLC-ICP-MS study in which selenomethionine selenoxide was observed and confirmed.…”

Bioavailability of selenium from selenium-enriched green onions (Allium fistulosum) and chives (Allium schoenoprasum) after ‘in vitro’ gastrointestinal digestion

“…Se(IV) 1,000 mg/l stock solution was obtained from Merck. Selenomethionine-Se-oxide (SeOMet) was prepared as presented previously (Zainal et al 1996). For chromatographic purposes, NH 4 H 2 PO 4 , NH 4 OH, H 3 PO 4 , concentrated HCOOH, HCl, NaOH and pyridine were obtained from Reanal (Budapest, Hungary).…”

Reactivity of selenomethionin – dents in the magic bullet?

“…The mechanism and products of the spontaneous oxidation of SeMet are unknown, and the literature of Se chemistry is not terribly helpful in identifying likely candidates. Spontaneous breakdown of SeMet in aqueous solution has been reported [5], although temperatures above ambient or storage in sunlight were required for breakdown on a timescale of one year [6]. Neither of these studies addressed the question of SeMet breakdown within a protein.…”