Electron spin resonance of spin trapped radicals in γ-irradiated polycrystalline dipeptides. Chromatographic separation of radicals

Abstract

KEIsUKE MAKINO and PETER RIESZ. Can. J. Chem. 60, 1480Chem. 60, (1982. Polycrystalline dipeptides (glycyl-glycine, glycyl-L-valine, glycyl-L-leucine, L-alanyl-glycine, and L-prolyl-L-alanine) were y-irradiated at room temperature in the absence of air. Subsequently they were dissolved in aqueous solutions containing 2-methyl-2-nitrosopropane as the spin trap. From the esr spectra of the nitroxide radicals separated by high-performance liquid chromatography, structural assignments of the radicals were made. For glycyl peptides, H-abstraction from the a-carbon atoms of the carboxyl terminal residues and from the side-chains were observed. For L-alanyl-glycine, H-abstraction from the glycyl residue and the formation of the deamination radical could be shown to occur. For L-prolyl-L-alanine, the ring opening (deamination) reaction, decarboxylation and H-abstraction from the C-terminal a-carbon were seen. KEISUKE MAKINO et PETER RIESZ. Can. J. Chem. 60, 1480 (1982). On a irradie aux rayons y, a la temperature ambiante et en I'absence d'air, les dipeptides polycristallins suivants:On les a ensuite dissous dans des solutions aqueuses contenant le capteur de spin, methyl-2 nitroso-2 propane. A partir des spectres de rpe des radicaux nitroxydes, skpares par chromatographie en phase liquide a haute performance, on a pu determiner les structures des radicaux. On a observe, dans le cas des peptides glycidiques, I'klimination d'un hydrogene partir des atomes de carbone en a du residue terminal carbxyle e t a partir des chaines laterales. Dans le cas du L-alanyl-glycine, on peut montrer qu'il se k~roduit unr 4limination d'hydrogene a partir du risidu glycyle et la formation d'un radical de desamination. Dans le cas du L-prolyl-L-alanine, on a observe une reaction d'ouverture de cycle (desamination), de decarboxylation et d'0limination d'un atome d'hydrogene a partir du carbone terminal en position 2.[Traduit par le journal]

Inorganic radicals of relevance to biological systems

“…Fortunately, if OH' radicals react with large biopolymers, the resulting bio-radicals may not react efficiently with the traps, and the adducts, once formed, may give very broad-lined spectra because of slow tumbling rates. If several nitroxide radicals are formed concurrently, and are sufficiently stable, they can be separated by using high-pressure liquid chromatography (Moriya et al 1982;Makino & Riesz 1982), greatly facilitating spectral analysis.…”