Reactions of osmium tetraoxide with protein side chains and unsaturated lipids

Abstract

The reactions of OsO₄ with derivatives or model systems (L) for the side chains of tissue proteins have been studied, alone and in the presence of unsaturated lipids (R). The following new complexes have been isolated and their structures studied by vibrational and ¹H n.m.r. spectroscopy: Os₂O₆L₄(L =α-N-benzoyl-L-histidine isobutyl ester, imidazole, 1-methylimidazole, 5,6-dimethylbenzimidazole, n-butylamine, or α-N-benzoyl-DL-methionine); OsL₂(L = glutathione or L-cysteine); the mixed species Os₂O₆L₃L′(L = 1-methylimidazole, L′=L-proline methyl ester or α-N-benzoyl-L-arginine ethyl ester) and OsLL′_n(L = 1-methylimidazole, L′=α-N-benzoyl-L-cysteine or α-N-acetyl-L-cysteine); OsO₂(O₂R)L₂(R = cyclohexene, oleic acid, methyl oleate, or cholesteryl acetate; L = 1-methyl- and 5,6-dimethyl-benzimidazole, α-N-benzoyl-L-histidine isobutyl ester, or pyridine); Os₂O₄(O₄R)L₄ and Os₃O₆(O₆R′)L₆(R = methyl linoleate, R′= methyl linolenate; L = 1-methylimidazole). A possible role for OsO₄ in cross-linking proteins and lipids in biological tissue fixation is discussed.