Photolytic properties of the biologically active forms of vitamin B12

摘要: Abstract The biologically active forms of vitamin B12, methylcobalamin (MeCbl) and adenosylcobalamin (AdoCbl), are important cofactors in a variety enzymatic processes. In addition to their roles as cofactors, these B12 derivatives have unique photolytic properties based on the light-sensitivity organometallic Co C bond. Their photolysis is mediated by low-lying excited states, where photodissociation bond leads formation singlet-born alkyl/cob(II)alamin radical pairs (RPs). Also, geometric electronic characteristics cobalamins (Cbls) different whether 5,6-dimethylbenzimidazole base (DBI) bound lower axial ligand (base-on) or replaced water (base-off) strongly acidic conditions. focus this review summarize current understanding from theoretical perspective. Potential energy surfaces (PESs) associated with constructed functions both lengths, provide most reliable tool for mechanisms. primary computational method calculating ground state density functional theory (DFT), while time-dependent DFT (TD-DFT) used electronically states. Based such PESs, pathways connecting metal-to-ligand charge transfer (MLCT) field (LF) can be light induced photo-homolysis that observed experimentally. Likewise, crossing S1/S0 describe internal conversion (IC) state. Particular emphasis will placed differences mechanisms base-on versus base-off cofactors. possibility intersystem (ISC) triplet RP also presented semi-classical Landau-Zener theory.