title: A precursor in the photolytic cleavage of the Co (III)-C bond of coenzyme B-12 unobservable by electron paramagnetic resonance.
abstract: Photolysis of a frozen (80--200 K) anaerobic solution of 5'-deoxyadenosyl-cobalamin in aqueous propan-1,2-diol produces only a small Co(II) signal detectable by electron paramagnetic resonance (EPR). Upon warming to room temperature and refreezing without further irradiation the Co(II) signal increases many-fold. The interpretation is that at low temperature there is an EPR-undetectable "incipient" homolysis of the Co-C bond of the coenzyme which is revealed at higher temperature. The possible implications of this observation for the coenzyme B-12-dependent enzymes are noted.
mesh_terms: D055598:Chemical Phenomena; D002621:Chemistry; D003035:Cobalt; D003038:Cobamides; D004578:Electron Spin Resonance Spectroscopy; D010782:Photolysis; D013696:Temperature
chemical_list: D003038:Cobamides; D003035:Cobalt