title: Co-C bond dissociation energy and reaction volume change of 2',5'-dideoxyadenosylcobalamin studied by laser-induced time-resolved photoacoustic calorimetry.
abstract: Time resolved photoacoustic calorimetry (PAC) was applied to a study of the photolysis of a coenzyme B(12) analog 2',5'-dideoxyadenosylcobalamin, which lacks an -OH group at the 2' position of ribofuranose ring. In aqueous solution, we report for the first time the quantum yield Phi(d) (0.25+/-0.02), Co-C bond dissociation energy (BDE; 31.8+/-2.5 kcal mol(-1)) and reaction volume change deltaV(R) (6.5+/-0.5 ml mol(-1)) due to conformation changes of the corrin ring and its side chains accompanying the cleavage of the Co-C bond. These values for the analog are very similar to those for the natural cofactor. Based our results and previous studies, a possible explanation for the similarity in their structure and properties versus the large difference in their enzymatic activity is discussed.
mesh_terms: D002151:Calorimetry; D002244:Carbon / Q000737:chemistry*; D003035:Cobalt / Q000737:chemistry*; D013816:Thermodynamics; D014805:Vitamin B 12 / Q000031:analogs & derivatives* / Q000737:chemistry*
chemical_list: C096700:2',5'-dideoxyadenosylcobalamin; D003035:Cobalt; D002244:Carbon; D014805:Vitamin B 12