Cobalamin and cobinamide

The electron spin resonance of the nitroxalkylcorrinoids can be readily observed in aqueous solution at room temperature. Both the cobalamin and cobinamide show nitrogen hyperfine coupling constants of 17.2 gauss. A typical spectrum is shown in Fig. 20. The line widths for the low, intermediate, and high field peaks are 1.87, 1.87, and 2.20... 

Two-Step Chemical Catalysis of the Reduction of Alkyl Halides by Low-Valent Cobalamins and Cobinamides... 

Chassaigne H and Lobinski R (1998a) Determination of cobalamins and cobinamides by microbore reversed phase HPLC with spectrophotometric ion-spray ionization MS and inductively coupled plasma MS detection. Anal Chim Acta 359 227-235. 

H-NMR Using the dependence of the proton-NMR chemical shift on pH, base atom B-2. .. gave a pK of 3.28 0.04. This value is in excellent agreement with die previously-reported value of 3.3 (ref. 122). pK values for cobalamins and cobinamides have been discussed. The limiting conductance of the cyanocobalamin ion is 33 mhos. 

Weinberg JB, Chen Y et al (2009) Inhibition of nitric oxide synthase by cobalamins and cobinamides. Free Radic Biol Med 46 1626-1632... 

Weinberg JB, Chen YC et al (2005) Cobalamins and cobinamides inhibit nitric oxide synthase enzymatic activity. Blood 106 2225... 

The fact that the nature of the ligands bound axially to the cobalt atom in the cobalamins and cobinamides profoundly influences the reactivity of the metal has received further confirmation from Hogenkamp and Holmes. They have measured the polarographic half-wave potential of several cobalamins and cobinamides and have shown that the differences in reactivity between the two series cannot be due solely to steric factors. 

The decomposition of alkylcobalamin by j8-elimination of H, whether by a route analogous to (18) or (20), is impossible in neopentyl and benzyl cobalamins and cobinamides. Schrauzer s group has studied the decomposition, in the absence and presence of O2, of such compounds. The slowness of the reaction under the first conditions points to reactions (14) and (26), equilibrium lying to the left in the former and the latter... 

Table 11.5. Activation Parameters for the Decomposition of Various Cobalamins and Cobinamides in Air (at pH 7), cf. Equation (14) for R = Pr and Bu B EHtnination Also Occurs...

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