Vitamin Bia

As we know at present, the mucoproteose fraction includes the following materials (1) most of the gastric fucomucins, as well as some of the blood group substances, i.e., most of the neutral polysaccharides of the dissolved mucin fraction linked to their peptide moiety, (2) y-globulin and probably also P-globulin, which pass into the gastric juice from the serum (G16, G42, Hll, H20, H55) and probably account for the presence of mannose in this fraction (Gll), (3) some of the pep-tidic degradation products of serum albumin and visible mucus, which are partly dialyzable (G16, K2), (4) native intrinsic factor, the related primary vitamin Bi2 binder, and tertiary vitamin Bia binder related to the neutral mucosubstances (G14, Ul, U2). 

Coenzyme form of vitamin Bia containing Co—C bond is reported. 

Pratt, J. M., Inorganic Chemistry of Vitamin Bia. Academic Press, New York, 1971. 

Vitamers are chemically similar substances that have a qualitatively similar vitamin activity. Thus, vitamin D refers to ergocalciferol (Da) and cholecalciferol (D3) and sometimes to their 25-hydroxy- and 1,25-dihydroxy derivatives (Chapter 37). Similarly, pyridoxine (pyri-doxol), pyridoxal, and pyridoxamine are vitamin Be vitamers, riboflavin is the active form of vitamin Ba and cobalamin is vitamin Bia- The members of a particular vitamin family are functionally interchangeable and protect against deficiency symptoms for that vitamin. A vitamin and its corresponding deficiency disease are related as follows ... 

Vitamin Bia status in oral contraceptive users has received less attention than that of folate, possibly in part because there have been no reported cases of megaloblastic anemia with evidence of B12 deficiency in OCA-users. All women with apparent folate deficiency anemia in association with use of OCAs (see above) had normal serum B12 levels in those instances in which it was measured. 

Cobalt(i).—The main interest here is in cobaloximes and similar cobalt(i) chelate complexes as models for reduced forms of vitamin Big. Kinetic studies of alkylation at cobalt(i), as in the recent study of reaction of alkyl halides with, for example, cobaloximes and vitamin Bias, indicate an 5 n2 mechanism, with cobalt(i) acting as a very strong nucleophile. The 5 n2 mechanism has now been confirmed stereochemically by establishing that these reactions proceed with inversion of configuration at carbon. Reaction of vinyl halides with these cobalt(i) complexes also proceeds by an associative nucleophilic substitution mechanism, rather than via acetylenic intermediates. ... 

Fig. 2. Absorption spectra of the coenzyme form of pseudovitamin Bij (coenzyme) and of cyanocobalamin (vitamin Bia) in neutral aqueous solution.

Cobalamin(i) (Vitamin Bias) is formed in the pulse radiolysis reduction of cobalamin(ii) (Vitamin Bjar) and reacts with NaO to release Na ... 

Cobalt.— The kinetics and ma hanisms of reactions involving cobalt-carbon bond cleavage and formation have been discussed in review articles on vitamin Bia and cobaloxime model complexes. Interest in these systems... 

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