Fractional electrical transport studies of vitamin B12 binding by proteins.

Bird and Hoevet (1) have described a procedure for measuring the vitamin Blz-binding capacity of protein mixtures derived from hog mucosa, based on the non-dialyzability of the protein-bound vitamin. They also observed that lysozyme would bind vitamin B1, as previously reported (3), but that it did not appear to retain the vitamin when dialyzed. However, the diffusibility of lysozyme through cellophane membranes has been demonstrated (2, S), and the possibility of a diffusible vitamin-lysozyme complex is not precluded. Ross (7) has observed the binding of vitamin Blz in normal and pathological (pernicious anemia) human sera and has studied the conditions for heat release of the bound vitamin. The question of the number of proteins which might contribute to the over-all binding capacity of various protein preparations (especially those containing a proportion of the intrinsic factor principle) is of some interest. Therefore, the following experiments involving the mobilization of proteins by electrical transport and a study of their relative abilities to bind vitamin B12 were undertaken.