calf kidney has been used as a tissue source for the isolation of cobalamin analogues , which are defined here as cobalt-containing compounds of distinctive chromatographic behavior that are extractable from tissues by methods conventionally used to extract cobalamin and which , in radioisotope dilution assays , are more active with r-protein as binder than intrinsic factor and are relatively less active in microbiologic assays .
C2917443
cobalamin
C0042845
cobalamin