| abstract |
The present invention is concerned with novel derivatives of cyanocobalamin (vitamin B 12 ), especially of the monocarboxylic acid hydrolysates thereof, by which (1) an antigenic conjugate thereof with a protein is obtainable and (2) a readily iodinatable aromatic ring can be introduced while retaining in each instance, the essential constitution of cyanocobalamin to such an extent that (a) the antigenic protein conjugate, when introduced into the blood stream of a vertebrate, causes the formation of an antibody which is specific to the cyanocobalamin portion of the conjugate and (b) unmodified cyanocobalamin and the second-mentioned derivative when tagged or labeled with radioactive-iodine competitively bind on the aforementioned antibody. Thus, the present invention provides cyanocobalamin derivatives which are quite useful in radioimmunoassay (RIA) of vitamin B 12 . |