Intrinsic factor-mediated modulation of cyanocobalamin–N-sulfonyl-acridinium-9-carboxamide chemiluminescence

Two cyanocobalamin–N-sulfonyl-acridinium-9-carboxamides with linkage through the N10 or 9-position were prepared from B12-e-carboxylic acid. The noncovalent association of intrinsic factor with these ligands resulted in specific modulation of the associated chemiluminescence signal either by quenching or changing the emission profile. Either effect was sufficient to formulate a homogeneous assay to detect vitamin B12 in buffer.