Novel redox label for proteins.: Electron transfer properties of (η5-cyclopentadienyl) tricarbonyl manganese bound to bovine serum albumin

(η5-Cyclopentadienyl) tricarbonyl manganese (cymantrenyl) derivatives of the protein bovine serum albumin (BSA) with coupling ratios ranging from 7 to 20 were prepared by reaction of cymantrenyl methyl imidate with some of the lysine residues of BSA. Electrochemical measurements based on the AC voltammetric detection of the reduction of cymantrene bound to BSA protein were successfully set up in aqueous solutions and the detection limit of 2×10−7 M BSA was achieved. This limit is almost two orders of magnitude lower than that measured by IR spectroscopy. Electrochemical detection of cymantrene label will be used for immunoassay analysis of water-soluble analytes in our future work.