Surface-Enhanced Raman-Spectroscopy Of Bilirubin-Metal Ion Complexes

Surface-Enhanced Raman Scattering (SERS) spectra of bilirubin-metal ion (Cu2+, Co2+, Zn2+, Cd2+) complexes (MBR) are reported. These spectra reveal significant differences between MBR and bilirubin (BR) itself. But SERS spectra of bilirubin-Cu2+, Co2+, Zn2+, Cd2+ complexes are similar to each other. The mole ratio of bilirubin-metal in the complexes M(2+):BR = 1:1 was measured. Empirical assignments of the major SERS bands are given. The spectrum of CuBR in solution is consistent with a square planar structure. It should be noted, however, that H2O or COOH of another BR molecule occupy the positions above and below the plane in solutions of complexes of this type and forms Cu-O bond.By comparing the SERS spectra of bilirubin-copper (or zinc) and biliverdin-copper (or zinc) complexes, the similar Raman frequencies and relative intensities were attributed to the oxidation of the bilirubin-copper (or zinc) complex to the green biliverdin-copper (Zn) complexes. It is shown that M(2+) + BR --> MBR + 2H(+)[GRAPHICS]MBV. (C) 1995 John Wiley & Sons,Inc.