SURFACE-ENHANCED RAMAN-SPECTROSCOPY OF BILIRUBIN-METAL ION COMPLEXES

Surface-Enhanced Raman Scattering (SERS) spectra of bilirubin-metal io n (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 si milar to each other. The mole ratio of bilirubin-metal in the complexe s 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 CO OH of another BR molecule occupy the positions above and below the pla ne in solutions of complexes of this type and forms Cu-O bond. By comp aring the SERS spectra of bilirubin-copper (or zinc) and biliverdin-co pper (or zinc) complexes, the similar Raman frequencies and relative i ntensities were attributed to the oxidation of the bilirubin-copper (o r zinc) complex to the green biliverdin-copper (Zn) complexes. It is s hown that M(2+) + BR --> MBR + 2H(+) [GRAPHICS] MBV. (C) 1995 John Wil ey & Sons,Inc.