Physical measurements of Cu{sup 2+}-complexes of bilirubin

Copper is known to form complexes with bilirubin (H{sub 2}BR). Such complexes have received increased attention due to their clinical significance as free-radical scavengers. The purpose of this study was to examine a series of Cu{sup 2+}BR complexes to ascertain the nature of the binding between Cu{sup 2+} and BR. Several physical measurements of the salts were made, such as Fourier Transform Infrared (FT-IR), Fourier Transform Raman spectroscopy (FT-R), and Electron Paramagnetic Resonance (EPR). The complexes were prepared by dissolving protonated BR in NaOH, and adding different ratios of aqueous CuCl{sub 2}. At ratios of Cu{sup 2+}:H{sub 2}BR of 1:1 and 2:1, soluble complexes were formed. In solution EPR spectra demonstrated 9 hyperfine peaks, which from the splitting, is indicative of Cu{sup 2+} coordinated to 4 nitrogen atoms coming from 2 molecules of BR