Difference circular dichroism studies of copper and nickel binding to D-penicillamine in the presence of human serum albumin.

The binding of copper and nickel to D-penicillamine in the presence of human serum albumin (HSA) has been studied using difference circular dichroism (CD). The difference CD spectra due to penicillamine in HSA-Cu2+-penicillamine systems at pH 6 are indicative of ternary complexes between HSA, copper and penicillamine. On the other hand, the difference spectra due to penicillamine in HSA-Ni2+-penicillamine systems resemble that due to the Ni2+-penicillamine complex, indicating that mostly binary complexes are formed. The formation of stable complexes between penicillamine and copper or nickel (whether they are of the binary or mixed ligand type) may be important in the therapeutic action of this drug.