Resonance Raman active vibrations of blue copper proteins. Normal coordinate analysis on 169-atom model.

Normal coordinate analyses were performed for three crystallographically defined blue copper proteins: Alcaligenes denitrificans azurin, Pseudomonas aeruginosa azurin, and poplar leaf plastocyanin. A maximum of 485 internal coordinates were specified from a model constructed by the analyzed coordinates of the 169 atoms around the type-1 blue copper site. Mass-group approximation was employed for CH, CH2, CH3, NH, and NH2 groups throughout. With the use of reasonable force constant values, the standard GF calculation method always gives rise to extensive couplings of Cu–S(cysteine) stretching coordinate to the bending coordinates widely distributed in the molecule. Several normal vibrational modes having appreciable PED values of the Cu–S(cysteine) stretching coordinate are correlated with the characteristic RR lines of the blue copper proteins in the 370–450 cm−1 region. Our data indicate that the protein-sensitive variation of the RR pattern might be ascribed to a difference in the peptide structure arou...