title: Protein influence on the heme in cytochrome c: evidence from Raman difference spectroscopy.
abstract: Raman difference spectra have been obtained for the cytochromes c of a number of species by simultaneous data acquisition from two samples. Frequency differences as small as 0.1 cm-1 can be measured reproducibly by the technique we have developed. In comparisons between cytochromes c isolated from two different species, the frequency differences in the heme vibrational modes range from 0 to 6 cm-1. The vibrational frequencies of the heme are sensitive to the electronic charge density on the porphyrin macrocycle. The frequency differences are interpreted in terms of the influence of the heme-packed aromatic and highly electronegative amino acid side chains on the pi* charge density and distribution on the heme. Such a control of the electronic properties of the heme by the protein may be important for the function of cytochrome c.
mesh_terms: D000818:Animals; D001059:Apoproteins; D003574:Cytochrome c Group; D005399:Fishes; D000882:Haplorhini; D006418:Heme; D006736:Horses; D006801:Humans; D011487:Protein Conformation; D012441:Saccharomyces cerevisiae; D013059:Spectrum Analysis, Raman; D013329:Structure-Activity Relationship
chemical_list: D001059:Apoproteins; D003574:Cytochrome c Group; D006418:Heme