Abstract
Resonance Raman Spectra of heme proteins including hemoglobin (Hb), myoglobin (Mb), cytochrome-c (cyt-c), cyt-c3, cyt-b5 and modified (alkylated) cyt-c were measured in their reduced and oxidized states at various pH values. Raman spectra of single crystals of myoglobin derivatives were also measured and it was found that there are some structural changes of hemes on crystallization. The analysis of Raman spectra of Hb and Mb derivatives led us to conclude that the iron-ligand bonding in HbNO and MbNO is rather Fe3+-NO- than Fe2+-NO and also that the same type of bonding is deduced for external ligands including C2H5NC, CO and O2. Good correspondence of Raman lines of cyt-b5 with cyt-c, cyt-c3 and cyt-f revealed that all the Raman lines are mainly due to the porphyrin skeleton although the vibrational coupling between peripheral substituents and the ring skeleton causes the frequency shift and intensity change of Raman lines. The present results suggest that two ligands of iron in cyt-f may possibly be His (18) and Met (62).
