Bioinorganic Applications of Resonance Raman Spectroscopy

Abstract

This contribution reviews applications of resonance Raman (rR) spectroscopy to the study of heme proteins, explaining how various spectroscopic marker bands reveal key structural features of the buried heme, including oxidation and spin state, as well as the disposition of various peripheral substituents of the heme in its interaction with active site molecular fragments. In addition, it is shown how the technique can provide detailed information about the status of endogenous and exogenous ligands bound to the heme iron, the former including amino acid residues such as histidyl imidazole or the thiolate fragment of cysteine, while the latter often involves the dioxygen molecule bound to various oxidative heme enzymes or the FeCO fragment of the CO adducts of heme proteins, which is a useful probe of the distal pocket environment. Finally, it is also shown how special innovative approaches using pulsed lasers, rapid mixing devices and even cryoradiolytic methods can be employed to reveal detailed structures of otherwise elusive enzymatic intermediates.