Biochimica et Biophysica Acta, 416 (1975) 169-189 © Elsevier Scientific Publishing Company, Amsterdam - Printed in The Netherlands BBA86024 RESONANCE RAMAN SPECTROSCOPIC STUDIES OF HEME PROTEINS THOMAS G. SPIRO Department of Chemistry, Princeton University, Princeton, N. J. 08540 (U.S.A.) (Received January 29th, 1975) CONTENTS 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169 II. Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170 A. Heine electronic spectra . . . . . . . . . . . . . . . . . . . . . . . . . . . 170 B. Resonance Raman scattering . . . . . . . . . . . . . . . . . . . . . . . . . 171 C. Characteristics of heme scattering . . . . . . . . . . . . . . . . . . . . . . . 172 1. Scattering mechanisms . . . . . . . . . . . . . . . . . . . . . . . . . . 172 2. Anomalous polarization . . . . . . . . . . . . . . . . . . . . . . . . . . 173 1II. Structural interpretation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177 A. Nature of the enhanced heine vibrational modes . . . . . . . . . . . . . . . . . 177 B. Assignment of the porphyrin ring modes . . . . . . . . . . . . . . . . . . . . 178 C. Correlations with oxidation and spin states . . . . . . . . . . . . . . . . . . . 180 IV. Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182 A. Cooperativity in 02 binding to Fe and Co hemoglobin .............. 182 B. Hemoglobin quaternary structure . . . . . . . . . . . . . . . . . . . . . . . 184 C. Anomalous heine structures in cytochrome c" and horseradish peroxidase ..... 184 D. Electron distribution in oxy-hemoglobin . . . . . . . . . . . . . . . . . . . . 185 E. Heine components of the mitochondrial electron transport chain ......... 186 V. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187 I. INTRODUCTION Resonance Raman spectra were first reported for hemoglobin [1,2] and cyto- chrome c [3,4] in 1972. (Preliminary Raman data on myoglobin and catalase were reported in 1969 [16].) Since then, resonance Raman studies of heine proteins [5-25] and porphyrins [26-32] have been actively pursued in several laboratories. Consider- able progress has been made in clarifying both the mechanism of resonance Raman scattering, and the structural implications of the spectra. The technique holds much promise for monitoring stuctural features of the heme group. A Raman spectrum is the spectrum of light scattered inelastically from a