Resonance Raman applications in investigations of cytochrome c oxidase

Recent applications of resonance Raman (RR) spectroscopy in investigations of cytochrome c oxidase (CcO) are reviewed. Red-excited RR spectra for the fully oxidized "as-isolated" CcO tuned to the ligand-to-metal charge transfer absorption band at 655 nm exhibit a Raman band at 755 cm(-1) assignable to the nu(oo) stretching mode of a peroxide. Binding of CN- diminishes the RR band concomitant with the loss of the charge transfer absorption band. This suggests that a peroxide forms a bridge between heme a(3) and Cu-B. Time-resolved RR spectroscopy of whole mitochondria identified a band at 571 cm(-1) arising from the oxygenated intermediate at Delta t = 0.4,0.6 and 1.4 ms. Bands at 804 and 780 cm(-1) of the P and F intermediates were observed at Delta t = 0.6 and 1.4 ms, respectively. The coordination geometries of the three intermediates are essentially the same as the respective species observed for solubilized CcO. However, the lifetime of the oxygenated intermediate in mitochondria was significantly longer than the lifetime of this intermediate determined for solubilized CcO. This phenomenon is due either to the pH effect of mitochondrial matrix, the effect of Delta pH and/or Delta psi across the membrane, or the effect of interactions with other membrane components and/or phospholipids. This article is part of a Special Issue entitled: Respiratory Oxidases. (C) 2011 Elsevier B.V. All rights reserved.