Abstract
Vibrational changes associated with CO recombination to ferrous horseradish peroxidase were investigated by rapid-scan FTIR (Fourier-transform IR) spectroscopy in the 1200–2200 cm−1 range. At pH 6.0, two conformers of bound CO are present that appear as negative bands at 1905 and 1934 cm−1 in photolysis spectra. Their recombination rate constants are identical, confirming that they arise from two substates of bound CO that are in rapid thermal equilibrium, rather than from heterogeneous protein sites. A smaller positive band at 2134 cm−1 also appears on photolysis and decays with the same rate constant, indicative of an intraprotein geminate site involved in recombination or, possibly, a weak-affinity surface CO-binding site. Other signals arising from protein and haem in the 1700–1200 cm−1 range can also be time-resolved with similar kinetics.
- carbon monoxide
- Fourier-transform infrared spectroscopy (FTIR spectroscopy)
- horseradish peroxidase
- rapid-scan
- time-resolved spectroscopy
Footnotes
Transition Metals in Biochemistry: A joint Biochemical Society meeting with the Inorganic Biochemistry Discussion Group to honour Professor Andrew Thomson FRS, held at University of East Anglia, Norwich, U.K., 24–26 June 2008. Organized and Edited by Steve Chapman (Edinburgh, U.K.), David Richardson (University of East Anglia, U.K.) and Nick Watmough (University of East Anglia, U.K.).
Abbreviations: FTIR, Fourier-transform IR; HRPC, horseradish peroxidase isoenzyme C
- © The Authors Journal compilation © 2008 Biochemical Society