DETERMINATION OF THE ORIENTATION OF CARBON MONOXIDE IN THE HEME POCKET OF MYOGLOBIN IN SOLUTION USING TIME-RESOLVED MID-INFRARED SPECTROSCOPY
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Date
1994
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Ohio State University
Abstract
The orientation of carbon monoxide (CO) in the heme pocket of myoglobin (Mb) in ambient temperature been determined by using lime-resolved mid-IR spectroscopy. After photolyzing MbCO with polarized visible pulses, polarized IR pulses were used to monitor the change in the absorbance spectra of CO stretch bands. The ratio of perpendicular and parallel polarized absorbencies is directly related to the angle of the CO dipole with respect to the heme normal. The ratio was found to be near unity, suggesting that the CO is either oriented near the magic angle with respect to heme normal or distributed isotropically. The wavelength-dependent polarization anisotropy resolved this issue; the angle of CO is approximately 62 degrees away from the normal to the heme plane
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Author Institution: Department of Chemistry, Harvard University