ヘム蛋白質の赤外分光法による研究

概要

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Potential usefullness of infrared spectroscopy to direct measurement of the ligand binding to hemoprotein is discussed, refereing to CO and CN- binding. CO myoglobin has an asynmetric C-O stretch band which is decomvoluted into 4 symmetrical Gausian curves. The intensy of these decomvoluted bands depends on pH and temperature without any change in band position and half band width, indicating that myoglobin has 4 discrete and rapidly interconvertible conformers. Therefore, X-ray crystallographic structure is regarded as an average of the tertially sturucture of the two dominant conformers which give about 90% of the intergrated area of the experimental curve. C-N stretch bands of cytochrome oxidase cyanide show that cyanide binds only to Cu2+ at fully oxidized state, not to Fe3+ in the O2 binding site, but it does to both Fe and Cu at any oxidation state other than fully oxidized state. The infrared parameters of CN- bound to one metal is quite insensitive to the oxidation state and the ligand binding of the other metal. These are highly unique information about the structure and function of the ligand binding sites, which only infrared spectroscopy can proVide at present.
日本生物物理学会の論文