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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 23, Number 12
BKCSDE 23(12)
December 20, 2002 

14 N Mims Pulsed-ENDOR of Proximal Histidine and Heme of Aquometmyoglobin and Fluorometmyoglobin
Hong-In Lee
Metmyoglobin, ENDOR, Mims ENDOR, 14N hyperfine, High-spin Fe(III)
Previous 19F and 1,2H electron-nuclear double resonance (ENDOR) study of fluorometmyoglobin (MbF) in frozen-solution state provided sensitive tools sensing subtle structural changes of the heme that are not obtainable from X-ray. [Fann et al., J. Am. Chem. Soc. 1995, 117, 6019] Because of the intrinsic inhomo-geneouse EPR line broadening effect of MbF in frozen-solution state, detection of the electronic and geometrical changes of the heme ring itself and the proximal histidine by using 14N CW ENDOR was interfered. In the present study, hyperfine-sensitive 14N Mims ENDOR technique of pulsed-EPR was employed to probe the changes. With two different τvalues of 128 and 196 ns, 14N ENDOR signals of the heme and proximal histidine were completely resolved at g' (= ge = 2). This study presents that X-band 14N Mims ENDOR sequence can sensitively detect the small changes of the spin densities and p orbital populations of the proximal and the heme nitrogens, caused by ligand and pH variation of the distal site.
1769 - 1772
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