RESONANCE RAMAN-SPECTRA OF METHEMOGLOBIN DERIVATIVES - SELECTIVE ENHANCEMENT OF AXIAL LIGAND VIBRATIONS AND LACK OF AN EFFECT OF INOSITOL HEXAPHOSPHATE
RESONANCE RAMAN-SPECTRA OF METHEMOGLOBIN DERIVATIVES - SELECTIVE ENHANCEMENT OF AXIAL LIGAND VIBRATIONS AND LACK OF AN EFFECT OF INOSITOL HEXAPHOSPHATE
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DOI：
10.1021/bi00645a032
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发表时间：
1977-01-01
期刊：
影响因子：
2.9
通讯作者：
SAUER, K
中科院分区：
文献类型：
--
作者：
ASHER, SA;VICKERY, LE;SAUER, K
通过在550-650 nm区域激发，获得高铁血红蛋白[人]的OH-、N3-和F-衍生物的共振拉曼光谱。在N3-、OH-和F-络合物中，分别观察到413和497 cm-1处的峰和471和443 cm-1处的双峰在电荷转移带中随激发的选择性增强。这些峰归属于Fe-轴向配体的伸展，基于：氢氧化物络合物的497 cm-1峰向较低能量的20 cm-1位移，18 OH-对16 OH-的同位素取代; 413 cm-1拉曼峰与先前分配给模型血红素中Fe-N3-伸缩的421 cm-1 IR峰的接近度，叠氮配合物的拉曼光谱和选择性出现的471和443 cm-1峰的F-配合物的拉曼光谱。在F-衍生物中在471和443 cm-1处观察到的双重峰可能反映了由于H2O与α中的F-配体的H-键合而导致的血红素腔中的不均匀性。和β亚基，如先前基于X射线衍射结果所建议的。Fe-F-振动的频率可能反映了Fe从血红素平面的面外畸变。Fe-F-振动频率的偏移的缺乏表明，在添加肌醇六磷酸时，Fe相对于血红素平面几乎没有或没有移动，这被认为改变了高铁血红蛋白的R和T形式之间的变构平衡。这一结果与最近MetHb-F-的IHP复合物的X射线晶体学研究一致。激发分布测量表明，高铁血红蛋白OH-中的电荷转移带与高铁血红蛋白N3-中的电荷转移带一样是z极化的，而在高铁血红蛋白F-中，电荷转移跃迁与α π混合。到. pi. *过渡
Resonance Raman spectra were obtained for the OH-, N3- and F- derivatives of methemoglobin [human] by excitation in the 550-650 nm region. A selective enhancement with excitation in the charge-transfer bands is observed for peaks at 413 and 497 cm-1 and a doublet at 471 and 443 cm-1 in the N3-, OH- and F- complexes, respectively. These peaks are assigned to Fe-axial ligand stretches based on: a 20 cm-1 shift of the 497 cm-1 peak of the hydroxide complex to lower energy on isotopic substitution of 18OH- for 16OH-; the proximity of the 413 cm-1 Raman peak to the 421 cm-1 IR peak previously assigned to the Fe-N3- stretch in a model heme-azide complex and the selective appearance of the 471 and 443 cm-1 peaks in the Raman spectra of the F- complex. The doublet observed at 471 and 443 cm-1 in the F- derivative may reflect a heterogeneity in the heme cavity due to H- bonding of H2O to the F- ligand in the .alpha. and .beta. subunits, as was previously suggested based on X-ray diffraction results. The frequency of the Fe-F- vibration probably reflects the out-of-plane distortion of the Fe from the heme plane. The lack of a shift in frequency of the Fe-F- vibration suggests that there is little or no movement of the Fe with respect to the heme plane on addition of inositol hexaphosphate, which is thought to alter the allosteric equilibrium between the R and T forms of methemoglobin. This result is consistent with a recent X-ray crystallographic study of an IHP complex of MetHb-F-. Excitation profile measurements suggest that the charge-transfer band in methemoglobin OH- like that in methemoglobin N3- is z polarized, while in methemoglobin F- the charge transfer transition is mixed with a .pi. to .pi.* transition.