Resonance Raman detection of Fe-CO stretching and Fe-C-O bending vibrations in sterically hindered carbonmonoxy "strapped hemes". A structural probe of Fe-C-O distortion.
Resonance Raman detection of Fe-CO stretching and Fe-C-O bending vibrations in sterically hindered carbonmonoxy "strapped hemes". A structural probe of Fe-C-O distortion.
复制标题
位阻碳单氧“束缚血红素”中 Fe-CO 拉伸和 Fe-C-O 弯曲振动的共振拉曼检测。
DOI：
10.1021/bi00288a028
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发表时间：
1983
期刊：
影响因子：
2.9
通讯作者：
Chang,CK
中科院分区：
文献类型：
--
作者：
Yu,NT;Kerr,EA;Ward,B;Chang,CK
Nai-Teng Yu，* Ellen A. Kerr，Brian Ward，and C. K. Chang* 摘要：我们报道了空间位阻血红素-CO复合物中Fe-C-0畸变的共振拉曼研究。空间位阻由绑在血红素一面上的烃链提供。发现降低CO结合亲和力的空间位阻增加（通过减小链长）会增加Fe-CO伸缩频率：血红素5（未束缚的），495 cm-1; FeSP-15，509 cm-1; FeSP-14，512 cm-1; FeSP-13，514 cm-1。这可以解释为CO有效质量的减少和CO的C原子与吡咯环的N原子之间的相互作用的增加。Soret激发时Fe-C-O弯曲模的共振拉曼增强可能与CO配体倾斜时卟啉（ir*）和CO（ir*）轨道之间的重叠相关。它的强度相对于Fe-CO伸缩模式的增加，在这些“束缚血红素”的空间位阻。此外，我们估计了Fe-CO角的同位素数据在各种血红素-CO复合物。据推测，该角度为167±5（FeSP-15）和175±5（FeSP-14，FeSP-13，Mb-CO和Hb-CO）。血红素蛋白中远端残基的空间位阻在调节血红素对t的反应性中起重要作用。来自化学学院，格鲁吉亚理工学院，亚特兰大，格鲁吉亚30332（N.- TY和EAK）和密歇根州立大学化学系，东兰辛，密歇根48824（BW和CKC）。1983年1月4日收到。这项工作得到了美国国立卫生研究院资助GM 18894和国家科学基金会资助CHE-8210200的支持。CKC是阿尔弗雷德P斯隆研究员（1980-1984）和卡米尔亨利德雷福斯教师学者（1980-1985）。不同的配体（Moffat等人，1970，以及其中引用的参考文献; Szabo，1978）。生物氧载体如血红蛋白（Hb）和肌红蛋白（Mb）的血红素袋具有以其自然弯曲的端部构型配合双氧（O2）的几何形状（Coliman等人，一九七四年;菲利普斯，1978，1980; Shaanan，1982），但不是一氧化碳（CO）分子，它优先以线性和垂直的方式与铁结合（Hoard，1975; Peng & Ibers，1976）。已经提出，远端空间效应降低了亲合性，
Nai-Teng Yu,* Ellen A. Kerr, Brian Ward, and C. K. Chang* abstract: We report resonance Raman studies of the Fe-C-0 distortion in sterically hindered heme-CO complexes. The steric hindrance is provided by a hydrocarbon chain strapped across one face of the heme. Increasing the steric hindrance (by decreasing the chain length), which reduces the CO binding affinity, is found to increase the Fe-CO stretching frequencies: heme 5 (unstrapped), 495 cm-1; FeSP-15, 509 cm™ 1; FeSP-14, 512 cm™ 1; FeSP-13, 514 cm™ 1. This is interpreted in terms of a decrease in the CO effective mass and increased interactions between the C atom of CO and the N atom (s) of the pyrrole ring (s). Resonance Raman enhancement of the Fe-C-0 bending mode upon Soret excitation may be correlated with the overlap between the porphyrin (ir*) and CO (ir*) orbitals when the CO ligand is tilted. Its intensity relative to that of the Fe-CO stretching modeincreases with increasing steric hindrance in these “strapped hemes”. In addition, we have estimated the Fe-CO angles from isotope data in various heme-CO complexes. It is inferred that the angles are 167±5 (FeSP-15) and 175±5 (FeSP-14, FeSP-13, Mb-CO, and Hb-CO). e steric hindrance by distal residues in hemoproteins plays an important role in the regulation of heme reactivity toward tFrom the School of Chemistry, Georgia Institute of Technology, Atlanta, Georgia 30332 (N.-TY and EAK), and the Department of Chemistry, Michigan State University, East Lansing, Michigan 48824 (BW and CKC). Received January 4, 1983. This work was supported by National Institutes of Health Grant GM 18894 and National Science Foundation Grant CHE-8210200. CKC is an Alfred P. Sloan Fellow (1980-1984) and a Camile Henry Dreyfus Teacher-Scholar (1980-1985). different ligands (Moffat et al., 1970, and references cited therein; Szabo, 1978). The heme pockets of biological oxygen carriers such as hemoglobins (Hb) and myoglobins (Mb) have a geometry that fits dioxygen (02) in its natural bent, end-on configuration (Coliman et al., 1974; Phillips, 1978, 1980; Shaanan, 1982) but not a carbon monoxide (CO) molecule, which preferentially bindsto the iron in a linear and perpen-dicular fashion (Hoard, 1975; Peng & Ibers, 1976). It has been proposed that the distal steric effect lowers the affinity