Wang J, Takahashi S, Rousseau D L
AT&T Bell Laboratories, Murray Hill, NJ 07974, USA.
Proc Natl Acad Sci U S A. 1995 Sep 26;92(20):9402-6. doi: 10.1073/pnas.92.20.9402.
Two CO-isotope sensitive lines have been detected in the overtone region of the resonance Raman spectra of CO-bound hemeproteins. One line is assigned as the overtone of the Fe-CO stretching mode and is located in the 1000- to 1070-cm-1 region. The other line is found in the 1180- to 1210-cm-1 region and is assigned as a combination between a porphyrin mode, nu 7, and the Fe-CO stretching mode. The high intensities of these lines, which in the terminal oxidase class of proteins are of the same order as those of the fundamental stretching mode, indicate that the mechanism of enhancement for modes involving the Fe-CO moiety is different from that for the modes of the porphyrin macrocycle and call for reexamination of Raman theory of porphyrins as applied to axial ligands. The anharmonicity of the electronic potential function was evaluated, revealing that in the terminal oxidases the anharmonicity is greater than in the other heme proteins that were examined, suggesting a distinctive interaction of the bound CO with its distal environment in this family. Furthermore, the anharmonicity correlates with the frequency of the C-O stretching mode, demonstrating that both of these parameters are sensitive to the Fe-CO bond energy. The overtone and combination lines involving the bound CO promise to be additional probes of heme protein structural properties.
在与一氧化碳结合的血红素蛋白的共振拉曼光谱的泛音区域中检测到两条对一氧化碳同位素敏感的谱线。一条谱线被指定为铁-一氧化碳伸缩模式的泛音，位于1000至1070厘米-1区域。另一条谱线出现在1180至1210厘米-1区域，被指定为卟啉模式ν7与铁-一氧化碳伸缩模式之间的组合。这些谱线的高强度，在蛋白质的末端氧化酶类别中与基本伸缩模式的强度处于同一量级，表明涉及铁-一氧化碳部分的模式的增强机制与卟啉大环模式的增强机制不同，这就需要重新审视应用于轴向配体的卟啉拉曼理论。评估了电子势函数的非谐性，结果表明在末端氧化酶中，非谐性大于所研究的其他血红素蛋白，这表明该家族中结合的一氧化碳与其远端环境存在独特的相互作用。此外，非谐性与碳-氧伸缩模式的频率相关，表明这两个参数都对铁-一氧化碳键能敏感。涉及结合的一氧化碳的泛音和组合谱线有望成为血红素蛋白结构性质的额外探针。
