A Raman study on the C(4)=O stretching mode of flavins in flavoenzymes: hydrogen bonding at the C(4)=O moiety.
A Raman study on the C(4)=O stretching mode of flavins in flavoenzymes: hydrogen bonding at the C(4)=O moiety.
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黄素酶中黄素C(4)=O伸缩模式的拉曼研究：C(4)=O部分的氢键。
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发表时间：
1997
期刊：
影响因子：
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通讯作者：
K. Shiga
中科院分区：
文献类型：
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作者：
I. Hazekawa;Y. Nishina;K. Sato;M. Shichiri;R. Miura;K. Shiga
用拉曼光谱研究了一系列黄素和黄蛋白中异alloxazine核C(4)=O部分的氢键。拉曼带的同位素效应证实了在1710 cm（-1）附近观测到的拉曼带主要来源于C(4)=O的伸缩振动模式。在C(4)=O的拉伸频率和13C(4)的化学位移之间观察到线性相关，这表明拉曼光谱和核磁共振光谱的数据反映了一种共同的扰动，即氢键。黄素和黄素蛋白之间C(4)= 0频率的最大差异为36 cm(-1)[核黄素结合蛋白为1723 cm(-1)] (Kim， M. and Carey， P.C. (1993)；化学。中链酰基-辅酶a脱氢酶与乙酰乙酰基-辅酶a络合物的Soc. 115, 7015-7016)和1,687 cm(-1)；在C(4)= 0时，黄酮类蛋白之间的氢键强度差异最大，为40 ~ 70 kJ/mol。利用C=O拉伸频率与C=O键长之间的经验线性相关性，估计在这里处理的黄蛋白之间键长的最大差异约为0.017 A。中链和短链酰基辅酶a脱氢酶在C(4)= 0处的氢键在与底物类似物络合后变得更强。由于C(4)=O处的氢键有望增强N(5)位置的电子接受能力，因此底物结合本身可能通过增强氢键来提高黄素的反应性。
Raman spectroscopy was used to investigate the hydrogen bonding at the C(4)=O moiety of the isoalloxazine nucleus in a series of flavins and flavoproteins. Isotope effects of Raman bands confirmed that the band observed around 1,710 cm(-1) is mainly derived from C(4)=O stretching vibrational mode. A linear correlation was observed between the frequency of C(4)=O stretching and the chemical shift of 13C(4), suggesting that the data from both Raman and NMR spectroscopies reflect a common perturbation, i.e., hydrogen bonding. The maximum difference of C(4)=O frequency among flavins and flavoproteins examined is 36 cm(-1) [1,723 cm(-1) for riboflavin-binding protein (Kim, M. and Carey, P.C. (1993) J. Am. Chem. Soc. 115, 7015-7016) and 1,687 cm(-1) for the complex of medium-chain acyl-CoA dehydrogenase with acetoacetyl-CoA]; the maximum difference of 40-70 kJ/mol in the hydrogen bonding strength at the C(4)=O exists among flavoproteins. By use of an empirical linear correlation between the frequency of C=O stretching and the bond length of the C=O, it is estimated that the maximum difference in the bond length among flavoproteins treated here is ca. 0.017 A. The hydrogen bonding at the C(4)=O in medium-chain and short-chain acyl-CoA dehydrogenases becomes stronger upon complexation with substrate analogs. Since the hydrogen bonding at the C(4)=O is expected to enhance the electron-accepting capacity of the N(5) position, substrate-binding itself probably raises the reactivity of flavin, through enhancing the hydrogen bonding.