Probing the structure and Franck–Condon region of protochlorophyllide a through analysis of the Raman and resonance Raman spectra
Probing the structure and Franck–Condon region of protochlorophyllide a through analysis of the Raman and resonance Raman spectra
复制标题
通过拉曼和共振拉曼光谱分析探讨原叶绿素 a 的结构和 Franck-Condon 区域
DOI：
10.1002/jrs.2458
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发表时间：
2009
影响因子：
2.5
通讯作者：
J. Popp
中科院分区：
文献类型：
--
作者：
R. Hanf;S. Tschierlei;B. Dietzek;S. Seidel;G. Hermann;M. Schmitt;J. Popp
利用拉曼光谱和共振拉曼光谱研究了光调控酶原叶绿素氧化还原酶(POR)底物原叶绿素a的结构和Franck-codon区。将光谱结果与结构密切相关的八乙基卟啉镁模型化合物的光谱进行了比较，并用密度泛函理论(DFT)计算对其进行了解释。结果表明，两个大环的电子性质受到不同振动耦合模式的影响，导致原叶绿素a在可见光区有较高的吸收截面。此外，比较了原叶绿素a的傅里叶变换(FT)-拉曼光谱和RR光谱，指出了激发时共振增强的模式。根据振动简正模计算，这些模式包括大环的CC环呼吸和CC伸缩振动。特别是，在1703 cm−1处的强带可归因于环戊酮环的CO羰基振动，该环以共轭方式连接到卟啉环系的π电子路径上。根据提出的原叶绿素a在POR中的光还原反应模型，讨论了该模式对电子共振激发的增强作用。版权所有©2009 John Wiley&Sons，Ltd.
The structure and Franck–Condon region of protochlorophyllide a, a precursor in the biosynthesis of chlorophyll and substrate of the light-regulated enzyme protochlorophyllide oxidoreductase (POR), were investigated by Raman and resonance Raman (RR) spectroscopy. The spectroscopic results are compared to the spectra of the structurally closely related porphyrin model compound magnesium octaethylporphyrin (MgOEP), and interpreted on the basis of density functional theory (DFT) calculations. It is shown that the electronic properties of the two porphyrin macrocycles are affected by different vibrational coupling modes, resulting in a higher absorption cross section of protochlorophyllide a in the visible spectral region. Furthermore, a comparison of the Fourier transform (FT)-Raman and RR spectra of protochlorophyllide a indicates the modes that are resonantly enhanced upon excitation. Based on vibrational normal mode calculations, these modes include CC ring-breathing and CC stretching vibrations of the porphyrin macrocycle. In particular, the strong band at 1703 cm−1 can be attributed to the CO carbonyl vibration of the cyclopentanone ring, which is attached in conjugation to the π-electron path of the porphyrin ring system. The enhancement of that mode upon electronically resonant excitation is discussed in the light of the reaction model suggested for the photoreduction of protochlorophyllide a in the POR. Copyright © 2009 John Wiley & Sons, Ltd.