Dynamic Exchange Properties of the Antiparallel Bacteriochlorophyll c Dimers
Dynamic Exchange Properties of the Antiparallel Bacteriochlorophyll c Dimers
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DOI：
10.1021/jp035124n
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发表时间：
2003-08
影响因子：
3.3
通讯作者：
M. Umetsu;R. Seki;Tomoyuki Kadota;Zheng‐Yu Wang;and Tadafumi Adschiri;T. Nozawa
中科院分区：
文献类型：
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作者：
M. Umetsu;R. Seki;Tomoyuki Kadota;Zheng‐Yu Wang;and Tadafumi Adschiri;T. Nozawa
用二维核磁共振交换谱（EXSY）研究了（31 R）-型细菌叶绿素（BChl）c二聚体的反平行背驮构象的动态交换行为.反平行二聚体中两个BChl c分子之间的交换速率从EXSY光谱中由于化学交换的交叉峰的积分强度进行评估，并且发现其值随着溶剂极性的升高而急剧增加。交换速率与温度的关系可用Arrhenius方程来描述，其参数反映了交换过程中快交换速率与过渡态稳定性的关系。热力学分析也被应用到研究的反平行二聚体的交换速率的取代基的影响。8位取代基的加入使交换速率增加的主要原因是频率因子的增加，而不是活化能的增加。
The dynamic exchange behavior of the (31R)-type bacteriochlorophyll (BChl) c dimer with an antiparallel piggy-back conformation has been investigated by two-dimensional nuclear magnetic resonance exchange spectroscopy (EXSY). The exchange rate between two BChl c molecules in the antiparallel dimer was evaluated from the integrated intensities of cross-peaks due to chemical exchange in the EXSY spectra, and its values were found to dramatically increase with the rise of solvent polarity. The temperature dependence of the exchange rates can be well expressed by the Arrhenius equation, the parameters of which show the correlation of the fast exchange rate with the stability of a transition state in the exchange process. Thermodynamic analysis was also applied to investigate the substituent effect on the exchange rate of the antiparallel dimer. The increase of the exchange rate upon addition of substituents at the peripheral 8-position was mainly attributed to the rise in frequency factor rather than activati...