NMR Relaxation Study of the Bacteriochlorophyll c in Solutions
NMR Relaxation Study of the Bacteriochlorophyll c in Solutions
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DOI：
10.1021/jp040422l
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发表时间：
2004-08
影响因子：
3.3
通讯作者：
Zheng‐Yu Wang;Tomoyuki Kadota;Masayuki Kobayashi;A. Kasuya;T. Nozawa
中科院分区：
文献类型：
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作者：
Zheng‐Yu Wang;Tomoyuki Kadota;Masayuki Kobayashi;A. Kasuya;T. Nozawa
细菌叶绿素（BChl）c是绿色光合细菌中的一个主要捕光色素家族。在有机溶剂中，色素分子能够形成稳定的二聚体并自组装成高聚集体，其已被用作天然叶绿体天线的模型。测量了完整的法呢基（31 R）-[E，E]BChl c F在甲醇、丙酮和四氯化碳中的NMR弛豫时间.在BChlc以单体形式存在的甲醇和丙酮中，大环质子和法尼基质子的自旋-晶格弛豫时间分别为0.3- 1.2s和0.73- 3.3s. BChl c和溶剂分子之间的强氢键导致靠近氢键位点的质子的自旋-自旋弛豫时间（T2 H）显著降低。这一结果可以解释在标量耦合与羟基质子和偶极相互作用与溶剂分子的组合效果。四氯化碳中BChlc二聚体的形成导致T1 H增加，T2 H相对于单体的值大幅度降低，表明由于分子运动大大减少，相关时间变长.使用高度随机的13 C标记的样品，我们能够测量13 C弛豫时间。在甲醇中的大环碳的T1被确定在0.26-3.3 s的范围内，并且这些值随着BChlc形成二聚体而降低，但保持在相同的数量级。（3 1 R）-[E，E] BCHlcF是研究二聚体中氢键性质和分子间动态交换行为的理想分子。
Bacteriochlorophyll (BChl) c is a major light-harvesting pigment family in green photosynthetic bacteria. In organic solvents, the pigment molecules are capable of forming stable dimers and self-assembling into high aggregates which have been used as a model for the native chlorosome antenna. NMR relaxation times were measured for the intact farnesyl (3 1 R)-[E, E]BChl c F in methanol, acetone, and carbon tetrachloride. The spin-lattice relaxation times (T 1 H ) were determined to be 0.3-1.2 s for the macrocyclic protons and 0.73-3.3 s for the farnesyl protons in methanol and acetone in which the BChl c exists as a monomer. Strong hydrogen bonding between the BChl c and solvent molecules resulted in a significant reduction in the spin-spin relaxation times (T 2 H ) for the protons close to the hydrogen-bonding sites. This result can be interpreted in terms of a combined effect of scalar coupling with the hydroxyl proton and dipolar interaction with the solvent molecules. Formation of BChl c dimer in carbon tetrachloride led to an increase in T 1 H and a large decrease in T 2 H with respect to the values of monomer, indicating that the correlation time became longer as a result of the much reduced molecular motion. With the use of a highly randomly 1 3 C-labeled sample, we were able to measure the 1 3 C relaxation times. The T 1 were determined in a range of 0.26-3.3 s for the macrocyclic carbons in methanol, and these values decreased as BChl c formed a dimer but remained in the same order of magnitude. The (3 1 R)-[E, E]BCHl c F is demonstrated as an ideal molecule for studying the hydrogen-bonding property and the dynamic exchange behavior between the individual molecules within a dimer.