SOLVENT DEPENDENCE OF PYRIMIDINE DIMER SPLITTING IN A COVALENTLY LINKED DIMER-INDOLE SYSTEM
SOLVENT DEPENDENCE OF PYRIMIDINE DIMER SPLITTING IN A COVALENTLY LINKED DIMER-INDOLE SYSTEM
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DOI：
10.1111/j.1751-1097.1990.tb08683.x
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发表时间：
1990-10-01
影响因子：
3.3
通讯作者：
ROSE, SD
中科院分区：
文献类型：
--
作者：
KIM, ST;HARTMAN, RF;ROSE, SD
环丁二嘧啶（嘧啶二聚体）经历被吲哚衍生物光敏化的分裂。我们已经制备了一种化合物，其中两个碳连接体将二聚体连接到吲哚基。吲哚基荧光猝灭表明分子的两个部分在激发态相互作用。二聚体分裂的分子内光敏化显著地依赖于溶剂，范围从水中的Φ spl = 0.06到所检测的最小极性溶剂混合物1，4-二氧杂环己烷-异戊烷（5：95）中的Φ spl = 0.41的高值。在吲哚环上具有5-甲氧基取代基的衍生物表现类似。这些结果已被解释在电子转移从激发吲哚基团的二聚体，这将产生一个电荷分离的物种。这种物质中的二聚体阴离子可以分裂或进行反向电子转移。背电子转移是在马库斯反转区的可能性，可以用来合理化所观察到的溶剂依赖性分裂。在反转区域中，电荷复合的高驱动力超过溶剂的重组能，低极性溶剂的重组能小于高极性溶剂的重组能。如果这一理论适用于假设的电荷分离的物种，则在较低极性的溶剂中，将预期较慢的背电子转移，并且因此较高的分裂效率。光裂解酶可能已经进化，其中低极性活性位点阻碍电子的反向转移，从而有助于酶促二聚体裂解的效率。
Cyclobutadipyrimidines (pyrimidine dimers) undergo splitting that is photosensitized by indole derivatives. We have prepared a compound in which a two-carbon linker connects a dimer to an indolyl group. Indolyl fluorescence quenching indicated that the two portions of the molecule interact in the excited state. Intramolecular photosensitization of dimer splitting was remarkably solvent dependent, ranging from .PHI.spl = 0.06 in water to a high value of .PHI.spl = 0.41 in the least polar solvent mixture examined, 1,4-dioxane-isopentane(5:95). A derivative with a 5-methoxy substituent on the indolyl ring behaved similarly. These results have been interpreted in terms of electron transfer from the excited indolyl group to the dimer, which would produce a charge-separated species. The dimer anion within such a species could split or undergo back electron transfer. The possibility that back electron transfer is in the Marcus inverted region can be used to rationalize the observed solvent dependence of splitting. In the inverted region, the high driving force of a charge recombination exceeds the reorganization energy of the solvent, which is less for solvents of low polarity than those of high polarity. If this theory is applicable to the hypothetical charge-separated species, a slower back electron transfer, and consequently higher splitting efficiencies, would be expected in solvents of lower polarity. Photolyases may have evolved in which a low polarity active site retards back transfer of an electron and thereby contributes to the efficiency of the enzymatic dimer splitting.