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The exact structure of an arginine-carboxylate salt bridge in different chemical environments remains a controversial problem.In the present work,the zwitterionic and neutral forms of arginine-carboxylate salt bridge were studied by the B3LYP/6-311G(d,p)//PM3 method.It turns out that the neutral forms are more stable than the zwitterionic coumterparts in gas phase.However,whnen bound by α-cyclodextrin,the zwitterionic forms become more stable than the corresponding neutral ones.It is suggested that the hydrophobic environment provided by the cyclodextrin cavity leads to such behavior.Therefore,the salt bridge still could be in a zwitterionic form in the hydrophobic interior of the real proteins. 相似文献
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通过荧光猝灭实验和测定二聚体裂解程度的辐照实验,研究色氨酸(Trp)及 其二肽色氨酰苯丙氨酸(Trp-Phe)对cis-syn型1,3-二甲基胸腺嘧啶二聚体( DMTD)的光敏化裂解作用。结果表明,色氨酸及其二肽在较强光(λ > 290 nm) 辐照下,主要通过双光子电离生成的光合电子(e_(aq)~-)导致二聚体裂解,其次 ,通过激发单重态与二聚体间的电子转移导致二聚体裂解。另外一导致二聚体裂解 的可能途径:色氨酸残基激发三重态与二聚体间的电子转移光敏化二聚体裂解。 相似文献
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The reduction of benzylidenemalononitrile by 1-benzyl-1,4-dihydronicotinamide undergoes via a one-step hydride transfer mechanism rather than a multistep mechanism involving initial electron transfer. 相似文献
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