Dipole interaction model predicted pi-pi* circular dichroism of cyclo(L-Pro)3 using structures created by semi-empirical, ab initio, and molecular mechanics methods.
Dipole interaction model predicted pi-pi* circular dichroism of cyclo(L-Pro)3 using structures created by semi-empirical, ab initio, and molecular mechanics methods.
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偶极相互作用模型使用半经验、从头计算和分子力学方法创建的结构预测了 cyclo(L-Pro)3 的 pi-pi* 圆二色性。
DOI：
10.1034/j.1399-3011.2003.00046.x
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发表时间：
2003
期刊：
影响因子：
--
通讯作者：
Pierce,KS
中科院分区：
文献类型：
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作者：
Lowe,SL;Pandey,RR;Czlapinski,J;Kie-Adams,G;Hoffmann,MR;Thomasson,KA;Pierce,KS
Cyclo(l-Pro)3(CP3) 是一种合成肽，用于模拟顺式和扭转应变的肽键，还表现出强烈独特的紫外圆二色性 (CD) 光谱。使用肽各种构象的偶极相互作用模型计算酰胺 π − π* 跃迁的圆二色光谱。 CP3 的构象最初是根据晶体数据创建的，然后使用 cvff 力场通过分子力学实现能量最小化；研究了半经验和从头算量子力学额外几何优化的效果。使用各种不同的参数计算每个构象的圆二色光谱，并将每个结果与已发表的实验光谱进行比较 [Deber, C.M., Scatturin, A., Vaidya, V.M. & Blot, E.R. (1970) 小环脯氨酸肽：紫外吸收和 CD。见：肽：化学与生物化学，第一届美国肽研讨会论文集（Weinstein，B.，编辑），Marcel Dekker，纽约，第 163-173 页]。在此，两种不同的构象，即 C3 对称形式和不对称形式，给出的 CD 预测分别与实验光谱不同。在不同的理论层面上预测了能量差异，包括 MP2 和密度泛函理论。当每个构象的预测 CD 谱乘以使用 AM1 优化确定的形成热创建的玻尔兹曼加权因子时，创建的加权复合 CD 谱确实类似于 π − π* 转变的实验，表明两种构象可能同时存在于溶液中。
Cyclo(l‐Pro)3(CP3) is a synthetic peptide created to modelcisand torsionally strained peptide bonds that also exhibits a strong distinctive UV circular dichroic (CD) spectrum. Circular dichroic spectra were computed for the amide π − π* transition using the dipole interaction model for various conformations of the peptide. Conformations of CP3 were created initially from crystal data, and followed by energy minimizations via molecular mechanics using the cvff force field; the effects of additional geometric optimizations by semi‐empirical and ab initio quantum mechanics were investigated. The CD spectra for each conformation were calculated using a variety of different parameters, and each result was compared with the published experimental spectrum [Deber, C.M., Scatturin, A., Vaidya, V.M. & Blout, E.R. (1970) Small cyclic proline peptides: UV absorption and CD. In:Peptides: Chemistry and Biochemistry, Proceedings of the First American Peptide Symposium(Weinstein, B., ed.), Marcel Dekker, New York pp. 163–173]. Herein, two distinct conformations, a C3symmetric and an asymmetric form, gave CD predictions that separately did not resemble the experimental spectrum. Energy differences were predicted at various theoretical levels, including MP2 and density functional theory. When the predicted CD spectra for each conformation were multiplied by Boltzmann weighting factors created using heats of formation determined by the AM1 optimizations, the weighted composite CD spectrum created did resemble experiment for the π − π* transition indicating that both conformations may exist simultaneously in solution.