Molteni E, Onida G, Tiana G
†Department of Physics, Università degli Studi di Milano, via Celoria 16, 20133 Milano, Italy.
‡INFN, sezione di Milano, via Celoria 16, 20133 Milano, Italy.
J Phys Chem B. 2015 Apr 9;119(14):4803-11. doi: 10.1021/jp5118568. Epub 2015 Mar 27.
We study the conformational dependence of circular dichroism (CD) spectra of amino acid molecules by means of an efficient ab initio DFT approach which is free from the typical gauge invariance issues arising with the use of localized basis sets and/or real-space grids. We analyze the dependence of the chiroptical spectra on the backbone dihedrals in the specific case of alanine and consider the role of side chain degrees of freedom at the examples of leucine, phenylalanine, and serine, whose side chains have different physicochemical properties. The results allow one to identify the most diagnostic regions of the CD spectra and to critically compare the conformations which match the experimental CD data with conformations extracted from the rotamer library. The inclusion of a solvation shell of explicit water molecules and its effect on the CD spectrum are analyzed at the example of alanine.
我们通过一种高效的从头算密度泛函理论（DFT）方法研究氨基酸分子圆二色性（CD）光谱的构象依赖性，该方法不存在使用定域基组和/或实空间网格时出现的典型规范不变性问题。我们分析了在丙氨酸的特定情况下，手性光谱对主链二面角的依赖性，并以亮氨酸、苯丙氨酸和丝氨酸为例考虑侧链自由度的作用，这些氨基酸的侧链具有不同的物理化学性质。结果使人们能够识别CD光谱中最具诊断性的区域，并严格比较与实验CD数据匹配的构象与从旋转异构体库中提取的构象。以丙氨酸为例，分析了包含明确水分子的溶剂化壳及其对CD光谱的影响。
