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首页> 外文期刊>Chemistry: A European journal >Assignment of Vibrational Circular Dichroism Cross-Referenced Electronic Circular Dichroism Spectra of Flexible Foldamer Building Blocks: Towards Assigning Pure Chiroptical Properties of Foldamers
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Assignment of Vibrational Circular Dichroism Cross-Referenced Electronic Circular Dichroism Spectra of Flexible Foldamer Building Blocks: Towards Assigning Pure Chiroptical Properties of Foldamers

机译：振动圆形二色性的分配交叉引用的柔性卷曲基层构建块的电子圆形二色二色二分谱：用于分配绒毛膜的纯粹性毛细防产

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Assignment of the most established electronic circular dichroism (ECD) spectra of polypeptides and foldamers is either "evidence based" or relies on the 3D structures of longer oligomers of limited internal dynamics, which are derived from NMR spectroscopy (or X-ray) data. Critics warn that the use of NMR spectroscopy and ECD side by side has severe limitations for flexible molecules because explicit knowledge of conformational ensembles is a challenge. Herein, an old-new method of comparing ab initio computed and measured vibrational circular dichroism (VCD) data is presented to validate both the structures (conf(i)) and their relative weights (c(i)) that make up the conformational ensemble. Based on the array of {conf(i), c(i)}, the pure ECD spectra, g(i)conf(i), can be ab initio calculated. The reconstructed spectrum Sc(i)g(i)~(conf(i)) can thus help to assign any experimental ECD counterparts. Herein, such a protocol is successfully applied to flexible foldamer building blocks of sugar bamino acid diamides. The epimeric pair of the model system was selected because these molecules were conformationally tunable by simple chemical modification, and thus, the robustness of the current approach could be probed. The initial hydrogen bond (NH···O) eliminated by N-methylation reorients the amide plain, which influences the chiroptical properties of the foldamer building block; this structural change is successfully monitored by changes to the VCD and ECD transitions, which are now assigned to pure conformers. The current method seems to be general and effective without requiring extensive CPU and spectroscopic resources.
机译：多肽和糊涂虫的最既已建立的电子圆形二中型（ECD）光谱的分配是“基于证据”，或者依赖于有限内部动态的较长低聚物的3D结构，其衍生自NMR光谱（或X射线）数据。批评者警告说，使用NMR光谱和ECD并排的柔性分子的严重限制，因为明确的构象集合是一项挑战。这里，提出了一种比较AB Initio计算和测量的振动圆形二色（VCD）数据的旧方法以验证构成构象集合的结构（CONF（I））及其相对权重（C（i）） 。基于{conf（i），c（i）}的阵列，纯的ECD谱图，G（i）conf（i）可以计算到AB Initio。因此，重建的频谱Sc（i）〜（conf（i））因此可以有助于分配任何实验的ECD对应物。这里，这种方案成功地应用于糖Bamina酰胺酰胺的柔性卷曲物构件块。选择模型系统的映射对，因为这些分子通过简单的化学修饰进行了一致可调谐，因此可以探测目前方法的鲁棒性。通过N-甲基化重塑酰胺普通消除的初始氢键（NH··o），其影响卷曲物构件块的含毛细管性能;通过对VCD和ECD转换的更改成功监控该结构变化，这些转换现在分配给纯整体器。目前的方法似乎是一般性的并且有效而不需要广泛的CPU和光谱资源。

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