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Vibrational infrared and Raman spectra of polypeptides: Fragments-in-fragments within molecular tailoring approach

机译:多肽的振动红外光谱和拉曼光谱:分子剪裁方法中的片段碎片

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摘要

The present work reports the calculation of vibrational infrared (IR) and Raman spectra of large molecular systems employing molecular tailoring approach (MTA). Further, it extends the grafting procedure for the accurate evaluation of IR and Raman spectra of large molecular systems, employing a new methodology termed as Fragments-in-Fragments (FIF), within MTA. Unlike the previous MTA-based studies, the accurate estimation of the requisite molecular properties is achieved without performing any full calculations (FC). The basic idea of the grafting procedure is implemented by invoking the nearly basis-set-independent nature of the MTA-based error vis--vis the respective FCs. FIF has been tested out for the estimation of the above molecular properties for three isomers, viz., beta-strand, 3(10)- and alpha-helix of acetyl(alanine)(n)NH2 (n = 10, 15) polypeptides, three conformers of doubly protonated gramicidin S decapeptide and trpzip2 protein (PDB id: 1LE1), respectively, employing BP86/TZVP, M06/6-311G**, and M05-2X/6-31G** levels of theory. For most of the cases, a maximum difference of 3 cm(-1) is achieved between the grafted-MTA frequencies and the corresponding FC values. Further, a comparison of the BP86/TZVP level IR and Raman spectra of a-helical (alanine)(20) and its N-deuterated derivative shows an excellent agreement with the existing experimental spectra. In view of the requirement of only MTA-based calculations and the ability of FIF to work at any level of theory, the current methodology provides a cost-effective solution for obtaining accurate spectra of large molecular systems. (C) 2016 AIP Publishing LLC.
机译:本工作报告了使用分子定制方法(MTA)计算大分子系统的振动红外(IR)和拉曼光谱。此外,它还采用了一种新的方法,在MTA内采用了称为“片段中的片段(FIF)”的方法,扩展了接枝程序,以准确评估大分子系统的IR和拉曼光谱。与以前的基于MTA的研究不同,无需进行任何完整的计算(FC)就可以准确估算所需的分子性质。嫁接程序的基本思想是通过针对各个FC调用基于MTA的错误的几乎与基集无关的特性来实现的。已测试FIF来评估乙酰基(丙氨酸)(n)NH2(n = 10、15)多肽的三种异构体的上述分子特性,即β-链,3(10)-和α-螺旋,分别采用BP86 / TZVP,M06 / 6-311G **和M05-2X / 6-31G **的理论水平,分别构建了三个质子化的双倍质子化的短杆菌肽S十肽和trpzip2蛋白(PDB ID:1LE1)。对于大多数情况,MTA嫁接的频率与相应的FC值之间的最大差为3 cm(-1)。此外,对α-螺旋(丙氨酸)(20)及其N氘代衍生物的BP86 / TZVP能级IR和拉曼光谱的比较显示出与现有的实验光谱极好的一致性。考虑到仅需要基于MTA的计算以及FIF可以在任何理论水平上运行的能力,当前的方法学均提供了一种经济高效的解决方案,可获取大分子系统的准确光谱。 (C)2016 AIP出版有限责任公司。

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