Fragment-Molecular-Orbital-Method-Based ab Initio NMR Chemical-Shift Calculations for Large Molecular Systems

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• 作者：Qi Gao ; Satoshi Yokojima ; Dmitri G. Fedorov ; Kazuo Kitaura ; Minoru Sakurai ; Shinichiro Nakamura
• 刊名：Journal of Chemical Theory and Computation
• 出版年：2010
• 出版时间：April 13, 2010
• 年：2010
• 卷：6
• 期：4
• 页码：1428-1444
• 全文大小：902K
• 年卷期：v.6,no.4(April 13, 2010)
• ISSN：1549-9626

文摘

An ab initio computational method, based on the fragment molecular orbital (FMO) method, for calculating nuclear magnetic resonance (NMR) chemical shifts has been developed by introducing the concept of a merged fragment with a cutoff distance. Using point charges or density based on electrostatic potential obtained from FMO calculations, the NMR calculations (GIAO and CSGT) with the 6-31G(d) and 6-311G(d,p) basis sets were performed on α-helix and β-sheet polypeptides. The cutoff distance defines the optimal merged fragment size for NMR calculations. This method accurately reproduces electrostatic effects and magnetic susceptibilities. The chemical shifts determined with a cutoff distance not shorter than 8 Å for both α-helix and β-sheet polypeptides agree well with those calculated by conventional ab initio NMR calculations.