Case D A
Department of Molecular Biology, Scripps Research Institute, La Jolla, CA 92037, USA.
J Biomol NMR. 1995 Dec;6(4):341-6. doi: 10.1007/BF00197633.
Density functional chemical shielding calculations are reported for methane molecules placed in a variety of positions near aromatic rings of the type found in proteins and nucleic acids. The results are compared to empirical formulas that relate these intermolecular shielding effects to magnetic anisotropy ('ring-current') effects and to electrostatic polarization of the C-H bonds. Good agreement is found between the empirical formulas and the quantum chemistry results, allowing a reassessment of the ring-current intensity factors for aromatic amino acids and nucleic acid bases. Electrostatic interactions contribute significantly to the computed chemical shift dispersion. Prospects for using this information in the analysis of chemical shifts in proteins and nucleic acids are discussed.
本文报道了对处于蛋白质和核酸中常见类型芳香环附近各种位置的甲烷分子进行的密度泛函化学屏蔽计算。将结果与将这些分子间屏蔽效应与磁各向异性（“环电流”）效应以及C - H键的静电极化相关联的经验公式进行了比较。发现经验公式与量子化学结果之间具有良好的一致性，从而能够重新评估芳香族氨基酸和核酸碱基的环电流强度因子。静电相互作用对计算出的化学位移分散有显著贡献。文中还讨论了在蛋白质和核酸化学位移分析中使用该信息的前景。
