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Toward Direct Determination of Conformations of Protein Building Units from Multidimensional NMR Experiments Part II: A Theoretical Case Study of Formyl‐ L ‐Valine Amide
Author(s) -
Perczel András,
Császár Attila G.
Publication year - 2001
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/1521-3765(20010302)7:5<1069::aid-chem1069>3.0.co;2-u
Subject(s) - chemical shift , chemistry , conformational isomerism , amide , ab initio , heteronuclear single quantum coherence spectroscopy , anisotropy , computational chemistry , crystallography , nuclear magnetic resonance spectroscopy , nuclear magnetic resonance , molecule , stereochemistry , physics , organic chemistry , quantum mechanics
Chemical shielding anisotropy tensors have been determined for all twenty‐seven characteristic conformers of For‐ L ‐Val‐NH 2 using the GIAO‐RHF formalism with the 6‐31+G* and TZ2P basis sets. The individual chemical shifts and their conformational averages have been compared to their experimental counterparts taken from the BioMagnetic Resonance Bank (BMRB). At the highest level of theory applied, for all nuclei but the amide proton, deviations between statistically averaged theoretical and experimental chemical shifts are as low as 1–3 %. Correlated chemical shift plots of selected nuclei, as function of the respective ϕ , ψ , χ 1 , and χ 2 torsional angles, have been generated. On two‐dimensional chemical shift–chemical shift plots, for example, 1 H NH – 15 N NH and 15 N NH – 13 C α , regions corresponding to major conformational clusters have been identified, providing a basis for the quantitative identification of conformers from NMR shift data. Experimental NMR resonances of nuclei of valine residues have been deduced from 18 selected proteins, resulting in 93 1 H α – 13 C α chemical shift pairs. These experimental results have been compared to relevant ab initio values revealing remarkable correlation between the two sets of data. Correlations of 1 H α and 13 C α values with backbone conformational parameters ( ϕ and ψ ) have also been found for all pairs (e.g. 1 H α / ϕ and 13 C α / ϕ ) but 1 H α / ψ . Overall, the appealing idea of establishing backbone folding of proteins by employing chemical shift information alone, obtained from selected multiple‐pulse NMR experiments (e.g. 2D‐HSQC, 2D‐HMQC, and 3D‐HNCA), has received further support.