Ab initio modeling of glycosyl torsions and anomeric effects in a model carbohydrate

2-Ethoxy tetrahydropyran

H. Lee Woodcock*, Damian Moran, Richard W. Pastor, Alexander D. MacKerell, Bernard R. Brooks

*Corresponding author for this work

Research output: Contribution to journalArticle

28 Citations (Scopus)

Abstract

A range of ab initio calculations were carried out on the axial and equatorial anomers of the model carbohydrate 2-ethoxy tetrahydropyran to evaluate the level of theory required to accurately evaluate the glycosyl dihedral angle and the anomeric ratio. Vacuum CCSD(T)/CBS extrapolations at the global minimum yield ΔE = Eequatorial - Eaxial = 1.42 kcal/mol. When corrected for solvent (by the IEFPCM model), zero-point vibrations and entropy, ΔG298 = 0.49 kcal/mol, in excellent agreement with the experimental value of 0.47 ± 0.3 kcal/mol. A new additivity scheme, the layered composite method (LCM), yields ΔE to within 0.1 kcal/mol of the CCSD(T)/CBS result at a fraction of the computer requirements. Anomeric ratios and one-dimensional torsional surfaces generated by LCM and the even more efficient MP2/cc-pVTZ level of theory are in excellent agreement, indicating that the latter is suitable for force-field parameterization of carbohydrates. Hartree-Fock and density functional theory differ from CCSD(T)/CBS for ΔE by ∼1 kcal/mol; they show similar deviations in torsional surfaces evaluated from LCM. A comparison of vacuum and solvent-corrected one- and two-dimensional torsional surfaces indicates the equatorial form of 2-ethoxy tetrahydropyran is more sensitive to solvent than the axial.

Original languageEnglish
Pages (from-to)1-10
Number of pages10
JournalBiophysical Journal
Volume93
Issue number1
DOIs
Publication statusPublished - Jul 2007

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