Density Functional Theory and Biomolecules: A Study of Glycine, Alanine, and Their Oligopeptides

摘要: We present density functional (DF) calculations, using a pseudopotential scheme and plane waves as basis functions, for isolated molecules of the amino acids glycine alanine, small oligopeptides composed periodic (infinite) polyalanine helices. calculate relative energies geometries low-lying isomers alanine variety oligopeptide various DF formulations electron exchange correlation (LDA, PBE, BLYP, BP). Comparison is made with other theories experiment where possible. The free molecule equilibrium agree well limited experimental data post-Hartree−Fock (post-HF) calculations. inclusion gradient-corrected (nonlocal) functionals essential when hydrogen bonds play role in determining energies. This especially true type N···H−O, which appear two alanine. obtain most reliable results BL...