title: Comparison of β-sheets of capped polyalanine with those of the tau-amyloid structures VQIVYK and VQIINK. A density functional theory study.
abstract: We present ONIOM calculations using B3LYP/d95(d,p) as the high and AM1 as the low level on parallel β-sheets containing from two to ten strands of Ac-VQIVYK-NHMe and Ac-VQIINK-NHMe, as well as both parallel and antiparallel Ac-AAAAAA-NHMe. We find that the first two sequences form more stable sheets due to the additional H-bonding between the Q's in the side chains of both and the N's in the side chain of Ac-VQIINK-NHMe. However, the H-bonds in the amyloid chains are significantly weakened by attractive strain, which prevents all the interstrand H-bonds from achieving their optimal geometries simultaneously and requires high distortion energies for the individual strands in the sheets. The antiparallel Ac-AAAAAA-NHMe's are generally more stable and more cooperative than the parallel sheets, principally due to the higher distortion energies of the latter.
authors.affiliation: Department of Chemistry, City University of New York-Hunter College and Graduate School, 695 Park Avenue, New York, New York 10065, United States.
authors.forename: Joshua A
authors.initials: JA
authors.lastname: Plumley
authors.forename: J J
authors.initials: JJ
authors.lastname: Dannenberg
mesh_terms: D000682:Amyloid / Q000737:chemistry*; D006860:Hydrogen Bonding; D008432:Mathematical Computing; D009842:Oligopeptides / Q000737:chemistry*; D010455:Peptides / Q000737:chemistry*; D017433:Protein Structure, Secondary; D016875:tau Proteins / Q000737:chemistry*
chemical_list: D000682:Amyloid; D009842:Oligopeptides; D010455:Peptides; D016875:tau Proteins; C019529:polyalanine