title: Other species in the aqueous environment of a peptide can invert its intrinsic solvated polyproline II/beta propensity: Implications for amyloid formation.
abstract: As we have previously shown, the predominance of the polyproline II conformation in the circular dichroism spectra of aqueous polypeptides is related to its lower energy than that of the beta conformation. To test whether this is still the case in the presence of additional components in the medium, we have calculated the energy difference between these two conformations in an alanine-dipeptide/12-water system without and with the addition of an HCl molecule. We find in the latter case that the beta conformer is of lower energy than the polyproline II. Energy profiles near the minima in both cases also permit conclusions about the relative entropies of these structures. These results emphasize the importance of considering the peptide-plus-medium state as the relevant entity in determining the structural properties of such systems. Such an inversion could be relevant to the formation of amyloid and could thus lead to new strategies for studying its role in the development of neurodegenerative diseases. © 2016 Wiley Periodicals, Inc. Biopolymers 105: 305-311, 2016.
authors.affiliation: LSA Program in Biophysics, University of Michigan, 930 N. University Ave, Ann Arbor, MI, 48109.
authors.forename: Noemi G
authors.initials: NG
authors.lastname: Mirkin
authors.affiliation: LSA Program in Biophysics, University of Michigan, 930 N. University Ave, Ann Arbor, MI, 48109.
authors.forename: Samuel
authors.initials: S
authors.lastname: Krimm
keywords: ab initio; alanine dipeptide; amyloid formation; beta chain; enthalpy; polyproline II; solvation species