title: Theoretical study of the competition between intramolecular hydrogen bonds and solvation in the Cys-Asn-Ser tripeptide.
abstract: A study of the competition between intra- and intermolecular hydrogen bonds and its influence on the stability of the Cys-Asn-Ser tripeptide in aqueous solution was performed by using the averaged solvent electrostatic potential from molecular dynamics method (ASEP/MD). The model combines a DFT-B3LYP/6-311+G(d) quantum treatment in the description of the solute molecule with NVT molecular dynamics simulations in the description of the solvent. In gas phase, the most stable structure adopts a C5 conformation. Somewhat higher in energy are found the PP(II) and C7eq structures. In solution, the stability order of the different conformers is reversed: the PP(II) structure becomes the most stable, and the C5 structure is strongly destabilized. The conformational equilibrium is shifted toward conformations in which the intramolecular hydrogen bonds (IHB) have been substituted with intermolecular hydrogen bonds with the water molecules. The solvent stabilizes extended structures without IHBs that are not stable in vacuum. The effect of the protonation state on the conformational equilibrium was also analyzed.
authors.affiliation: Química Física, Universidad de Extremadura, Avenida de Elvas, s/n 06071 Badajoz, Spain.
authors.forename: Catalina
authors.initials: C
authors.lastname: Soriano-Correa
authors.forename: Francisco J
authors.initials: FJ
authors.lastname: Olivares del Valle
authors.forename: Aurora
authors.initials: A
authors.lastname: Muñoz-Losa
authors.forename: Ignacio
authors.initials: I
authors.lastname: Fdez Galván
authors.forename: M Elena
authors.initials: ME
authors.lastname: Martín
authors.forename: Manuel A
authors.initials: MA
authors.lastname: Aguilar
mesh_terms: D004583:Electrons; D005740:Gases / Q000737:chemistry; D006860:Hydrogen Bonding; D056004:Molecular Dynamics Simulation; D009842:Oligopeptides / Q000737:chemistry*; D011487:Protein Conformation; D011789:Quantum Theory; D012997:Solvents / Q000737:chemistry*; D013816:Thermodynamics
chemical_list: C552587:Cys-Asn-Ser tripeptide; D005740:Gases; D009842:Oligopeptides; D012997:Solvents