title: Molecular dynamics simulation of the antimicrobial salivary peptide histatin-5 in water and in trifluoroethanol: a microscopic description of the water destructuring effect.
abstract: The results of 520 ps molecular dynamics simulation of histatin-5, a small peptide present in human saliva and possessing antimicrobial activity, dissolved in water and in 2,2,2-trifluoroethanol, are reported. The simulations indicate that histatin-5 is destabilized in water and begins to unfold after 250 ps, while in organic solvent it maintains a regular secondary structure throughout the trajectory. Analysis of the peptide-solvent hydrogen bonds indicates that 2,2,2-trifluoroethanol is a poorer proton acceptor than water. The fluorine atom of the alcohol is almost never engaged in a hydrogen bond and the organic solvent interacts mainly with the peptide through its hydroxyl group. For some residues analysis of the solvent residence time indicated longer values for 2,2,2-trifluoroethanol than for water. The most striking difference is related to the number of times the solvent enters and leaves the first coordination shell of the peptide. This value was more than one order of magnitude higher for water than for the alcohol, suggesting that this may be the main cause of alpha-helix destabilization perpetrated by water.
authors.affiliation: National Institute for the Physics of Matter (INFM) and Department of Biology, University of Rome 'Tor Vergata', Rome, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Iovino
authors.forename: M
authors.initials: M
authors.lastname: Falconi
authors.forename: A
authors.initials: A
authors.lastname: Marcellini
authors.forename: A
authors.initials: A
authors.lastname: Desideri
mesh_terms: D000595:Amino Acid Sequence; D000935:Antifungal Agents / Q000737:chemistry* / Q000378:metabolism; D002942:Circular Dichroism; D003198:Computer Simulation; D054808:Histatins; D006860:Hydrogen Bonding; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D012471:Salivary Proteins and Peptides / Q000737:chemistry* / Q000378:metabolism; D012997:Solvents / Q000737:chemistry; D014270:Trifluoroethanol / Q000737:chemistry; D014867:Water / Q000737:chemistry
chemical_list: D000935:Antifungal Agents; C068075:HTN3 protein, human; D054808:Histatins; D012471:Salivary Proteins and Peptides; D012997:Solvents; D014867:Water; D014270:Trifluoroethanol