title: Solvent structure at a hydrophobic protein surface.
abstract: The impact of an extensive, uniform and hydrophobic protein surface on the behavior of the surrounding solvent is investigated. In particular, focus is placed on the possible enhancement of the structure of water at the interface, one model for the hydrophobic effect. Solvent residence times and radial distribution functions are analyzed around three types of atomic sites (methyl, polar, and positively charged sites) in 1 ns molecular dynamics simulations of the alpha-helical polypeptide SP-C in water, in methanol and in chloroform. For comparison, water residence times at positively and negatively charged sites are obtained from a simulation of a highly charged alpha-helical polypeptide from the protein titin in water. In the simulations the structure of water is not enhanced at the hydrophobic protein surface, but instead is disrupted and devoid of positional correlation beyond the first solvation sphere. Comparing solvents of different polarity, no clear trend toward the most polar solvent being more ordered is found. In addition, comparison of the water residence times at nonpolar, polar, positively charged, or negatively charged sites on the surface of SP-C or titin does not reveal pronounced or definite differences. It is shown, however, that the local environment may considerably affect solvent residence times. The implications of this work for the interpretation of the hydrophobic effect are discussed.
authors.affiliation: Laboratory of Physical Chemistry, Swiss Federal Institute of Technology Zürich, Switzerland.
authors.forename: H
authors.initials: H
authors.lastname: Kovacs
authors.forename: A E
authors.initials: AE
authors.lastname: Mark
authors.forename: W F
authors.initials: WF
authors.lastname: van Gunsteren
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D002725:Chloroform / Q000737:chemistry; D003198:Computer Simulation; D064211:Connectin; D018698:Glutamic Acid / Q000737:chemistry; D008239:Lysine / Q000737:chemistry; D000432:Methanol / Q000737:chemistry; D008956:Models, Chemical; D008969:Molecular Sequence Data; D009124:Muscle Proteins / Q000737:chemistry* / Q000378:metabolism; D010446:Peptide Fragments / Q000737:chemistry; D011494:Protein Kinases / Q000737:chemistry* / Q000378:metabolism; D011510:Proteolipids / Q000737:chemistry* / Q000378:metabolism; D011663:Pulmonary Surfactants / Q000737:chemistry* / Q000378:metabolism; D012997:Solvents / Q000737:chemistry*; D013499:Surface Properties; D014867:Water / Q000737:chemistry
chemical_list: D064211:Connectin; D009124:Muscle Proteins; D010446:Peptide Fragments; D011510:Proteolipids; D011663:Pulmonary Surfactants; D012997:Solvents; D014867:Water; D018698:Glutamic Acid; D002725:Chloroform; D011494:Protein Kinases; D008239:Lysine; D000432:Methanol