title: Solvent-exposed tryptophans probe the dynamics at protein surfaces.
abstract: The dynamics of single tryptophan (W) side chain of protease subtilisin Carlsberg (SC) and myelin basic protein (MBP) were used for probing the surface of these proteins. The W side chains are exposed to the solvent, as shown by the extent of quenching of their fluorescence by KI. Time-resolved fluorescence anisotropy measurements showed that the rotational motion of W is completely unhindered in the case of SC and partially hindered in the case of MBP. The rotational correlation time (phi) associated with the fast local motion of W did not scale linearly with the bulk solvent viscosity (eta) in glycerol-water mixtures. In contrast, phi values of either W side chains in the denatured proteins or the free W scaled almost linearly with eta, as expected by the Stokes-Einstein relationship. These results were interpreted as indicating specific partitioning of water at the surface of the proteins in glycerol-water mixtures.
authors.affiliation: Department of Chemical Sciences, Tata Institute of Fundamental Research, Mumbai 400 005, India.
authors.forename: G S
authors.initials: GS
authors.lastname: Lakshmikanth
authors.forename: G
authors.initials: G
authors.lastname: Krishnamoorthy
mesh_terms: D055592:Biophysical Phenomena; D001703:Biophysics; D005454:Fluorescence Polarization; D005990:Glycerol; D008958:Models, Molecular; D004676:Myelin Basic Protein / Q000737:chemistry; D011487:Protein Conformation; D011489:Protein Denaturation; D011506:Proteins / Q000737:chemistry*; D012997:Solvents; D013381:Subtilisins / Q000737:chemistry; D013499:Surface Properties; D013816:Thermodynamics; D014364:Tryptophan / Q000737:chemistry*; D014783:Viscosity; D014867:Water
chemical_list: D004676:Myelin Basic Protein; D011506:Proteins; D012997:Solvents; D014867:Water; D014364:Tryptophan; D013381:Subtilisins; D005990:Glycerol