title: Alcohol induced structural and dynamic changes in β-lactoglobulin in aqueous solution: a neutron scattering study.
abstract: Structural and dynamic properties of β-lactoglobulin (β-LG) were revealed as a function of alcohol concentration in ethanol- and trifluoroethanol(TFE)-water mixtures with circular dichroism (CD), small-angle neutron scattering (SANS) and quasi-elastic neutron scattering (QENS). The CD spectra showed that an increase in TFE concentration promotes the formation of the β-sheet structure of β-LG. The SANS-intensities were fitted using form factors for two attached spheres for the native and native-like states of the protein. At higher alcohol concentrations, where aggregation takes place, a form factor modelling diffusion limited colloidal aggregation (DLCA) was employed. The QENS-data were analyzed in terms of internal motions for all alcohol concentrations. While low concentrations of TFE (10% (v/v)) lead to an increase of the mean square amplitudes of vibrations <u(2)> and a retention of a native-like structure - but not to an increase of the characteristic radius of proton diffusion processes a. Addition of 20% (v/v) of TFE induces aggregation, going along with a further increase of <u(2)>. Further increase of TFE concentration to 30% (v/v) changes the nanoscale structure of the oligomeric nucleate, but induces no further significant changes in <u(2)>. The present study underlines the necessity of methods sensitive to the dynamics of a system to obtain a complete picture of a molecular process.
authors.affiliation: Department of Chemistry, Fukuoka University, Fukuoka, Japan. kyoshida@fukuoka
authors.forename: Koji
authors.initials: K
authors.lastname: Yoshida
authors.forename: Karsten
authors.initials: K
authors.lastname: Vogtt
authors.forename: Zunbeltz
authors.initials: Z
authors.lastname: Izaola
authors.forename: Margarita
authors.initials: M
authors.lastname: Russina
authors.forename: Toshio
authors.initials: T
authors.lastname: Yamaguchi
authors.forename: Marie-Claire
authors.initials: MC
authors.lastname: Bellissent-Funel
mesh_terms: D000818:Animals; D002417:Cattle; D002942:Circular Dichroism; D000431:Ethanol / Q000737:chemistry*; D007700:Kinetics; D007782:Lactoglobulins / Q000737:chemistry*; D033363:Neutron Diffraction; D017510:Protein Folding; D020033:Protein Isoforms / Q000737:chemistry; D017433:Protein Structure, Secondary; D053838:Scattering, Small Angle; D012996:Solutions; D014270:Trifluoroethanol / Q000737:chemistry*; D014867:Water; D014961:X-Ray Diffraction
chemical_list: D007782:Lactoglobulins; D020033:Protein Isoforms; D012996:Solutions; D014867:Water; D000431:Ethanol; D014270:Trifluoroethanol