title: Quantitative modelfree analysis of urea binding to unfolded ubiquitin using a combination of small angle X-ray and neutron scattering.
abstract: Characterization of the conformational properties of denatured proteins is essential to our understanding of the molecular basis of protein folding and stability. Here we combine small angle neutron and X-ray scattering to study the interaction of urea with the protein ubiquitin. Comparing coherent intensities scattered at zero angle, and exploiting the scattering densities of H(2)O, D(2)O, ubiquitin, and urea for X-rays and neutrons, we quantitatively determine the number of urea molecules preferentially bound during unfolding of ubiquitin. We find that a pH change from 6.5 to 2.5 triggers recruitment of approximately 20 urea molecules from bulk solution per ubiquitin molecule during the unfolding process.
authors.affiliation: Molecular Biophysics Laboratory, Institut de Biologie Structurale Jean-Pierre Ebel, CEA, CNRS, UJF UMR 5075, 41 Rue Jules Horowitz, 38027 Grenoble, France. frank.gabel@ibs.fr
authors.forename: Frank
authors.initials: F
authors.lastname: Gabel
authors.forename: Malene Ringkjøbing
authors.initials: MR
authors.lastname: Jensen
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Zaccaï
authors.forename: Martin
authors.initials: M
authors.lastname: Blackledge
mesh_terms: D006863:Hydrogen-Ion Concentration; D008958:Models, Molecular; D011485:Protein Binding; D011487:Protein Conformation; D011489:Protein Denaturation; D017510:Protein Folding; D053838:Scattering, Small Angle; D025801:Ubiquitin / Q000737:chemistry / Q000378:metabolism*; D014508:Urea / Q000737:chemistry / Q000378:metabolism*; D014961:X-Ray Diffraction
chemical_list: D025801:Ubiquitin; D014508:Urea