title: Thermodynamics of the Trp-cage miniprotein unfolding in urea.
abstract: The thermodynamic properties of unfolding of the Trp-cage mini protein in the presence of various concentrations of urea have been characterized using temperature-induced unfolding monitored by far-UV circular dichroism spectroscopy. Analysis of the data using a two-state model allowed the calculation of the Gibbs energy of unfolding at 25 degrees C as a function of urea concentration. This in turn was analyzed by the linear extrapolation model that yielded the dependence of Gibbs energy on urea concentration, i.e. the m-value for Trp-cage unfolding. The m-value obtained from the experimental data, as well as the experimental heat capacity change upon unfolding, were correlated with the structural parameters derived from the three dimensional structure of Trp-cage. It is shown that the m-value can be predicted well using a transfer model, while the heat capacity changes are in very good agreement with the empirical models based on model compounds studies. These results provide direct evidence that Trp-cage, despite its small size, is an excellent model for studies of protein unfolding and provide thermodynamic data that can be used to compare with atomistic computer simulations.
authors.affiliation: Center for Biotechnology and Interdisciplinary Studies, Department of Biology, Rensselaer Polytechnic Institute, Troy, New York 12065, USA.
authors.forename: Lucas N R
authors.initials: LN
authors.lastname: Wafer
authors.forename: Werner W
authors.initials: WW
authors.lastname: Streicher
authors.forename: George I
authors.initials: GI
authors.lastname: Makhatadze
mesh_terms: D003198:Computer Simulation; D010455:Peptides / Q000737:chemistry* / Q000378:metabolism*; D011489:Protein Denaturation / Q000187:drug effects; D017510:Protein Folding / Q000187:drug effects; D017433:Protein Structure, Secondary; D013816:Thermodynamics; D014364:Tryptophan / Q000737:chemistry*; D014508:Urea / Q000494:pharmacology*
chemical_list: D010455:Peptides; D014364:Tryptophan; D014508:Urea