title: Collapse of a hydrophobic polymer in a mixture of denaturants.
abstract: The solvent quality of an aqueous mixture of two good solvents, urea and guanidinium chloride (GdmCl), for a hydrophobic polymer was investigated using atomistic molecular dynamics simulations. A counterintuitive collapse of the polymer was found, suggesting that mixing the two denaturants reduces the solvent quality. This cononsolvency of the polymer in the urea + GdmCl mixture is found to be caused by the preferential adsorption of urea on the polymer. The polymer collapses as a result of indirect long-range interactions between monomers resulting from the presence of urea clouds surrounding them. Surprisingly, urea behaves as the better solvent in the mixture not because there exists a stronger affinity of the polymer for urea. Instead, attractive interactions between two unlike denaturant molecules combined with the direct dispersion interactions of the polymer with both denaturants determine the solvent quality of the mixture.
authors.affiliation: Computational Biology Center, IBM Thomas J. Watson Research Center, Yorktown Heights, New York 10598, United States. daspa@us.ibm.com
authors.forename: Payel
authors.initials: P
authors.lastname: Das
authors.forename: Zhen
authors.initials: Z
authors.lastname: Xia
authors.forename: Ruhong
authors.initials: R
authors.lastname: Zhou
mesh_terms: D019791:Guanidine / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D011108:Polymers / Q000737:chemistry*; D011489:Protein Denaturation; D014508:Urea / Q000737:chemistry*
chemical_list: D011108:Polymers; D014508:Urea; D019791:Guanidine