molecules Direct interactions with polar groups or peptide backbone Guanidinium Direct Specific binding to acidic Experimental (Tanaka et al. residues and nonspecific (Crystal structure) 2004) binding Guanidinium Direct Preferential interaction with Experimental (Lee & peptide bonds and aromatic (Density Timasheff side chains measurements) 1974) Urea Direct Direct electrostatic Simulation (Mountain & interaction with charged Thirumalai groups on protein 2003) Urea Direct Direct van der Waals Simulation (Canchi et al. interactions and not polar 2010) interactions with protein Urea Direct & Direct interaction with polar Simulation (Bennion & Indirect residues and peptide Daggett 2003) backbone; Weakening of water structure so diminishes hydrophobic effect Urea & Direct Direct solvation of peptide Experimental (Nozaki & Guanidinium backbone (Thermodynamic) Tanford 1970; Bolen & Yang
molecules Direct interactions with polar groups or peptide backbone Guanidinium Direct Specific binding to acidic residues and nonspecific binding Experimental (Crystal structure) (Tanaka et al. 2004) Guanidinium Direct Preferential interaction with peptide bonds and aromatic side chains Experimental (Density measurements) (Lee & Timasheff 1974) Urea Direct Direct electrostatic interaction with charged groups on protein Simulation (Mountain & Thirumalai 2003) Urea Direct Direct van der Waals interactions and not polar interactions with protein Simulation (Canchi et al. 2010) Urea Direct & Indirect Direct interaction with polar residues and peptide backbone; Weakening of water structure so diminishes hydrophobic effect Simulation (Bennion & Daggett 2003) Urea & Guanidinium Direct Direct solvation of peptide backbone Experimental (Thermodynamic) (Nozaki & Tanford 1970; Bolen & Yang