title: Amino acid behavior in aqueous denaturant solutions: temperature dependence of the L-histidine-amide interaction.
abstract: We have studied the thermodynamics of the pair interaction between aromatic amino acid-l-histidine and nonelectrolyte denaturing globular proteins-hydrophilic urea (U) and presumably hydrophobic dimethylformamide (DMF) in the temperature range of 288-328 K. Our study does indicate for the first time the anomalous temperature dependence of the enthalpies and entropies of the l-histidine-U and l-histidine-DMF interaction in water, which is consistent with the previously reported results for water-urea (U) and water-U-l-phenylalanine systems. This phenomenon is found to be closely related to the behavior of water, since in all cases, the extrema observed arise in the temperature range of 300-308 K, where the temperature dependence of the heat capacity of pure water passes through the minimum. The amino acid-urea interaction is shown to be accompanied in a wide temperature range by a large negative enthalpy change, which reveals a strong tendency of urea binding with polar and charged groups of proteins.
authors.affiliation: Institute of Solution Chemistry of Russian Academy of Sciences, Ivanovo, Russian Federation. kustov@isuct.ru
authors.forename: Andrey V
authors.initials: AV
authors.lastname: Kustov
authors.forename: Nataliya L
authors.initials: NL
authors.lastname: Smirnova
authors.forename: Dmitriy V
authors.initials: DV
authors.lastname: Batov
mesh_terms: D000577:Amides / Q000737:chemistry*; D004126:Dimethylformamide / Q000737:chemistry; D006639:Histidine / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D011489:Protein Denaturation; D012996:Solutions; D013696:Temperature; D014508:Urea / Q000737:chemistry; D014867:Water / Q000737:chemistry*
chemical_list: D000577:Amides; D012996:Solutions; D014867:Water; D006639:Histidine; D004126:Dimethylformamide; D014508:Urea