Volumetric properties of aqueous solutions of amino acids from the singular to critical temperature |
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Authors: | V. P. Korolev |
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Affiliation: | 1. Institute of Solution Chemistry, Russian Academy of Sciences, Ivanovo, Russia
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Abstract: | The partial volume -V 2 0 of amino acids in aqueous solution is assumed to be zero for T = 227 K (singular temperature) and T= T c (critical temperature). The literature data for -V 2 0(T) of ten amino acids at 278–328 K are reproduced by the two-parameter equation with a standard deviation of 0.06–0.16 cm3/mol. Only for asparagine and tryptophan the standard deviation exceeds 0.3 cm3/mol. In the case of glycine and alanine, the relation -V 2 0(T) in the high temperature range is obtained. -V 2 0 is divided into contributions (?-H 2 0/?p) T and —T·(?-S 2 0/?p) T . Their dependence on the temperature and amino acid nature is discussed. Positive values of ?-C 2 0/?p) T characterize amino acids as water structure breakers; however, the differentiation of compounds by this feature is not successful. The behavior of amino acids in aqueous solutions is compared with the behavior of urea. |
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