Interaction of some hydrophobic amino acids, peptides, and protein with aqueous 3-chloro-1,2-propanediol and 3-chloro-1-propanol: Biophysical studies

Abstract

The apparent molar volume V 2, ϕ , apparent molar isentropic compressibility K S ,2, ϕ , and heat of dilution ( q) of aqueous glycine, alanine, α-amino butyric acid, valine, leucine, diglycine, triglycine, and hen egg white lysozyme have been determined in aqueous solutions of 3-chloropropano-1-ol and 3-chloropropan-1,2-diol solutions at T = 298.15 K. These data have been used to calculate the infinite dilution standard partial molar volume V 2 , m 0 , partial molar isentropic compressibility K S , 2 , m 0 , and enthalpy of dilution Δ dil H° of the amino acids and peptides in aqueous 3-chloropropano-1-ol and 3-chloropropan-1,2-diol, and the standard partial molar quantities of transfer of the amino acids and peptides to the aqueous alcohol and diol solutions. The linear correlation of V 2 , m 0 for a homologous series of amino acids has been utilized to calculate the contribution of the charged end groups ( NH 3 + , COO - ) , CH 2 group and other alkyl chains of the amino acids to the values of V 2 , m 0 . The results on the standard partial molar volumes of transfer, compressibility and enthalpy of dilution from water to aqueous alcohol and diol solutions have been correlated and interpreted in terms of ion–polar, ion–hydrophobic, and hydrophobic–hydrophobic group interactions. The heat of dilution of these amino acids, peptides, and hen egg white lysozyme measured in aqueous solutions of 3-chloropropano-1-ol and 3-chloropropan-1,2-diol by using isothermal titration calorimetry along with the volumetric, compressibility, and calorimetric results on amino acid and peptides have been correlated to understand the nature of interactions operating in these systems.