Thermochemistry of the Dissolution of Dipeptides Containing DL-α-Alanine in Aqueous Solutions of Sodium Dodecyl Sulfate at 298.15 K

Enthalpies of the dissolution of DL-alpha-alanylglycine (AlaGly), DL-alpha-alanyl-DL-alpha-alanine (AlaAla), DL-alpha-alanyl-DL-alpha-valine (AlaVal), and DL-alpha-alanyl-DL-norleucine (AlaNln) in an aqueous solution of sodium dodecyl sulfate (SDS) at SDS concentration of m = 0-0.07 mol kg(-1) and temperature T = 298.15 K are measured via calorimetry. The standard values of the enthalpy of dissolution (Delta H-sol(m)) and the transfer of dipeptides (Delta H-tr(m) ) from water to aqueous SDS solutions are calculated using the experimental data. The dependences of Delta H-sol(m) and Delta H-tr(m) the SDS concentration at a constant concentration of dipeptide are established. Thermochemical characteristics of the transfer of AlaGly, AlaAla, AlaVal, and AlaNln in the investigated range of SDS concentrations are compared. The results are interpreted by considering ion-ion, ion-polar, and hydrophobic-hydrophobic interactions between SDS and dipeptide molecules.