Apparent Molar Volumes of Proline-Leucine Dipeptide in NaCl Aqueous Solutions at 318.15 K

Solubility of proline–leucine dipeptide in water and in aqueous sodium chloride solutions from T=(288.15 to 313.15)K

“…The explanation of this fact is believed to be the release of water molecules to the bulk as a result of the electrostatic interactions between the ions of the electrolyte and the charged groups of the zwitterionic form of these dipeptides. This explanation complies with the observed increase of the limiting partial molar volumes of P-L, when it is transferred from pure water to NaCl aq solutions [9]. The decreasing of the salting-in effect as TABLE 2 Fitted and standard deviation values for the a ij coefficients of equation (1) in (kg 1 + i + j AE m À3 AE mol À(i + j) ) and standard deviation of the fit in (kg AE m À3 ) the temperature decreases may be ascribed to the increasing competition of the hydrophobic solvation, as the temperature decreases, resulting in a salting-out contribution.…”

“…As already pointed out in 3.1 these results signify that the addition of NaCl and the increase of temperature render easier the solubility of P-L in water. The existence of minimum values in all the curves suggests some tendency to the P-L association, being in accordance with the observed negative slope of the linear dependence of limiting partial molar volume as a function of P-L molality in NaCl aq solvents [9].…”

“…In the present case as the solubility of proline-leucine in water increases as the temperature increases we drew the calibration curve at T = 318.15 K (five degrees above the higher temperature studied) to ensure that solubility at T = (288.15, 298.15, 308.15 and 313.15) K could be calculated by interpolation instead of close extrapolation, as before. Density data (79 points) necessary to built the calibration curve has been obtained before [9,23]. Parameters for the double polynomial equation of the form of equation (1) are reported in table 2.…”

“…It has been shown that the addition of co-solutes such as electrolytes, surfactants or other biomolecules to aminoacids and small peptides in aqueous solution, have a strong effect on the hydration of these solutes, generating important changes in their ability to bind other molecules [5][6][7][8][9]. Salting-in and salting-out phenomena, related to the observed changes in the solubility of a nonelectrolyte, produced by the addition of electrolytes to aqueous solutions, have been studied and tentatively correlated with the interactions present in solution before and after the addition of the electrolyte [10][11][12][13][14][15][16].…”

Volumetric and conductometric studies on the interactions of dipeptides with sodium acetate and sodium butyrate in aqueous solutions at T=298.15K

“…The systematic study of peptides can provide valuable information about their behavior in solutions and insight into the conformational stability of proteins. In some previous thermodynamic studies it has been shown that the addition of cosolutes such as electrolytes, surfactants, or other biomolecules to aqueous small peptide solutions would have a strong effect on the hydration of these solutes [2][3][4][5][6][7][8][9][10][11][12][13][14][15], and consequently invoking important changes in their ability to bind other molecules. The obtained thermodynamic data are needed in many applied fields, such as physiology, computer aided design, and optimization of the chemical industrial processes.…”