Interaction of water vapour with twenty different poly-L-amino acids and their excess hydration in presence of sodium chloride.
Using the isopiestic vapour pressure technique, the magnitudes of excess binding of water and NaCl per mole of twenty different poly-L-amino acid residues, respectively in the presence of different bulk molefractions (X2) of NaCl have been evaluated from the mathematical expressions for the Gibbs surface excesses. At certain high ranges of NaCl concentration, the plot of -Gamma1 (2) versus X1/X2 becomes linear, so that moles of water and NaCl, respectively bound per mole of amino acid residue can be evaluated. -Gamma(2)1 is the excess moles of H20 per mole of amino acid residue and X1 and X2 stand for mole fractions of the water and NaCl, respectively in the sample system. Also, using the integrated form of the Gibbs absorption equation, the values of standard free energy change (deltaG(0)) for the excess adsorption of NaCl per kg of poly-L-amino acids have been evaluated. These values are all positive as a result of positive excess hydration of polyamino acids. The standard free energy of excess hydration deltaG(0)hy (equal to -deltaG(0)) is negative due to spontaneous excess hydration of polyamino acid in the presence of a salt.
Department of Food Technology & Biochemical Engineering, Jadavpur University, Kolkata 700 032.
N
N
Ghosh
P
P
Dutta
P
P
Mahapatra
K P
KP
Das
D K
DK
Chattoraj
D000596:Amino Acids / Q000737:chemistry*; D012965:Sodium Chloride / Q000737:chemistry*; D013816:Thermodynamics; D014835:Volatilization; D014867:Water / Q000737:chemistry*
D000596:Amino Acids; D014867:Water; D012965:Sodium Chloride