The Volta metric and Thermodynamic Behavior of Cysteine and its Interaction with Albumin

The work involves the quantitative determination of (L cysteine) using (SWV). L cysteine gives a well- defined reduction peak at (-0.546) volts against[(Ag/AgCl,sat. KCl)] using phosphate buffer solution (pH = 7).The relationship between the diffusion current and concentration over the range [2 10-6(M) 3.98 10-7(M)] is linear with a correlation coefficient of (0.9974). At higher concentrations above [ 3 10-6] molar, the reduction peak of the (L cysteine )divided into two peaks where the original one belongs to (L cysteine) at (-0.52 volt) and a small peak at (-0.46 volt) which may be belong to the formation of (L cystine ) amino acid.
The interaction of Albumin-Amino acid (L-cysteine) was also carried out and It was found that the reduction peak of the amino acid decreases with increasing addition amount of Albumin. The binding constant (K) is calculated at different temperatures. Vant Hoff relation was applied to obtain the thermodynamics parameters (H, S,G). The interaction seems to be of the ( ion-ion) type.