Amino Acids Peptides and Proteins Titration of Amino

Amino Acids, Peptides and Proteins

Titration of Amino Acids • Titration of glycine with Na. OH

Isoelectric Point (p. I) • Isoelectric point, p. I: p. I the p. H at which the majority of amino acid molecules in solution have no net charge ▫ the p. I for glycine, for example, falls between the p. Ka values for the carboxyl and amino groups ▫ the following tables give isoelectric points for the 20 protein-derived amino acids

Isoelectric Point (p. I)

Isoelectric Point (p. I)

Electrophoresis • Electrophoresis: Electrophoresis the process of separating compounds on the basis of their electric charge ▫ electrophoresis of amino acids can be carried out using paper, starch, agar, certain plastics, and cellulose acetate as solid supports • In paper electrophoresis ▫ a paper strip saturated with an aqueous buffer of predetermined p. H serves as a bridge between two electrode vessels

Electrophoresis • Electrophoresis of a mixture of amino acids

Electrophoresis ▫ a sample of amino acids is applied as a spot on the paper strip ▫ an electric potential is applied to the electrode vessels and amino acids migrate toward the electrode with charge opposite their own ▫ molecules with a high charge density move faster than those with low charge density ▫ molecules at their isoelectric point remain at the origin ▫ after separation is complete, the strip is dried and developed to make the separated amino acids visible

Electrophoresis • a reagent commonly used to detect amino acid is ninhydrin