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Explore the titration of amino acids like glycine, learn about isoelectric points, and understand electrophoresis methods for amino acid separation. Discover the role of ninhydrin in amino acid detection through paper electrophoresis.
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Titration of Amino Acids • Titration of glycine with NaOH
Isoelectric Point (pI) • Isoelectric point, pI: the pH at which the majority of amino acid molecules in solution have no net charge • the pI for glycine, for example, falls between the pKa values for the carboxyl and amino groups • the following tables give isoelectric points for the 20 protein-derived amino acids
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 pH 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