Topics - Protein
A protein is a biological polymer comprising a number of different a
-amino acids joined together by peptide bonds. The peptide bond is formed by the condensation of the carboxyl group of one amino acid with the amino group of a second amino acid. The condensation of a few amino acids (10-20) produce small biopolymers which are called peptides
; the condensation of peptides in the same manner yield polypeptides
and the condensation of polypeptides yield proteins
that can have extremely high molecular weights. There are 20 a
-amino acids associated with mammalian proteins. The groups attached to the peptide bond may be dispersive (cf Londonís dispersive forces or hydrophobic), polar (or hydrophilic) or ionic. If dispersive groups dominate in the proteiní then the overall property of the protein will be dispersive in character (hydrophobic) and interact readily with dispersive substances. If polar groups dominate in the protein molecule it will be polar in character (hydrophilic) and interact readily with polar substances. Proteins are separated by liquid chromatography using short chain dispersive bonded phases as the stationary phase. The use of short chains is usually necessary as longer chains can have excessively strong interaction with the dispersive parts of the protein which can cause protein denaturation.