Insulin is a peptide hormone produced by the pancreatic islets consisting of an A-chain (21 residues) and a B-chain (30 residues) which are linked by two disulfide bonds. It is present at very low concentrations in the bloodstream and regulates the metabolism of carbohydrates, fats and protein. In the presence of zinc atoms, human insulin self-associates to hexamers which is physiologically useful, as the relatively small size of the hexamer allows for dense packing within the secretory granulae of the pancreatic beta-cells. However, since the hexamers are too large for diffusion across the cell membrane, dissociation of the hexamers is a prerequisite for absorption into the circulation. Insulin has no tryptophans, but four tyrosines.

thermal unfolding | tyrosine fluorescence | T_m | T_agg | PR-P-015