Elastin

ELASTIN, a substance from the group of albuminoids, that enters into the composition of connective tissue of higher animals, forming elastic fibers. There is especially much E. in elastic tissue, for example, in ligamentum nuchae; the shells of eggs of some reptiles and fish also apparently consist of E. To obtain E., the elastic tissue is finely ground, well washed with water, and extracted for several days with a half-saturated solution of lime; after washing the lime away with water, it is treated several times with 10% boiling acetic acid and 5% HCl; the acid is washed away with water and the residue is boiled with alcohol and ether, dried at 100° and triturated in a mortar. E., obtained by different methods and from different connective tissue, somewhat differs in composition. It has not yet been established whether E. is chemically a homogeneous body. Pure dry E. is a yellowish-white powder, insoluble in water, alcohol and ether. E. is very stable with respect to chemical reagents. Finely ground E. partially dissolves on long standing at room temperature in 0.2% HCl, completely dissolves when heated in 1% KOH, at room temperature in a concentrated solution of KOH; it is very slowly digested by pepsin and trypsin. Of amino acids, E. contains glycine-25.8%, alanine-6.6%, valine-2.0%, leucine-21.4%, glutamic acid-0.8%, proline-11.5%, phenylalanine-3.9%, tyrosine-0.34%; diamino acids in very small quantities; tryptophan and aspartic acid have not been found, sulfur content is about 0.1-0.4%.