Collagen，a major component of the extracellular matrix，is a fibrous protein that provides tensile strength to tissues giving them structural integrity. Collagen and its derivative，gelatin，have been widely used in medical，pharmaceutical and consumer products for more than 100 years. Collagens are fibrous，extracellular matrix proteins with high tensile strength and are the major components of connective tissue，such as tendons and cartilage. All collagens contain a triple helix domain and frequently show lateral self-association in order to form complex connective tissues. Several collagens also play a role in cell adhesion，important for maintaining normal tissue architecture and function. The extensive family of COL gene products (collagens) is composed of several chain types，including fibril-forming interstitial collagens (types I，II，III and V) and basement membrane collagens (type IV)，each type containing multiple isoforms.
