Collagen
Collagen
Collagen is the most important protein structure in the body, being presented in large quantities in skin (70 of dry weight) , bones, tendons, and cartilage, cornea, glomeruli and blood vessels, … etc. (104) Also more than half of the body collagen is in the skeletonm. (105) Collagen is a protein which is resembled in the endoplasmic reticulum in the usual way after the transcription of DNA into RNA and the translation of the nucleotide sequence into amino acid sequence .(106) .Collagen is the most important structure element in BPS where BPS have no synthetic or renewal mechanism such as provided to the fiber blasts present in native valves to replace the collagen that is gradually broken down. (107) Collagen has also been observed , in the presence of human skin, collagen in cultured lymphocytes, as sclerosis patients produce lymphokines that enhance collagen production by fibroblasts and are chemotactic for skin fibroblasts. (108) Collagen plays an important role in the early stages of healing and the formation of the granulation matrix. Production of collagen remains a major process in wound repair for several weeks after wound closure , the collagen continues to undergo remodeling for 2 years or more until the injured tissue is finally restored. (109) The basic collagen molecules are composed of three polypeptide alpha chains which are found into a characteristic left handed triple helix . (110) The three chains are held together
by Hydrogen bonds and intermolecular parallel-links. This unusual conformation gives the molecular a rigid rod-like Structure. (108) Collagen molecules are present in the ground substance of growing connective tissue and can be extracted in cold neutral salt solution and collagen may present physical and possibly chemical different parts of the body and may not always take the form of fibers. (111)
