Rhodopsin (also known as visual purple) is a light-sensitive receptor protein involved in visual phototransduction. It is named after ancient Greek ῥόδον (rhódon) for rose, due to its pinkish color, and ὄψις (ópsis) for sight. Rhodopsin is a biological pigment found in the rods of the retina and is a G-protein-coupled receptor (GPCR). It belongs to a group of photoswitchable opsins. Rhodopsin is extremely sensitive to light, and thus enables vision in low-light conditions. When rhodopsin is exposed to light, it immediately photobleaches. In humans, it is regenerated fully in about 30 minutes, after which rods are more sensitive.
Rhodopsin was discovered by Franz Christian Boll in 1876.
Insulin-like growth factor 1 (IGF-1) , also called somatomedin C, is a hormone similar in molecular structure to insulin which plays an important role in childhood growth, and has anabolic effects in adults. IGF-1 is a protein that in humans is encoded by the IGF1 gene. IGF-1 consists of 70 amino acids in a single chain with three intramolecular disulfide bridges. IGF-1 has a molecular weight of 7,649 Daltons. In dogs, an ancient mutation in IGF1 is the primary cause of the toy phenotype. IGF-1 is produced primarily by the liver. Production is stimulated by growth hormone (GH). Most of IGF-1 is bound to one of 6 binding proteins (IGF-BP). IGFBP-1 is regulated by insulin. IGF-1 is produced throughout life; the highest rates of IGF-1 production occur during the pubertal growth spurt. The lowest levels occur in infancy and old age. A synthetic analog of IGF-1, mecasermin, is used in children for the treatment of growth failure.