Jmol overlay pdb
See Textiles for a more detailed discussion of the chemistry of cellulose and silk. Silk proteins are made of fibroin, which is a polymer with a repeate unit of. The corresponding polymeric form of glucose is cellulose. Chitin is a polymer of N-acetylglucosamine, which is an amide derivative of glucose. The nacre is composed of a mixture of organic molecules including chitin, lustrin and silk-like proteins called conchiolins. See Gems & Minerals for a more detailed discussion of the chemistry of CaCO 3. While pearls and mother of pearl are hard substances, they will be dissolved by acids – even by weak acids such as acetic acid, CH 3CO 2H, which is the active ingredient in vinegar, because of they are composed of calcium carbonate. Most pearls today are harvested from freshwater mussels. The material is secreted by the animal as nacre, that builds up in thin, overlapping layers that produce the well-known irridescence associated with pearls and mother of pearl. cm -3) however, mild methods of crystallization can lead to kinetic rather than thermodynamic control of the crystal lattice formed.Under normal conditions, calcite is thermodynamically more stable than aragonite, but at high pressures aragonite is the preferred form as it has a higher density (2.75 vs 2.93 gm
While calcite adopts a trigonal crystal lattice, aragonite is orthorhombic. Pearls and Mother of Pearl, the opalescent coating of some shells opf some bivalve mollusks, is primarily aragonite, a form of calcium carbonate, or a mixture of aragonite and calcite.