: Albumins are a group of acidic proteins which occur in the body fluids and tissues of mammals and in some plant seeds. Serum and plasma albumin is carbohydrate-free and comprises 55-62% of the protein present. However, only about 40% of the total albumin in the body is in the circulating plasma at one time with the remainder being in extracellular spaces with which there is, in general, equilibration about every 24 hours. Bovine albumin is a single polypeptide chain consisting of approximately 583 to 595 amino acid residues and no carbohydrates. At pH 5-7, it contains 17 intrachain disulfide bridges and 1 sulfhydryl group. E.J. Cohn and associates developed one of the first commercial precipitation procedures using an alcohol precipitation. Additional removal of impurities can be accomplished by crystallization, preparative electrophoresis, ion exchange chromatography, affinity chromatography (e.g., ConA-agarose removes glycoproteins), heat treatment (removes globulins), low pH treatment, charcoal treatment, organic solvent precipitation (i.e. isooctane) and low temperature treatment. Charcoal treatment and organic solvent precipitation remove fatty acids. Albumin binds water, Ca2+, Na+ and K+. Due to a hydrophobic cleft, albumin binds fatty acids, bilirubin, hormones and drugs. The main biological function of albumin is to regulate the colloidal osmotic pressure of blood and to a lesser degree to provide cellular nutrition. Human and bovine albumins contain 16% nitrogen.