Bovine Serum Albumin

Bovine serum albumin is a model protein in various studies and is made up of 583 amino acids. It is a water-soluble protein with a molecular weight of 66.4kDa. Six α-helices form three homologous domains of BSA. Depending on pH, it undergoes reversible conformational isomerization. The native structure of the protein becomes reactive and flexible on heating.

Bovine Serum Albumin has been used in the washing solution for flow cytometry analysis, tissue digestion solution and blocking solution for ELISA (enzyme-linked immunosorbent assay). It has also been used in the resuspension buffer for flow cytometry.

Bovine serum albumin is broadly used as an additive to cell culture media, especially serum-free media. It provides a range of benefits including protection from oxidative damage and stabilization of other media components such as fatty acids and pyridoxal.

Certain conformational and primary-sequence epitopes of BSA are suspected allergens in human beef and milk allergies.

Often referred to as Cohn fraction V; this product is prepared by a modified method of the Cohn cold ethanol fractionation method.

Serum albumin may be referred to as Fraction V. This naming convention is taken from the original Cohn method of fractionating serum proteins using cold ethanol precipitation. Serum albumin was found in the fifth ethanol fraction using Cohn′s method. Since then, the term "Fraction V" has been used by some to describe serum albumin regardless of the method of preparation. Others have used this term to describe serum albumin purified by ethanol fractionation methods that have been highly modified since the original Cohn method was described. Sigma-Aldrich manufactures and distributes serum albumins purified from a variety of primary methods including the true Cohn fractionation method, modified ethanol fractionation methods, heat shock and chromatography. Additional purification steps may include crystallization or charcoal filtration.