Bovine serum albumin (BSA) is a water-soluble serum protein, 583 amino acids in length, with a calculated molecular weight of 66,430 Daltons. Six a-helices form its three homologous domains. Depending on pH, bovine serum albumin undergoes reversible conformational isomerization. BSA native structure becomes reactive and flexible on heating.

BSA is a carrier protein for many biomolecules, such as fatty acids, amino acids, and steroids. For its carrier properties, BSA is also widely used in cell culture. BSA also serves antioxidant functions when used in cell culture.

Bovine Serum Albumin has been used in the solution prepared for digestion of tissues. It has been used as a blocking agent in cell spreading assay.

Because BSA is a well-known carrier of fatty acids (FA), control over the particular fatty acids used to culture cell lines is important, for cell culture lines which are sensitive to particular fatty acids. Fatty acid-free BSA is a highly useful reagent for such cell culture experiments, to allow researchers to use such BSA as a carrier for their specific fatty acids specific to their cell culture system. This mitigates potential risks to the cells from FA′s that might be present in non-FA-free BSA.

This BSA product is specifically tested for the following properties:

• Fatty acid free / very low FA content
• Low endotoxin level
• Suitability to use in cell culture

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.