Bovine Serum Albumin (BSA)

Albumin is the most abundant protein of the serum (about 60% of the total protein content of plasma). which regulates the osmotic pressure and pH of blood, and transports a wide variety of endogenous and exogenous compounds such as fatty acids, metal, amino acids, steroids and drugs.
Bovine Serum Albumin (BSA) also referred as Fraction V (as it has been originally found in the fifth ethanol fraction using Cohn′s cold ethanol precipitation method) is a Serum Albumin Protein derived from bovine serum with a molecular weight of 66.4kDa. It is a water-soluble protein which consists of 583 amino acids. It consists of three homologous domains which have been formed by six α-helices.
Fraction V is originated from the cold ethanol precipitation method used by Cohn to fractionate serum proteins. Serum albumin was found in the fifth ethanol fraction using Cohn′s method. Later on, some people used this term “Fraction V” to refer to serum albumin regardless of the method of preparation. Others have used this term to describe serum albumin purified by ethanol fractionation methods, it worth noting however, cold ethanol precipitation method has been highly modified since the original Cohn method. Different methods are used to purify serum including Cohn fractionation method, modified ethanol fractionation methods, heat shock and chromatography.

BSA applications

 BSA is widely used in various applications including immunology, biochemistry, and biotechnology and molecular biology. ELISA (Enzyme-Linked Immunosorbent Assay), immunoblots (Western blot and dot blot), and immunocytochemistry (immunohistochemistry and immunofluorescence microscopy) are the most common applications for BSA in immunology. In cell and microbial culture, BSA used as a nutrient. In molecular biology, BSA is used as a stabilizer of some of restriction enzymes during digestion of DNA. It also prevents adhesion of the enzyme to reaction tubes, pipet tips, and other vessels. It is also widely used for quantitation of proteins amount in assays such as the Bradford Protein Assay.
Due to its lack of effect on other proteins, BSA is considered as a universal blocking reagent in many applications. It’s low cost, beside its stability to increase signal in assays and also its lack of interfere with other biochemical and biological reaction make the BSA a popular reagent for many biological studies and applications.