Bovine Serum Albumin

Bovine serum albumin (BSA) is a 66.4 kDa, water-soluble protein composed of 583 amino acids. It has a single polypeptide chain with three homologous domains formed by six α-helices. Depending on pH, it undergoes reversible conformational isomerization. The native structure of the protein becomes reactive and flexible on heating. BSA has been used as a model protein in various applications, including immunodiagnostic procedures, cell culture media and clinical chemistry. Serum albumins facilitates drug disposition and efficacy by maintaining osmotic blood pressure.

Bovine Serum Albumin (BSA) has been used:

• to study its adsorption on a planar poly(acrylic acid) (PAA) brush layer through fixed-angle optical reflectometry
• to measure its adsorption on a variety of thin films by means of total internal reflection spectroscopy
• as a constituent of Krebs-Ringer bicarbonate buffer, which acts as a perfusate during placental perfusion

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

Prepared using heat shock fractionation

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.

Remainder mostly globulins.