Bovine Serum Albumin

Bovine serum albumin is a protein which has a key role in regulating blood colloidal osmotic pressure. A water-soluble protein composed of 583 amino acids, BSA has a calculated molecular weight of 66,430 Daltons. Six α-helices form three homologous domains of BSA. Depending on pH, BSA undergoes reversible conformational isomerization. The native structure of the protein becomes reactive and flexible on heating.

This BSA product is specifically evaluated and tested for the following properties:

• Very low protease content / protease-free
• Very low fatty acid content / fatty acid-free

Protease-free BSA is especially useful for applications like:

• Enzyme assays
• Protein-based assays
• Protease-sensitive techniques that include:

a. Enzyme immunoassay (EIA)
b. Nucleic acid hybridization
c. Radioimmunoassay (RIA)

Bovine Serum Albumin has been used:

• as a constituent of medium used for the differentiation of human pluripotent stem cells
• in enzyme-linked immunosorbent assay (ELISA) and sandwich ELISA
• to permeabilize fetal cortical cells

This A7030 BSA has specifically been used as a component of blocking buffer in a peptide-based ELISA assay for analysis of COVID-19 / SARS-CoV-2 samples (Poh, C.K. et al., Nat. Commun., 11(1), 2806 (2020)).

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.