Bovine serum albumin, bovine albumin, BSA, also known as "Fraction V", is a serum albumin protein that has numerous biochemical applications including ELISAs (Enzyme-Linked Immunosorbent Assay), immunoblots, and immunohistochemistry. It is also used as a nutrient in cell and microbial culture. In restriction digests, BSA is used to stabilize some enzymes during digestion of DNA and to prevent adhesion of the enzyme to reaction tubes and other vessels. This protein does not affect other enzymes that do not need it for stabilization. BSA is also commonly used to determine the quantity of other proteins, by comparing an unknown quantity of protein to known amounts of BSA. BSA is used because of its stability, its lack of effect in many biochemical reactions, and its low cost since large quantities of it can be readily purified from bovine blood, a byproduct of the cattle industry.
The nickname "Fraction V" refers to albumin being the fifth fraction of the original Edwin Cohn purification methodology that made use of differential solubility characteristics of plasma proteins. By manipulating solvent concentrations, pH, salt levels, and temperature, Cohn was able to pull out successive "fractions" of blood plasma. The process was first commercialized with human albumin for medical use and later adopted for production of BSA.
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Physical properties
- Number of residues: 607
- Molecular weight: 69323.4 Da
- pI in water at 25 °C: 4.7
- Optical absorbance of 1 g/l at 279nm: 0.667 mL mg-1 cm-1 at 279nm[1][1]
- Dimensions: 40x40x140 cubic angstroms Zhang et al.
A 18-residue signal peptide is cut off from the precursor protein upon secretion, hence the precursor has 607 amino acid residues and a molecular weight of c. 69.4 kDa.
References
- The sequence of BSA on NCBI.
- Hirayama, K.: Rapid confirmation and revision of the primary structure of bovine serum albumin by ESIMS and Frit-FAB LC/MS; Biochemical and Biophysical Research Communications, Volume 173, Issue 2, 14 December 1990, Pages 639-646
- Zhang M, Desai T, and Ferrari M. Proteins and cells on PEG immobilized silicon surfaces. Biomaterials 19: 953-960, 1998 [2]
See also
External links
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