Bovine serum albumin - wikipedia Bovine serum albumin This article is about albumin specific to cows. For the human variant, see human serum albumin. For the family of mammalian albumins, see serum albumin. albumin Identifiers Organism Bos taurus ( domestic cow ) Symbol ALB Entrez 280717 HomoloGene 105925 RefSeq ( mRNA ) NM_180992 RefSeq ( Prot ) NP_851335 UniProt P02769 Other data Chromosome 6 : 91.54 - 91.57 Mb Bovine serum albumin ( also known as BSA or `` Fraction V '' ) is a serum albumin protein derived from cows. It is often used as a protein concentration standard in lab experiments. 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. Lyophilized Bovine Serum Albumin Contents 1 Properties 2 Applications 3 See also 4 References 5 Further reading 6 External links Properties The full - length BSA precursor protein is 607 amino acids ( AAs ) in length. An N - terminal 18 - residue signal peptide is cut off from the precursor protein upon secretion, hence the initial protein product contains 589 amino acid residues. An additional four amino acids are cleaved to yield the mature BSA protein that contains 583 amino acids. Peptide Position Length ( AAs ) MW Da Full length precursor 1 -- 607 607 69,324 Signal peptide 1 -- 18 18 2,107 Propeptide 19 -- 22 478 Mature protein 25 -- 607 583 66,463 Physical properties of BSA : Number of amino acid residues : 583 Molecular weight : 66,463 Da ( = 66.5 kDa ) isoelectric point in water at 25 ° C : 4.7 Extinction coefficient of 43,824 M cm at 279 nm Dimensions : 140 × 40 × 40 Å ( prolate ellipsoid where a = b < c ) pH of 1 % Solution : 5.2 - 7 Optical Rotation : ( α ) : - 61 ° ; ( α ) : - 63 ° Stokes Radius ( r ) : 3.48 nm Sedimentation constant, S × 10 : 4.5 ( monomer ), 6.7 ( dimer ) Diffusion constant, D × 10 cm / s : 5.9 Partial specific volume, V : 0.733 Intrinsic viscosity, η : 0.0413 Frictional ratio, f / f0 : 1.30 Refractive index increment ( 578 nm ) × 10 : 1.90 Optical absorbance, A : 0.667 Mean residue rotation, ( m ' ) : 8443 Mean residue ellipticity : 21.1 ( θ ) ; 20.1 ( θ ) Estimated a-helix, % : 54 Estimated b - form, % : 18 Applications BSA has numerous biochemical applications including ELISAs ( Enzyme - Linked Immunosorbent Assay ), immunoblots, and immunohistochemistry. Because BSA is a small, stable, moderately non-reactive protein, it is often used as a blocker in immunohistochemistry. During immunohistochemistry, which is the process that uses antibodies to identify antigens in cells, tissue sections are often incubated with BSA blockers to bind nonspecific binding sites. This binding of BSA to nonspecific binding sites increases the chance that the antibodies will bind only to the antigens of interest. The BSA blocker improves sensitivity by decreasing background noise as the sites are covered with the moderately non-reactive protein. During this process, minimization of nonspecific binding of antibodies is essential in order to acquire the highest signal to noise ratio. BSA is also used as a nutrient in cell and microbial culture. In restriction digests, BSA is used to stabilize some enzymes during the digestion of DNA and to prevent adhesion of the enzyme to reaction tubes, pipet tips, 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 ( see Bradford protein assay ). BSA is used because of its ability to increase signal in assays, 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. See also Acceptable daily intake Protein allergy Human serum albumin Serum albumin References Jump up ^ Ge S, Kojio K, Takahara A, Kajiyama T ( 1998 ). `` Bovine serum albumin adsorption onto immobilized organotrichlorosilane surface : influence of the phase separation on protein adsorption patterns ''. Journal of Biomaterials Science. Polymer Edition. 9 ( 2 ) : 131 -- 50. PMID 9493841. doi : 10.1163 / 156856298x00479. Jump up ^ Peters T ( 1975 ). Putman FW, ed. The Plasma Proteins. Academic Press. pp. 133 -- 181. Jump up ^ Wright AK, Thompson MR ( Feb 1975 ). `` Hydrodynamic structure of bovine serum albumin determined by transient electric birefringence ''. Biophysical Journal. 15 ( 2 Pt 1 ) : 137 -- 41. PMC 1334600. PMID 1167468. doi : 10.1016 / S0006 - 3495 ( 75 ) 85797 - 3. ^ Jump up to : Putnam FW ( 1975 ). The Plasma Proteins : Structure, Function and Genetic Control. 1 ( 2nd ed. ). New York : Academic Press. pp. 141, 147. ASIN B007ESU1JQ. ^ Jump up to : `` Albumin from bovine serum '' ( PDF ). Sigma - Aldrich. Retrieved 5 July 2013. Jump up ^ Axelsson I ( May 1978 ). `` Characterization of proteins and other macromolecules by agarose gel chromatography ''. Journal of Chromatography A. 152 ( 1 ) : 21 -- 32. doi : 10.1016 / S0021 - 9673 ( 00 ) 85330 - 3. Jump up ^ `` Serum Albumins and Allergies ''. Structural Biology Knowledgebase. National Institute of General Medical Sciences of the National Institutes of Health. October 2013. Jump up ^ `` What Is Immunohistochemistry ( IHC ) ''. Immunohistochemistry. Sino Biological Inc. Jump up ^ Farwell, Alan P. ; Dubord - Tomasetti, Susan A. ( 1999 ). `` Thyroid Hormone Regulates the Expression of Laminin in the Developing Rat Cerebellum ''. Endocrinology : 4221 -- 4227. Jump up ^ >. `` Tips for Reducing ELISA Background ''. Biocompare. Compare Networks. October 8, 2012. ^ Jump up to : Ouellet, Michel ( December 24, 2006 ). `` How Blocking Works in Immunocytochemical Analysis with Serum or BSA ''. MadSci Network : Biochemistry. MadSci Network. Jump up ^ `` Blocker TM BSA ( 10X ) in PBS ''. Thermo Fisher Scientific. Thermo Fisher Scientific Inc. Archived from the original on 2017 - 03 - 30. Jump up ^ `` BSA FAQ ''. Invitrogen. Retrieved 19 January 2012. Further reading Hirayama K, Akashi S, Furuya M, Fukuhara K ( Dec 1990 ). `` Rapid confirmation and revision of the primary structure of bovine serum albumin by ESIMS and Frit - FAB LC / MS ''. Biochemical and Biophysical Research Communications. 173 ( 2 ) : 639 -- 46. PMID 2260975. doi : 10.1016 / S0006 - 291X ( 05 ) 80083 - X. Zhang M, Desai T, Ferrari M ( May 1998 ). `` Proteins and cells on PEG immobilized silicon surfaces '' ( PDF ). Biomaterials. 19 ( 10 ) : 953 -- 60. PMID 9690837. doi : 10.1016 / S0142 - 9612 ( 98 ) 00026 - X. Wise SA, Watters RL ( 2010 - 06 - 30 ). `` Bovine Serum Albumin ( 7 % Solution ) '' ( pdf ). Certificate of Analysis. United States National Institute of Standards & Technology. Retrieved 2011 - 12 - 22. External links Serum Albumin, Bovine at the US National Library of Medicine Medical Subject Headings ( MeSH ) Retrieved from `` https://en.wikipedia.org/w/index.php?title=Bovine_serum_albumin&oldid=797626557 '' Categories : Proteins Hidden categories : All articles with unsourced statements Articles with unsourced statements from May 2014 All articles with dead external links Articles with dead external links from July 2017 Articles with permanently dead external links Talk Contents About Wikipedia Català Čeština Español Français Galego Nederlands Polski Русский Svenska 中文 Edit links This page was last edited on 28 August 2017, at 09 : 18. About Wikipedia

Question: why we use bsa as standard for protein estimation
Answer: ability to increase signal in assays