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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. == 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 4 amino acids are cleaved to yield the mature BSA protein that contains 583 amino acids. 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−1cm−1 at 279 nm * Dimensions: 140 × 40 × 40 Å (prolate ellipsoid where a = b < c) * pH of 1% Solution: 5.2-7 〔(【引用サイトリンク】url=http://www.sigmaaldrich.com/etc/medialib/docs/Sigma/Product_Information_Sheet/b4287pis.Par.0001.File.tmp/b4287pis.pdf )〕 * Optical Rotation: ()259: -61°; ()264: -63°〔〔 * Stokes Radius (rs): 3.48 nm * Sedimentation constant, S20,W × 1013: 4.5 (monomer), 6.7 (dimer)〔〔 * Diffusion constant, D20,W × 107 cm2/s: 5.9〔〔 * Partial specific volume, V20: 0.733〔〔 * Intrinsic viscosity, η: 0.0413〔〔 * Frictional ratio, f/f0: 1.30〔〔 * Refractive index increment (578 nm) × 10−3: 1.90〔〔 * Optical absorbance, A279 nm1 g/L: 0.667〔〔 * Mean residue rotation, ()233: 8443〔〔 * Mean residue ellipticity: 21.1 ()209 nm; 20.1 ()222 nm〔〔 * Estimated a-helix, %: 54〔〔 * Estimated b-form, %: 18〔〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「bovine serum albumin」の詳細全文を読む スポンサード リンク
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