Bovine serum albumin (abbreviated BSA , English Bovine Serum Albumin, BSA ) is a plasma protein of cattle with a molecular weight of 69,000 Da , single-chain, consisting of 607 amino acid residues.
Content
Structure and Properties
Bovine serum albumin (BSA) is the most widely studied and most common blood protein (70% of the total protein composition). Its plasma concentration is 35-55 mg / ml.
Bovine serum albumin is a globule in the form of a flattened ellipsoid of revolution with semi-axes 17 by 42 angstroms, consisting of 607 amino acid residues, their list and amount are presented in the table:
| Ala 48 | Cys 35 | Asp 41 | Glu 58 |
| Phe 30 | Gly 17 | His 16 | Ile 15 |
| Lys 60 | Leu 65 | Met 5 | Asn 14 |
| Pro 28 | Gln 21 | Arg 26 | Ser 32 |
| Thr 34 | Val 38 | Trp 2 | Tyr 21 |
BSA has a rather complex spatial structure, forming three domains, each of which, in turn, is divided into two subdomains (AB and C). Each subdomain can be divided into 3 helices X, Y, and Z. The secondary structure of BSA, according to (1H NMR) data, comprises 50-68% alpha helices, 16-18% beta folds. The tertiary structure is formed by disulfide bonds, of which there are 17 pieces in the BSA molecule (by the number of cysteine amino acid residues). The molecular weight of BSA = ~ 69 kDa.
It is a convenient model for studying the properties of globular proteins.
Laboratory Applications
Due to the availability of starting material, stable isolation techniques, and, as a result, relatively low price and good study of properties, bovine serum albumin is widely used in laboratory practice.
BSA is used as a standard in various methods for the quantitative determination of proteins, as a standard for the molecular weight of proteins (marker) in gel chromatography and electrophoresis of proteins in a denatured state ( SDS-PAGE ), and also as a standard antigen in determining changes in the immune response under the influence of immunomodulators or other factors. It is also used to stabilize certain enzymes, in particular restriction endonucleases. Prevents adhesion of enzymes to the walls of the vessel.
Getting
Primitive methods:
- “Water is poured into the blood serum (blood lacking fibrin) in an amount exceeding the volume of serum by a factor of twenty, then the globulin is precipitated by carefully adding acetic acid. Having allowed the liquid to settle, it is filtered and neutralized with soda, evaporated at 40 ° C and most of the salts are isolated by dialysis. ”
- “For technical purposes, it is prepared by releasing blood directly from the animal into shallow zinc cups with a capacity of several liters. They cool her in them until she curls up; Care must be taken not to agitate freshly released blood, therefore, the place where the operation is performed should be chosen near the animal. When the blood finally coagulates, it is transferred to the same cups with perforated bottoms and a blood clot is cut into small pieces to allow the serum to drain. The serum is collected and evaporated at a moderate temperature, the remainder is called albumin. Any shaking should be avoided, as this will cause the red blood cells to burst and the color of the product will deteriorate. Five bulls produce about 20 liters of serum and about 2 kg of albumin. ”