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The mysterious world of bovine serum albumin: Why is it a "universal assistant" in the laboratory?
Bovine serum albumin (BSA or "Fraction V") is a serum albumin from cattle that is widely used in laboratories, particularly as a standard for protein concentration. The "Fraction V" in the protein's name comes from the fifth fraction extracted using the time-honored Edwin Cohn purification method, which exploits the different solubility properties of plasma proteins. During this process, the scientists gradually extracted different "fractionations" by varying solvent concentration, pH, salt concentration and temperature. This method was first used for the commercialization of human albumin and was subsequently adopted for the production of bovine serum albumin.
"Bovine serum albumin's diversity and stability make it an ideal partner for many scientific experiments."
Properties of bovine serum albumin
The full-length precursor polypeptide of BSA consists of 607 amino acids. After secretion, the 18-residue signal peptide at the N-terminus is cleaved, so the initial product consists of 589 amino acid residues. Then 6 amino acids are removed to form the mature BSA protein, which contains 583 amino acids. BSA has three homologous but structurally different domains, called I, II and III respectively, and each domain is subdivided into two sub-domains, A and B.
The physical properties of BSA are as follows:
- Number of amino acid residues: 583
- Molecular weight: 66,463 Da (approximately 66.5 kDa)
- Isoelectric point at 25°C: 4.7
- Extinction coefficient at 279 nm: 43,824 M⁻¹cm⁻¹
In addition, the BSA measures approximately 140 × 40 × 40 Å and exhibits an oval shape with a long paddle.
Function
Like other serum albumins, BSA plays a key role in maintaining phosphonic acid pressure within capillaries, transporting fatty acids, bilirubin, minerals and hormones, and also serves as an anticoagulant and antioxidant. There are approximately 6 long-chain fatty acid binding sites on BSA, with the strongest three located in each domain.
"Bovine serum albumin is more than just a protein, it is a bridge between laboratory research and biological mechanisms."
Application
BSA is often used as a model for other serum albumins, especially human serum albumin, with a structural homology of up to 76%. In biochemical applications, including enzyme-linked immunosorbent assays (ELISAs), western blotting, and immunohistochemistry, BSA is often used as a stimulant or inhibitor. In immunohistochemistry, tissue sections are often incubated with BSA blocking agents to bind non-specific binding sites, which can improve the specificity of the antibody for the antigen and make the experimental results more accurate.
BSA is also used as a nutrient in cell and microbial culture. During restriction enzyme digestion, BSA stabilizes some digested enzymes and prevents them from adhering to reaction tubes, pipette tips, and other containers. More interestingly, BSA is often used to determine the amount of other proteins by comparing the amount of unknown protein to the known amount of BSA (e.g. Bradford Protein Assay).
"BSA is popular for its non-impact and cost-effectiveness in multiple biochemical reactions."
In addition, another use of BSA is to temporarily isolate substances that hinder the activity of certain enzymes, which usually affects the performance of the polymerase chain reaction (PCR). BSA has also been widely used in synthesizing nanostructures and evaluating the toxic or beneficial effects of metal ions and their complexes, undoubtedly promoting research in many fields.
In short, bovine serum albumin is undoubtedly an indispensable "universal assistant" in scientific research. Its diversity and wide range of applications allow it to play a key role in laboratory research. So, what new undiscovered BSA applications will there be in the future?
