Bovine Serum Albumin, commonly known as BSA, is a protein frequently encountered in scientific research and various industrial applications. Originating from cows, it is a significant component of their blood plasma. Its widespread use in laboratories stems from its stable nature, consistent properties, natural abundance, and ease of purification.
What is Bovine Serum Albumin?
Bovine Serum Albumin is a globular protein derived from the blood of cows. It accounts for a substantial portion of the protein content in bovine blood plasma, acting as a major circulating protein. It is synthesized in the liver and then secreted into the bloodstream.
BSA is a soluble, single-chain protein composed of 583 amino acid residues. Its structure includes three homologous domains, each further divided into two subdomains. These structural features contribute to its ability to bind various molecules and maintain stability. The protein also contains 17 intramolecular disulfide bonds, which are important for maintaining its compact shape.
Understanding Kilodaltons and BSA’s Molecular Weight
A kilodalton (kDa) is a unit of molecular mass, frequently used to express the size of large molecules like proteins and polysaccharides. One kilodalton is equivalent to 1,000 daltons, and a single dalton represents one-twelfth of the mass of a carbon-12 atom. This unit provides a convenient way to quantify molecular mass.
Bovine Serum Albumin has a precisely known molecular weight of approximately 66.5 kilodaltons (kDa), or 66,463 Daltons. This specific and consistent molecular weight makes BSA an ideal molecular weight standard in laboratory techniques. For instance, in gel electrophoresis, BSA’s known size serves as a reference point, allowing scientists to estimate the sizes of unknown proteins by comparing their migration patterns to that of BSA.
Key Applications of BSA
Bovine Serum Albumin is widely utilized across various scientific disciplines due to its unique properties, including its high solubility, stability, and ability to avoid non-specific interactions. One common application is its use as a blocking agent in immunoassays like ELISA and Western blotting. In these techniques, BSA coats surfaces to prevent antibodies from binding to unintended sites, reducing background noise and improving result accuracy.
BSA also serves as a reliable protein standard for quantifying protein concentrations in samples. Its consistent purity and known molecular weight allow researchers to create standard curves, which are then used to determine the amount of protein in unknown samples.
BSA is frequently added to cell culture media as a nutrient supplement. It helps bind and deliver essential molecules such as fatty acids and hormones to cultured cells, promoting their growth and survival, especially in serum-free conditions.