What is Bovine Serum Albumin (BSA)?

by Simon Currie

If any protein embodies the phrase “jack of all trades,” it is surely bovine serum albumin (BSA). Albumin is an ace of its own biologically-relevant trade as well, but ideal molecular properties have vaulted this protein into being coopted as a versatile reagent for a number of important biochemical and biological experiments.  

Bovine serum albumin (BSA) is an abundant, stable, and water-soluble protein extracted from cow blood plasma. Serum albumin has important biological roles, and BSA is a versatile and useful tool in the life sciences.

In this article we’ll cover the basics of what BSA is and why it is so frequently used in lab experiments.

In this article:

What are the biological roles of serum albumin?

Why is bovine serum albumin so popular?

What is bovine serum albumin used for?

What are the biological roles of serum albumin?

Serum albumin is the most abundant protein found in the blood plasma of vertebrate animals. It plays a critical role in maintaining osmotic pressure, balancing the fluid between blood vessels and our tissues (Michelis et al, 2016). When serum albumin levels are too low, fluid leaks out of our bloodstream and into our tissues, causing edema. This is why albumin levels are tested as part of the normal blood panel during your annual physical.

Besides maintaining fluid in the blood stream, albumin binds to numerous substances such as fatty acids, natural hormones, and other small molecules, and helps distribute them throughout your body (Figure 1) (Jacobsen, 1969; Jayaraj et al, 2021; Spector, 1975; Sudlow et al, 1975).

Figure 1. Albumin binds to small molecules such as fatty acids, natural hormones, and drugs, and helps distribute them throughout your body (Berman et al, 2000; Majorek et al, 2012).

The affinity of each of these molecules for albumin is relatively weak, but as we’ll discuss in the next section the concentration of albumin is really high in blood, which drives binding between albumin and each of these small molecules. Binding to albumin is even a design strategy when developing new drugs to increase the drug’s longevity in the bloodstream and therefore its bioavailability to the relevant tissue (Larsen et al, 2016).

Why is bovine serum albumin so popular?

BSA is the albumin of choice for most lab experiments. Albumin is very abundant; its concentration is roughly 30 mg/mL in cow’s blood, making up approximately 40% of the total proteins in cow serum (Figure 2) (da Fonseca et al, 2025).

Figure 2. Albumin is the most abundant protein in blood serum. In this representation, IgG is the only other protein with at least one copy for the given volume (Harris et al, 1998; Perrin, 2014).

High albumin concentration is not unique to cows, however, it is present at similarly high concentrations in other species such as humans and mice as well (Lausted et al, 2008). This conserved high concentration makes sense given the important biological roles for albumin above.

The prevalent use of cows in other industries makes BSA relatively affordable with excellent availability relative to albumin from other species. In the next section we’ll discuss some of the different purposes that albumin is used for in lab. In general, anytime you’re using albumin as a blocker, stabilizer, or standard, you’ll usually want to use the more affordable BSA instead of recombinant human albumin.

What is bovine serum albumin used for?

Albumin’s high stability, and water-solubility contribute to its abundance and biological functions, and those same features make BSA a convenient tool in a variety of different experiments, including:

·         As a blocking agent in Western blots and other detection assays

·         To stabilize enzymes and prevent non-specific binding to lab plastic

·         As a standard for measuring the concentration of your protein of interest

·         Providing nutrients in serum-free and reduced-serum cell culture

GoldBio carries a number of different versions of BSA, each with different strengths and uses. All of our BSA products are reliable and affordable tools for powering your research experiments. Check out the product links below, as well as additional articles on BSA to learn more.

References

Berman, H. M., Westbrook, J., Feng, Z., Gilliland, G., Bhat, T. N., Weissig, H., Shindyalov, I. N., & Bourne, P. E. (2000). The Protein Data Bank. Nucleic acids research, 28(1), 235–242. https://doi.org/10.1093/nar/28.1.235

COHN, E. J., & STRONG, L. E. (1946). Preparation and properties of serum and plasma proteins; a system for the separation into fractions of the protein and lipoprotein components of biological tissues and fluids. Journal of the American Chemical Society, 68, 459–475. https://doi.org/10.1021/ja01207a034

da Fonseca, L. A., Montiani-Ferreira, F., Rodriguez, M., Bittar, J. H. J., Girardi, F. M., Moraes, T. M. A., & Cray, C. (2025). Measurement of bovine (Bos taurus) serum albumin by different methods and the comparison of protein fractions determined by capillary zone electrophoresis and agarose gel electrophoresis. PeerJ, 13, e19685. https://doi.org/10.7717/peerj.19685

Harris, L. J., Skaletsky, E., & McPherson, A. (1998). Crystallographic structure of an intact IgG1 monoclonal antibody. Journal of molecular biology, 275(5), 861–872. https://doi.org/10.1006/jmbi.1997.1508

Jacobsen J. (1969). Binding of bilirubin to human serum albumin - determination of the dissociation constants. FEBS letters, 5(2), 112–114. https://doi.org/10.1016/0014-5793(69)80307-8

Jayaraj, A., Schwanz, H. A., Spencer, D. J., Bhasin, S., Hamilton, J. A., Jayaram, B., Goldman, A. L., Krishna, M., Krishnan, M., Shah, A., Jin, Z., Krenzel, E., Nair, S. N., Ramesh, S., Guo, W., Wagner, G., Arthanari, H., Peng, L., Lawney, B., & Jasuja, R. (2021). Allosterically Coupled Multisite Binding of Testosterone to Human Serum Albumin. Endocrinology, 162(2), bqaa199. https://doi.org/10.1210/endocr/bqaa199

Larsen MT, Kuhlmann M, Hvam ML, Howard KA. Albumin-based drug delivery: harnessing nature to cure disease. Mol Cell Ther. 2016 Feb 27;4:3. doi: 10.1186/s40591-016-0048-8. PMID: 26925240; PMCID: PMC4769556.

Lausted, C., Hu, Z., & Hood, L. (2008). Quantitative serum proteomics from surface plasmon resonance imaging. Molecular & cellular proteomics : MCP, 7(12), 2464–2474. https://doi.org/10.1074/mcp.M800121-MCP200

Majorek, K. A., Porebski, P. J., Dayal, A., Zimmerman, M. D., Jablonska, K., Stewart, A. J., Chruszcz, M., & Minor, W. (2012). Structural and immunologic characterization of bovine, horse, and rabbit serum albumins. Molecular immunology, 52(3-4), 174–182. https://doi.org/10.1016/j.molimm.2012.05.011

Michelis, R., Sela, S., Zeitun, T., Geron, R., & Kristal, B. (2016). Unexpected Normal Colloid Osmotic Pressure in Clinical States with Low Serum Albumin. PloS one, 11(7), e0159839. https://doi.org/10.1371/journal.pone.0159839

Perrin, A. J. (2015). Identification and characterisation of host-pathogen protein-protein interactions in the blood stages of malaria [Doctoral dissertation, University of Cambridge]. Apollo - University of Cambridge Repository. https://www.repository.cam.ac.uk/items/914ad5f5-db23-4802-8025-ea5d697b7ceb

Spector A. A. (1975). Fatty acid binding to plasma albumin. Journal of lipid research, 16(3), 165–179.

Sudlow, G., Birkett, D. J., & Wade, D. N. (1975). The characterization of two specific drug binding sites on human serum albumin. Molecular pharmacology, 11(6), 824–832.

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