Bovine Serum Albumin (BSA) | Knowledge Center | Capricorn Scientific

Bovine Serum Albumin (BSA)

BSA for various cell culture applications

Bovine Serum Albumin, also known as "BSA" or "Fraction V", is a protein derived from bovine blood plasma. It is a small, stable, and moderately non-reactive protein, and therefore often used as a blocker in immunohistochemistry. BSA is also the main constituent of Fetal Bovine Serum (FBS) and commonly used as a protein concentration standard in laboratory experiments.

BSA has numerous other biochemical applications, including immunological detection methods such as ELISA (Enzyme-Linked Immunosorbent Assay), Western Blot, and ELISpot. BSA binds to non-specific binding sites and thereby facilitates the antibody coupling with the antigens of interest. Furthermore, BSA is used as a stabilizer or as a supplement to support cell growth in culture, when supplemented to cell culture media. 


Low Interference. Low Background. Our BSA is of the highest purity (typically 99%).


We are experienced in regulatory approvals and can supply you with all documentation needed.


Our BSA protein is characterized by superior solubility & filterability.

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What is Bovine Serum Albumin (BSA)?

Bovine Serum Albumin (BSA): Crystal Structure | Capricorn Scientific
Visualization: Crystal structure of Bovine Serum Albumin (BSA)

General information on BSA

Bovine Serum Albumin (BSA), also known as "Fraction V", is a protein derived from bovine blood plasma and is a byproduct of the food industry. The nickname "Fraction V" is based on the plasma protein extraction method by Cohn, which makes use of the different solubility behavior of the plasma proteins. In this fractionation, BSA represents the fifth fraction and is based on cold ethanol precipitation.

In order to yield the mature BSA protein, the full-length precursor protein (607 amino acids in length) is modified in two steps: First, a signal peptide (18 AAs) is cut off upon secretion. During the second step – that yields the mature BSA protein – an additional 6 amino acids are removed. The final BSA product then contains 583 amino acids.

Bovine Serum Albumin (BSA) has a molecular weight of 66.5 kDa and is considered to be a small protein (140 × 40 × 40 Å).

Applications of BSA

BSA is used as a blocker in immunohistochemistry to bind to non-specific binding sites. When BSA binds to these, it increases the chance that your antibodies will bind only to the antigens of interest. In the same manner, it also decreases the background noise. These two mechanisms are important, as you want to increase your signal-to-noise ratio for best results.

Further, BSA is also used for quantification of other enzymes. Here, the known amount of BSA protein is compared to an unknown amount of your protein of interest (e.g. Bradford protein assay).

Cells marked with fluorescene for further biochemical analysis
Cells marked with fluorescence for further biochemical analysis

BSA has many other biochemical applications, e.g.:

  • Western Blot, IP, and IHC
  • FACS and other detection methods
  • in microbial cultures as a nutrient source
  • for use with restriction enzymes and other proteins/conjugates for stabilization
  • as a carrier protein for conjugates
  • to prevent adhesion of enzymes to vessels and pipette tips
  • to enhance PCR amplification yield
  • vaccine production
  • primary and stem cell culture
  • and many more...

Different BSA grades are suitable for different applications! Depending on the extraction process (e.g., Standard Grade in comparison to Fatty Acid Free), the final BSA product exhibits a different quality and quantity of enzymes, metabolites, peptides, fatty acids, etc.

Please do not hesitate to contact us, should you have any doubts, which BSA grade is the right one for your experimental setup.
Bovine Serum Albumin (BSA) | Capricorn Scientific
Bovine Serum Albumin (BSA) by Capricorn Scientific

BSA characteristics

Bovine Serum Albumin is negatively charged and therefore has chemical binding properties with water, salts, fatty acids, etc., facilitating the transport of substances between the barriers of cells. Further, it can also act as a binding site for toxic substances, making it highly valuable as a supplement to cell culture media, when cell protection is needed.

BSA is highly soluble in water, yet it can also be used to solubilize lipids and proteins (such as sensitive enzymes). When heated (and to some extent even at lower temperatures), BSA coagulates and forms hydrophobic aggregates – a process that is irreversible.

Storage Powder Solution
Temp. +2 to 25 °C +4 °C
Shelf-life 5 years (after production) 2-7 days

Bovine Serum Albumin can be purified in large quantities from bovine blood serum and therefore has a low cost, which makes it one of the most important players in biochemical applications.

Our BSA is a highly soluble white to yellow with tan to green cast lyophilized powder. In solution (up to 30% in deionized water), BSA is clear to slightly hazy and virtually particulate-free.

Tip: Solubilized BSA can also be aliquoted in small volumes and stored at ≤ -15 °C – a good practice to ensure your BSA remains intact when freezing.

Frequently Asked Questions (FAQ)

Which is better for Western Blot: BSA or non-fat dry milk?

This is a question that usually depends on

  1. the financial factor (BSA is more expensive than non-fat dry milk) or
  2. your experimental setup.

When working with phospho-antibodies, it is generally not advised to use non-fat dry milk in your blocking buffer, as it will most likely distort your signal. This is due to the milk protein casein, which can react with said phospho-antibodies. It is recommended to use 5% BSA blocking buffer for this application.

Further, if your antibody shows low levels of binding capacity/specificity (or if the target protein is only available in small amounts within the cell), it is advised to use BSA in your buffer as blocking agent. This is due to the fact that BSA is a purified single-type protein, whereas non-fat dry milk contains a mix of various proteins, which may hinder correct antibody binding.


The Bradford assay is used to determine the quantity of a protein within a solution. It uses Commassie blue staining as the underlying principle, where stained cells reflect a certain wavelength of light.

When a solution is stained with Commassie blue under acidic conditions, you will be able to observe the following states:

  1. brown solution: no detectable proteins
  2. blue solution: Commassie binds to protein
  3. or anything in between (e.g. purple): depends on the amount of protein binding

Now, you do not know the quantity of your protein of interest within a solution. What you do know, is the amount of BSA you put into your reference solution, since BSA is a purified single-type protein.

You can now compare the absorbance of your protein solution with that of your BSA solutions at 595 nm (anionic bound form of the dye). Usually, a highly-concentrated BSA solution is diluted step by step, offering a range of absorbance levels as reference.

It must be noted that Commassie blue can interfere with various cellular compounds, therefore you should do some research on this topic beforehand, to avoid unreliable/false results.

Bovine Serum Albumin (BSA) is a purified single-type protein derived from bovine blood.

Fetal Bovine Serum (FBS), on the other hand, is derived from the bovine fetus and is a complex mixture (1000+ components) of various molecules (e.g. proteins, lipids, carbohydrates, hormones, enzymes, etc.) that includes a large amount of undefined components. Nearly all components are believed to be essential for the well known growth-promoting properties of FBS, which makes it so unique to other bovine sera. Yet, it is important to mention, that BSA is the main component of FBS.

Whereas BSA is often added to cell culture media that are already supplemented with FBS or other sera, it is not possible to eliminate FBS and replace it with BSA entirely.

Instructions for Use

How to prepare a 5% BSA solution (50 ml)
  1. Weigh in 2.5 g of BSA
  2. Add BSA to 40 ml of your buffer (e.g. TBS-Tween or PBS)
  3. Place in 4 °C for 10 minutes
  4. Fill up the volume to 50 ml with your buffer.

After 10 minutes, the BSA should be dissolved (no precipitates). Stirring or mixing is not necessary, yet you can swirl gently if you wish.

  1. Weigh in 2 g of BSA
  2. Add BSA to 15 ml of 1X Nuclear Preparation Buffer
  3. Place in 4 °C for 10 minutes (no stirring/mixing necessary)
  4. Adjust pH to 7.6 using KOH
  5. Add 1X Nuclear Preparation Buffer to 20 ml
  6. Swirl gently

Before you get started, please refer to the instructions of your primary antibody manufacturer, whether to use BSA, non-fat dry milk, or other as blocking agent.

It is common to use up to 3% BSA. Adjust the amount of BSA for the weigh-in accordingly.

  1. Weigh in 1 g of BSA
  2. Add the BSA to 80 ml of 1X TBST
  3. Mix well (preferably using a magnetic stirrer) until you get a clear solution (no precipitates)
  4. Fill up the volume to 100 ml with 1X TBST
  5. Store at 4 °C and use fresh (up to 5 days)

For long-term storage at -80 °C, you can prepare larger volumes and aliquot in small amounts. The blocking buffer will remain intact up to several months. Using aliquots will avoid unnecessary freeze-thaw cycles.

Browse our BSA products

Bovine Serum Albumin (BSA), Standard Grade

Bovine Serum Albumin (BSA) is a protein derived from bovine blood. It is used in fields like cell culture, molecular biology, protein biochemistry, and detection techniques.
50 g
+2°C to +8°C
€99.00 View Details

Bovine Serum Albumin (BSA), Fatty Acid Free (BSA FAF)

Bovine Serum Albumin (BSA), Fatty Acid Free (BSA FAF) is a protein derived from bovine blood. It is used in fields like cell culture, molecular biology, protein biochemistry, and detection techniques.
50 g
+2°C to +8°C
€169.00 View Details

Bovine Serum Albumin (BSA), Protease Free (BSA PF)

Bovine Serum Albumin (BSA) Protease Free (BSA PF), is a protein derived from bovine blood. It is used in fields like cell culture, molecular biology, protein biochemistry, and detection techniques.
50 g
+2°C to +8°C
€119.00 View Details


  • High purity for low interference & background
  • Regulatory-approved proprietary collection system
  • Superior solubility & filterability
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Find all downloads for our BSA products, such as Safety Data Sheets (SDS) and product infos.

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Cat. No.: BSA-1U | Volume: 50 g | 50%-off Sample; Price: € 31.00
Cat. No.: BSA-PF-1U | Volume: 50 g | 50%-off Sample; Price: €54.50
Cat. No.: BSA-FAF-1U | Volume: 50 g | 50%-off Sample; Price: €72.50

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