Bovine Serum Albumin (BSA) is universal in the lab, having use in Western blot, cell tissue culture, PCR and more, but BSA’s versatility has led researchers to ask many common questions. Rather than chasing answers through the Internet, we have identified 6 very common questions regarding BSA and provided some very detailed answers to serve as a helpful guide.

1. What Type of BSA Should I Use for My Experiment?

In our earlier article on this very topic we actually addressed this question in greater detail. This question comes up often because there are so many types of BSAs available which are directed toward a wide range of laboratory applications, each having characteristics that better optimize it for a lab technique. For instance, you need a blocking agent, you might want a BSA product that’s specifically certified as globulin- or IgG-free to minimize nonspecific binding from potential serum protein contaminants.

Deciding on which BSA to use will be based on the type experiment you’re doing and your specific needs. After taking a look at the above mentioned article and its selection guide table, it’s still good to refer to other sources such as ResearchGate for more information and a more tailored answer.




2. How Does BSA Work as a Blocking Agent?

Blocking agents are meant to prevent the nonspecific binding of your antibodies. In general, as long as a protein doesn’t have affinity for your probe, it can theoretically be used as a blocking agent. But if you choose anything at random, your experiment will likely be inefficient. Therefore, there are certain proteins that are directed for this type of work. These proteins bind more consistently to the membrane, improving assay sensitivity and reducing background interference.

So why BSA then? First of all, you don’t want just any BSA. Some BSA grade preparations may contain trace amount of serum globulins or other contaminants, which can lead to nonspecific binding. For blocking purposes, using BSA that listed as globulin-free minimizes risk.

While BSA is primarily used as a blocking agent in Westerns, it's also sometimes used as a blocking agent for sensitive in vitro protein activity assays. Proteins can stick to plastic pipette tips, centrifuge tubes, and other items. By including an excess of BSA in these reactions, the BSA can stick to the pipette tips, tubes, and other plastic items, preventing the protein of interest from sticking. Keeping your protein of interest from binding to the plastic enables more quantitative measurement of protein activity.




3. Should I Use BSA or Milk for My Western Blot?

The two most frequently used blocking agents in labs are nonfat milk and BSA. And there are pros and cons to each. Milk is usually more affordable and easily prepared from powder compared to BSA; however, milk is not good to use in avidin-biotin systems since milk contains biotin, and milk should not be used on phosphorylated proteins.

Typically, when working with phosphorylated proteins, BSA tends to work better as a blocking agent. This is because milk has a variety of proteins, one being phosphoprotein casein, which leads to a higher background. Of course with all advice, there are special cases. The best rule of thumb when working with phosphorylated proteins is to start with BSA, and then optimize from there.






4. Why Does Protein Concentration Estimation Usually Require BSA?

In order to estimate the protein concentration of an unknown sample, you need to compare it to a reference that is most similar to your sample. However, this isn’t always easy to find, so BSA plays the role of reference. There are a few factors that make BSA an appropriate reference to use: it’s very abundant, it’s very affordable, it retains stability under normal lab conditions while remaining largely inert in many biochemical reactions.





5. Is Bovine Serum Albumin (BSA) and Fetal Bovine Serum (FBS) the Same Thing?

Nope. It’s not the same. Fetal Bovine Serum is a commonly used serum supplement for eukaryotic cell culture. The benefit of FBS for cell culture is its lower antibody levels and higher growth factor levels. Bovine Serum Albumin (BSA) is used in a variety of laboratory applications including its function as a protein concentration standard, its function as a cell nutrient and its ability to stabilize enzymes during restriction digest. The important takeaway here, however, is that while they often both come up in Google searches when you’re only looking for one or the other, and sound very similar, they are indeed different.





6. Why is It Important for BSA to Be Manufactured in the USA?

Sourcing BSA from countries classified as having negligible or controlled BSE risk, such as the US and New Zealand helps ensure product safety.

GoldBio particularly stresses that our BSA is made in the United States or New Zealand in a closed loop system, and is certified to be BSE/TSE free.



Karen Martin
GoldBio Marketing Coordinator

"To understand the universe is to understand math." My 8th grade
math teacher's quote meant nothing to me at the time. Then came
college, and the revelation that the adults in my past were right all
along. But since math feels less tangible, I fell for biology and have
found pure happiness behind my desk at GoldBio, learning, writing
and loving everything science.


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