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 might want an IgG free BSA if you need a blocking agent.

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. Many types of BSAs contain IgGs (ok for other applications) which can lead to nonspecific binding. The goal is to work with a protein that will keep your experiment in optimal conditions, so in the case of a blocking agent, particularly BSA, you want to consider types that are free of immunoglobulins.

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’s very stable and it won’t have a huge impact in 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 the It Important for BSA to Be Manufactured in the USA?

The importance of sourcing your BSA from either the US or Australia is due to concern about the prion infection bovine spongiform encephalitis (BSE). There has not been an outbreak in the United States which makes these products more trustworthy. GoldBio particularly stresses that their BSA is made in the United States in a closed loop system from USDA inspected animals, and is certified to be BSE/TSE free.

Have additional questions? Email [email protected]

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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