Dimerization of Bovine Serum Albumin As Evidenced By Particle Size and Molecular Mass Measurement

Preparation methods have a large influence on the folding and oligomerization behavior of proteins in solution. Here we compared bovine serum albumin (BSA) dissolved in deionized water (BSA-H2O) to BSA resuspended in isotonic buffer (BSA-PBS). Particle size results returned by the Litesizer™ suggested that BSA-H20 had suffered denaturation and/or aggregation, while BSA-PBS primarily consisted in native BSA dimers. Molecular mass measurements on BSA-PBS displayed the expected molecular mass of dimeric BSA. The Litesizer™ is therefore a useful tool for the optimization of sample preparation and the quality control of proteins.

Bovine serum albumin (BSA) is a small, stable and moderately non-reactive protein which is commonly used in the lab as protein concentration standard, as blocker in a variety of immunoassays or as cell culture supplement. Being the most abundant serum protein in bovine blood, which is a byproduct of the cattle industry, BSA is a relatively cheap and easily accessible compound. 

According to the literature, BSA has a nominal size of 7.1 nm and a molecular mass of 66.5 kDa. Bovine serum albumin shows a natural tendency to dimerize under stress conditions, with BSA dimers displaying a molecular mass of 132 kDa.

In order to highlight the influence of sample preparation methods on the structure of the solubilized protein, we dissolved purified BSA either in deionized water or in the isotonic buffer PBS. We then compared the particle size and molecular mass values returned by the Litesizer™ particle analyzer for the two BSA solutions.

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