Dimerization Of Bovine Serum Albumin As Evidenced By Particle Size And Molecular Mass Measurement

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. Phosphate-buffered saline (PBS) is a water-based salt solution which is isotonic to mammalian cells and stabilizes the pH at neutral values (commonly pH 7.4). This buffer is widely used to dissolve proteins, resuspend cells or as transport solution for biological samples.

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 PBS. We then compared the particle size and molecular mass values returned by the Litesizer™ particle analyzer for the two BSA solutions.