Analyzing Bovine Serum Albumin with Dynamic Light Scattering

Dynamic light scattering (DLS) is an instrumental technique that allows researchers to measure the size of nanoparticles and biological macromolecules, such as proteins. The technique utilizes Brownian motion, the random movement of particles due to collisions with solvent molecules. As light from a laser hits the moving particles, the intensity of light that hits the detector fluctuates. Smaller particles diffuse faster in solution, leading to greater intensity fluctuations, while larger particles diffuse slower in solution, leading to smaller intensity fluctuations. For well-studied proteins, such as bovine serum albumin (BSA), DLS measurements show particle sizes of about 7.5 nanometers (nm). Denaturing proteins with high-temperature environments unfolds their three-dimensional structure, increasing their particle size. Previous studies show that these shifts in particle size can be reflected through DLS measurements. To see these shifts in particle size, we heat-treated BSA and analyzed a mixture of heat-treated and native (not heat-treated) BSA. The DLS measurement for the mixture resulted in two peaks: a larger peak at 21.5 nm, corresponding to the heat-treated BSA, and a smaller peak at 5.6 nm, corresponding to the native BSA. Ultimately, the aim of this project was to work with a well-understood protein like BSA and apply the methods learned towards a less-understood protein.