The effect of deuterium oxide on the conformational stability and aggregation of bovine serum albumin

Protein aggregation is a significant problem affecting the integrity of proteins, and is a major hindrance to the development of biopharmaceutical products. Deuterium oxide (D2O), widely used in protein characterization studies, has been shown to promote protein aggregation when used as a substitute for water in most buffered protein solutions; however, a few studies have reported minor improvements in melting point temperatures for some proteins. Our study aims to investigate the effect of D2O on protein stability, using bovine serum albumin (BSA) as a model. We performed accelerated stability studies at high temperatures and assessed the physical and conformational stability of BSA using fluorescence spectroscopy, dynamic light scattering (DLS) and size-exclusion high performance liquid chromatography. Our findings reveal that D2O enhances the conformational stability of monomeric BSA, reducing monomer loss and formation of small aggregates at high temperatures. There is also an increase in the formation of larger aggregates probed by thioflavin T (ThT), however, the increase is not considered significant based on DLS results. Our findings demonstrate that exchanging water with D2O can improve the stability of proteins in solution, by maintaining the stability of the monomeric form, which may be beneficial for the long-term storage of some biological products.