Stoichiometric Unfolding of Bovine Serum Albumin (Bsa) by Surfactants, from Monomers to Micelles, as Revealed from Hplc/Saxs with On-line Observations of UV-vis Absorption and Refractive Index
Yi-Qi Yeh1*, Kuei-Fen Liao1, Orion Shih1, Wei-Ru Wu1, Chun-Jen Su1, U-Ser Jeng1,2
1National Synchrotron Radiation Research Center, Hsinchu, Taiwan
2Department of Chemical Engineering, National Tsing Hua University, Hsinchu, Taiwan
* Presenter:Yi-Qi Yeh
Detergents are commonly used to disrupt noncovalent interactions of proteins, leading to detergent-protein complex or stabilized recombinant proteins. In past, many methods have been used to investigate conformational changes of proteins and protein-detergent complexes to understand their interactions, polarity and stability in varied detergent concentrations. The local structure of such protein/detergent complex could be resolved by spectroscopies; however, resolving the corresponding stoichiometric protein unfolding conformation requires separating the effects contributed by the coexisted protein/detergent complex and SDS micelles in the solution.
In this work, we show that sodium dodecyl sulfate (SDS), a frequently used surfactant in purification of membrane proteins, can bind to Bovine serum albumin (BSA) for multistage unfolding. The on-line protein purification system of high performance liquid chromatography (SEC-HPLC) incorporated to the beamline 23A synchrotron small-angle X-ray scattering (SAXS) instrument of the Taiwan Light Source at the National Synchrotron Radiation Research Center, allows separating the scattering contributions from the BSA/SDS complexes and SDS micelles; together with on-line observations of UV-vis absorption and refractive index, we resolve the stoichiometric unfolding of BSA by SDS, from the surfactant monomers to micelles.

Keywords: SAXS, protein-detergent complexes, BSA