Hydration and interactions in protein solutions containing concentrated electrolytes studied by small-angle...

Area of Science:

• Biophysics
• Protein Science
• Solution Chemistry

Background:

• Proteins in concentrated salt solutions are crucial for crystallization and purification.
• Understanding protein-solution interactions, including hydration and salt effects, is vital but complex.
• The interplay between hydration shells, salt ions, and protein interactions requires fundamental investigation.

Purpose of the Study:

• To investigate the behavior of bovine serum albumin (BSA) in concentrated salt solutions using small-angle neutron scattering (SANS).
• To quantify the hydration shell of BSA and its effect on protein-protein interactions.
• To compare SANS results with previous small-angle X-ray scattering (SAXS) data.

Main Methods:

• Small-angle neutron scattering (SANS) was employed to study bovine serum albumin (BSA) in various salt solutions.
• Guinier analysis of SANS data was used to determine the forward intensity I(0) and the second virial coefficient (A(2)).
• SANS data across the full q-range were analyzed using liquid theoretical approaches.

Main Results:

• SANS determined a BSA volume approximately 37% smaller than SAXS, indicating a hydration shell of 0.30 g/g.
• The second virial coefficient (A(2)) demonstrated an inverse relationship with the Hofmeister series.
• Dimensionless coefficient B(2), corrected for hydration and non-spherical shape, provided a better description of protein interactions.

Conclusions:

• BSA's hydration shell significantly influences its interactions in concentrated salt solutions.
• The study provides a more accurate model for protein interactions by incorporating hydration and shape corrections.
• SANS is a powerful tool for characterizing protein behavior in solution, complementing SAXS.