Research paperEffect of ethanol on structures and interactions among globular proteins

- Intermediate-range repulsion and long-range attraction exists among BSA protein with the variation of ethanol concentration.
- In presence of ethanol and NaCl, interaction nature among BSA remains unchanged.
- For lysozyme, intermediate-range repulsion and weak long-range attraction exists in absence of NaCl.
- In presence of NaCl, lysozyme solutions show fractal structure with the variation of ethanol concentration.
- Fractal dimension increases with the increase of ethanol concentration for a fixed protein and salt concentration.

Structures and interactions among globular proteins BSA and lysozyme are explored by small angle neutron scattering (SANS) technique at pD ≈ 7.0 by varying ethanol concentration. Interaction behaviours are also obtained in presence of monovalent salt (NaCl). SANS analysis shows that for both lower and higher BSA concentrations and in presence of NaCl, combination of intermediate-range repulsion and weak long-range attraction is responsible for the effective interaction behaviours with the variation of ethanol concentration. For lysozyme, interaction nature is same as BSA in absence of NaCl but in presence of NaCl, fractal structure factor explains the interaction behaviours.

Fractal structure factor and two-Yukawa potential were used to explain interaction behaviours among proteins in presence of ethanol and NaCl.216