Light scattering study of complex formation between protein and polyelectrolyte at various ionic strengths

Area of Science:

• Biophysical Chemistry
• Polymer Science
• Protein-Polyelectrolyte Interactions

Background:

• Protein-polyelectrolyte complexes (PPCs) are crucial in various biological and industrial applications.
• Understanding the electrostatic interactions between proteins and charged polymers is essential for controlling complex formation.
• Bovine serum albumin (BSA) and potassium poly (vinyl alcohol) sulfate (KPVS) were chosen as model systems.

Purpose of the Study:

• To investigate the formation of PPCs between BSA and KPVS at pH 3.
• To determine the effect of ionic strength on the properties of these complexes.
• To elucidate the charge characteristics and structural behavior of BSA-KPVS complexes.

Main Methods:

• Turbidimetric titration was used to monitor complex formation.
• Dynamic Light Scattering (DLS) determined particle size.
• Electrophoretic Light Scattering (ELS) estimated the formal charge of the PPCs.

Main Results:

• Formal charge of PPCs (Z(PPC)) was estimated using free-draining and non-free-draining models.
• Comparison of experimental Z(PPC) with theoretical calculations based on BSA and KPVS charges.
• Evidence suggests PPCs behave as free-draining molecules at high ionic strength.

Conclusions:

• PPC formation between BSA and KPVS at low ionic strength follows a 1:1 charge neutralization stoichiometry.
• The study provides insights into the electrostatic interactions governing protein-polyelectrolyte complexation.
• Electrophoretic behavior of BSA-KPVS complexes is influenced by ionic strength.