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In complexation reactions, metal cations are the electron pair acceptors, and the ligands are the electron pair donors. The stability of the metal complexes depends primarily on the complexing ability of the central metal ion and the nature of the ligands. Generally, the complexing ability of the metal ion depends on the size and charge of the ion. As the metal ion size increases, the stability of the metal complexes decreases, provided that the valency of the metal ion and the ligands remain...

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Assembly and Characterization of Polyelectrolyte Complex Micelles

Assembly and Characterization of Polyelectrolyte Complex Micelles

Published on: March 2, 2020

Structural study of coacervation in protein-polyelectrolyte complexes.

S Chodankar¹, V K Aswal, J Kohlbrecher

¹Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai-400 085, India.

Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics

|October 15, 2008

Summary

This summary is machine-generated.

We studied protein-polyelectrolyte coacervation using bovine serum albumin (BSA) and sodium polystyrene sulfonate (NaPSS). Small-angle neutron scattering revealed complex structures and phase separation influenced by pH, ionic strength, and component ratios.

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Area of Science:

Biophysics
Materials Science
Polymer Science

Background:

Coacervation is a liquid-liquid phase separation process crucial for biological organization.
Understanding protein-polyelectrolyte interactions is key to controlling coacervation for various applications.

Purpose of the Study:

To investigate the coacervation of bovine serum albumin (BSA) with sodium polystyrene sulfonate (NaPSS).
To elucidate the structural evolution during coacervation and the properties of the resulting coacervates under varying solution conditions.

Main Methods:

Small-angle neutron scattering (SANS) was employed to analyze the structure of BSA-NaPSS complexes before and after phase separation.
Turbidity measurements were used to determine the conditions for coacervation, specifically monitoring pH changes.

Main Results:

BSA-NaPSS complexes exhibit a fractal necklace-like structure prior to phase separation.
Coacervation occurs spontaneously below pH 4, forming a hierarchically branched network with two distinct length scales.
Complex structure compactness decreases with increasing pH away from BSA's isoelectric point due to charge repulsion.

Conclusions:

Solution conditions like pH, ionic strength, and component ratio significantly influence BSA-NaPSS coacervation and coacervate structure.
The study reveals insights into the hierarchical self-assembly of protein-polyelectrolyte complexes during phase separation.
A substantial portion of complexes remains in the supernatant, indicating incomplete phase separation under certain conditions.