Spatial distribution of protein molecules adsorbed at a polyelectrolyte multilayer

Area of Science:

• Materials Science
• Biophysics
• Surface Chemistry

Background:

• Understanding protein adsorption onto polyelectrolyte multilayers is crucial for biomaterial development.
• The spatial distribution and interaction mechanisms of proteins at interfaces remain key research areas.

Purpose of the Study:

• To determine the spatial distribution of Staphylococcal nuclease (SNase) within a planar polyelectrolyte multilayer.
• To investigate the influence of temperature and solution pD on SNase adsorption and penetration.

Main Methods:

• Neutron reflectometry with contrast variation was employed to analyze protein density profiles.
• Staphylococcal nuclease (SNase) was adsorbed onto a poly(ethylene imine)/poly(styrene sulfonate)/poly(allylamine hydrochloride) multilayer at varying temperatures (22°C, 42°C) and pD values (4.9, 7.5).

Main Results:

• SNase was found to partially penetrate the polyelectrolyte multilayer under all studied conditions.
• Penetration depth varied with pD, with greater penetration observed at pD 4.9 (50 Å) compared to pD 7.5 (25 Å).
• Increasing temperature enhanced overall protein adsorption, with a more pronounced increase in multilayer penetration at higher protein charge (pD 4.9) and accumulation at the interface at lower charge (pD 7.5).

Conclusions:

• Protein adsorption onto polyelectrolyte multilayers is influenced by both electrostatic interactions and entropic driving forces.
• The observed penetration of SNase into the multilayer suggests a complexation mechanism driven by entropy, likely involving counterion release.