Protein Adsorption into Mesopores: A Combination of Electrostatic Interaction, Counterion Release and van der Waals Forces

TL;DR

This study investigates how bovine cytochrome c adsorbs into mesoporous silica SBA-15, revealing that electrostatic, van der Waals, and counterion release forces all influence protein binding, challenging the simple electrostatic interaction model.

Contribution

It provides a detailed analysis of multiple interaction forces involved in protein adsorption into mesopores, highlighting the complex nature of these interactions.

Findings

Electrostatic, van der Waals, and counterion release forces all contribute to adsorption.

The adsorption behavior varies with pH and ionic strength.

The simple electrostatic model is insufficient to explain the adsorption mechanisms.

Abstract

Bovine heart cytochrome c has been immobilized into the mesoporous silica host material SBA-15 in both its native folded and urea-unfolded state. The comparison of the two folding states' behavior casts doubt on the commonly used explanation of cytochrome c adsorption, i.e. the electrostatic interaction model. A detailed investigation of the protein binding as a function of pH and ionic strength of the buffer solution reveals the complex nature of the protein-silica interaction. Electrostatic interaction, van der Waals forces and entropic contributions by counterion release each contribute to adsorption on the silica pore walls.