BSA and lysozyme adsorption on homoionic montmorillonite: Influence of the interlayer cation

• Adsorption of model proteins on homoionic montmorillonite was investigated.
• Adsorption constants have been obtained by Langmuir model
• Strong influence of interlayer cation on maximum adsorbed amount has been observed.
• The adsorption constants do not follow strictly the Hofmeister series.

This study aims to investigate the influence of interlayer cation alkali metal series (Li+, Na+, K+, Rb+, Cs+) and alkali earth metal (Mg2 +, Ca2 +, Ba2 +) on adsorption of model proteins (lysozyme and bovine serum albumin). The localizations of both proteins and their conformational modifications in the interlayer space of the natural clay mineral were studied by X-ray diffraction, transmission electronic microscopy and fluorescence experiments. Based on Langmuir model isotherms, a strong influence of interlayer cation on maximum adsorbed amount and adsorption equilibrium constant has been observed. However the usual kosmotrope/chaotrope classification cannot be used to describe protein adsorption.