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Dissimilar pH-dependent adsorption features of bovine serum albumin and α-chymotrypsin on mica probed by AFM

2009; Elsevier BV; Volume: 70; Issue: 2 Linguagem: Inglês

10.1016/j.colsurfb.2008.12.036

1873-4367

Sandrine Demanèche, Jean‐Paul Chapel, L. Jocteur Monrozier, Hervé Quiquampoix,

Polymer Surface Interaction Studies

We studied bovine serum albumin (BSA) and alpha-chymotrypsin adsorption onto mica surfaces over a large pH range by atomic force microscopy (AFM) measurements in liquid. Data analyses (height, roughness and roughness factor) brought new insights on the conformation of proteins in soil environments, with mica as a model of soil phyllosilicates and non-hydrophobic surfaces. Validation of AFM approach was performed on BSA, whose behavior was previously described by nuclear magnetic resonance and infra-red spectroscopic methods. Maximum adsorption was observed near the isoelectric point (IEP). A stronger interaction and a lower amount of adsorbed proteins were observed below the IEP, which contrasted with the progressive decrease of adsorption above the IEP. We then studied the adsorption of alpha-chymotrypsin, a proteolytic enzyme commonly found in soils. AFM pictures demonstrated a complete coverage of the mica surface at the IEP in contrast to the BSA case. Comparison of the AFM data with other indirect methods broadened the understanding of alpha-chymotrypsin adsorption process through the direct display of the protein adsorption patterns as a function of pH.