Energetics and Mechanism of Desorption of Small Molecules From Cellulose Crystal Surface: Atomic Force Microscopy (AFM) and Molecular Simulation Study

The cello-oligosaccharide intermediates formed during enzymatic hydrolysis of cellulose are adsorbed on the cellulose crystal surface thus hindering further action of the enzyme.  In this work, we have used a combination of AFM experiments and molecular modeling to decipher both the energetics and mechanism of the process of desorption of cello-oligosaccharide molecules from the cellulose crystal surface. For this purpose, molecules of model compounds containing different functional groups are attached to the AFM tip and the adhesion force between these molecules and the cellulose crystal surface is determined using AFM experiments.  The steered molecular dynamics (SMD) technique is used to determine the adhesion force as well as the mechanism of desorption of these same molecules from the cellulose crystal surface.  Simulation results obtained for different crystal surfaces as well as for varying number of adsorbed molecules are directly compared with AFM experiment results.