The evaluation and validation of copper (II) force field parameters of the Auxiliary Activity family 9 enzymes

•Force field parameters for Cu2+ have been determined for the active site of AA9.•Two sets of van der Waals values separately describe the Cu2+ to oxygen interaction.•Two separate molecular dynamics simulations include solvent, AA9 and β-cellulose.•Biased and unbiased dynamics show motion and binding of AA9 to the cellulose.•Biased dynamics accelerate the observation of both of these processes.