All biol. ion channels are selectively permeable to specific ions. This mechanism needs to be understood in terms of the interaction of the permeating ions with the surrounding water and protein mols. During the past several years, there have been enormous strides in our understanding of the structure-function relationships in biol. ion channels. Classical MD simulations have been used to investigate the selectivity mechanism, but the importance of polarization effects can hamper an adequate description of the potassium-protein interaction. In this context, quantum mechanics is the ultimate goal of any at. modeling of ionic channels and will help reaching a new level of accuracy and a finer understanding. We have recently developed a QM/MM scheme in which the chem. reactive part of the system can be treated quantum mech. using Car-Parinello mol. dynamics. This method paired with enhanced sampling techniques was used to investigate the mechanism of selectivity displayed by potassium channels. [on SciFinder (R)]