Before revision:  For about two decades, knowledge based potentials based on pairwise distances -- so-called `` potentials of mean force '' (PMFs) -- have been at the central stage in the prediction and design of protein structure and the simulation of protein folding.
After revision:  For about two decades, knowledge based potentials based on pairwise distances -- so-called `` potentials of mean force '' (PMFs) -- have been center stage in the prediction and design of protein structure and the simulation of protein folding.