Figure 1.

Molecular dynamics simulations of PrP^C at low and neutral pH. (a) The rms deviation from the starting NMR structure as a function of simulation time. (b) The rms fluctuation of the α-carbons about their mean structure during the last 2.5 ns of the simulations. (c) The main chain folds every 0.5 ns over the 10-ns simulations at neutral and low pH. The protein is dynamic, particularly in the turns and loop regions, but the overall structure is well maintained at neutral pH. In contrast, at low pH conformational transitions and fluidity span almost the entire sequence but are particularly prominent at the N terminus and HA.