We observed slow convergence of dihedral angle distributions and/or scalar couplings for some of the dipeptides. In particular we aimed for all systems to have uncertainties no larger than ∼0.01 in terms of predicted probabilities of backbone conformational states and ∼0.1 Hz in terms of predicted scalar couplings. For these systems (ff99SB: T1P and TPO; FB18: SER, THR, Y1P, and PTR) we performed replica exchange MD (REMD) simulations to improve the conformational sampling. The REMD protocol consisted of running 20 replicas in exponentially spaced temperatures between 303.15 K and 410 K.