1-4 interaction scaling factors are used in AMBER forcefields to reduce the exaggeration of short-range repulsion caused by the 6-12 Lennard-Jones potential and a nonpolarizable charge model and to obtain better agreements of small-molecule conformational energies with experimental data. However, the effects of these scaling factors on protein secondary structure conformations have not been investigated until now. This article reports the finding that the 1-4 interactions among the protein backbone atoms separated by three consecutive covalent bonds are more repulsive in the alpha-helix conformation than in two beta-strand conformations. Therefore, the 1-4 interaction scaling factors of protein backbone torsions phi and psi control the conformational equilibrium between alpha-helix and beta-strand. Molecular dynamics simulations confirm that reducing the phi and psi scaling factors readily converts the alpha-helix conformation of AcO-(AAQAA)(3)-NH2 to a beta-strand conformation, and the reverse occurs when these scaling factors are increased. These results suggest that the phi and psi scaling factors can be used to generate the alpha-helix or beta-strand conformation in situ and to control the propensities of a forcefield for adopting secondary structure elements. (C) 2014 The Author. Published by Elsevier Inc.