Stable conformers of 1.-serine were automatically explored by applications of the scaled hypersphere search (SHS) method to equilibrium structures maintaining the chemical bond skeletons of serine. Energy barriers for conformational changes of L-serine were estimated from the heights of obtained transition structures. Zero-point-corrected electronic energies and Gibbs free energies of the 24 lowest energy conformers and 21 transition structures were calculated at 100, 298, and 400 K by a composite quantum chemistry method (Gaussian -4). Relative populations of 24 conformers including nine new conformers were calculated from the Gibbs energies assuming thermal equilibrium. (C) 2016 Elsevier B.V. All rights reserved.