The ABEEM/MM (the Atom-bond electronegativity equalization method fused into molecular mechanics) model that explicitly includes the lone pairs and conjugate fluctuating charges is employed to study the peptide conformations. The non-bond direction charge transfers were allowed in some important cases. With the optimized parameters from the alanine dipeptide, the dipole moment, the binding energies and the hydrogen bond lengths of the molecule clusters calculated by the ABEEM/MM model agree well with the corresponding ab initio results. The improved model provided more reasonable structures and con-formational potential of the alanine dipeptide, alanine tetrapeptide and glycine tripeptide than the previous model and other models listed in this paper.

Key words: Atom-bond electronegativity equalization fused into molecular mechanic, polypeptide conformations, anisopolarization, fluctuating charge