RESUMEN
We report here two new small-size peptides acting as modulators of the ß-site APP cleaving enzyme 1 (BACE1) exosite. Ac-YPYFDPL-NH2 and Ac-YPYDIPL-NH2 displayed a moderate but significant inhibitory effect on BACE1. These peptides were obtained from a molecular modeling study. By combining MD simulations with ab initio and DFT calculations, a simple and generally applicable procedure to evaluate the binding energies of small-size peptides interacting with the exosite of the BACE1 is reported here. The structural aspects obtained for the different complexes were analyzed providing a clear picture about the binding interactions of these peptides. These interactions have been investigated within the framework of the density functional theory and the quantum theory of atoms in molecules using a reduced model. Although the approach used here was traditionally applied to the study of noncovalent interactions in small molecules complexes in gas phase, we show, through in this work, that this methodology is also a very powerful tool for the study of biomolecular complexes, providing a very detailed description of the binding event of peptides modulators at the exosite of BACE1.