Ali Kakeshpour - Department of Chemistry, University of Tehtan, Tehtan, Iran
Fatemeh Pirani - Department of Chemistry, University of University of Zabol, Zabol, Iran

This century has been an adventure for biochemists to understand protein folding and biomolecularinteractions using NMR and X-ray spectroscopy methods.1,2 Quantum chemical methods, as acompliment to experiment, offer a deeper insight into understanding structural and energetic featuresinteraction and folding phenomenon.3 The large size of biomolecules, however, limits the applicability ofbenchmark methods used in small molecule systems. Semi-empirical methods, which use Hartree-Fockformalism with approximations driven from experimental data, are one solution to this problem bydecreasing the cost of calculations substantially. In this research and our studies, we assess the ability ofsemi-empirical4 methods in predicting the energy profile of pi-conjugated systems and their derivatives.These interactions are important since they determine secondary, tertiary and quaternary structures ofproteins by determining the amide geometry, i.e. the out-of-plane twist. Based on the research we canstudy these interactions by computational chemistry which leads to Careful examination interactions.

Pi-Conjugation; Quantum Chemistry; Semi-empirical