The conformational landscape of the tripeptide Gly-L-Tyr-Gly with protected N- and C- termini has been explored by using a genetic algorithm combined with DFT and MP2 calculations in order to investigate all potential minima on its potential energy surface (PES). The genetic algorithm based on the Multi-Niche Crowding (MNC) technique was used to generate a set of most probable equilibrium structures for the title compound. Resulting structures will then be submitted to an hierarchy of increasingly more accurate electronic structure calculations (single-point HF/3-21G* energy calculation, HF/6-31+G(d) geometry optimization, B3LYP/6-311++G(2d,2p) geometry optimization and MP2/6-311++G(2d,2p) single-point energy calculation). The developed procedure was tested by comparing the obtained results (stabilities, geometrical parameters and relative energies of localized conformers) with those derived from a commonly used ordinary optimization strategy. Our method was able to predicted 18 conformations among 28 localized by the ordinary strategy and in which the 11 most stables ones are in the same stability order. The comparison of 18 common conformation geometries revealed nearly perfect linear adjustments with R2 values of 0.9996, 0.9992, 0.9988, and 0.9988 for dihedral angles φtyr, ψtyr, χ1 and χ2 respectively. Relative energies of the matching 18 conformers also fitted to a linear plot with an R2 value of 0.9962.
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