Özet:

The lowest energy molecular geometry of the Cyclo(Trp-Trp) dipeptide (C₂₂H₂₀N₄O₂), which has important biological activities such as antimicrobial and anticancer, was determined by Density Functional Theory calculations made following theoretical conformation analysis calculation. First, the most probable molecular geometries of the dipeptide were determined with the contribution of Ramachandran maps and sidechain dihedral angles (χ), and the dihedral angles belonging to the eight conformations with the lowest energy were tabulated in comparison with before and after conformation analysis. The total energy of these conformation and van der Waals, electrostatic, hydrogen and torsion energy values contributing to this total energy were calculated. Among these eight conformations, the lowest energy conformer was introduced as the starting data to the Gaussian03 program and optimized at DFT/B3LYP/6-31++G(d,p) level of theory. In addition, the changes in dihedral angles were determined by comparing the lowest energy conformer found as a result of theoretical conformation analysis and optimized molecular geometry.