RESUMO
The conformational analysis of N-formyl-D-serine-D-alanine-NH2 dipeptide was studied using density functional theory methods at B3LYP, B3LYPâD3, and M06â2X levels using 6â311 + G (d,p) basis set in the gas and water phases. 87 conformers of 243 stable ones were located and the rest of them were migrated to the more stable geometries. Migration pattern suggests the more stable dipeptide model bears serine in ßL, γD, γL and the alanine in γL and γD configurations. The investigation of sideâchainâbackbone interactions revealed that the most stable conformer, γD-γL, is in the ßâturn region of Ramachandran map; therefore, serine-alanine dipeptide model should be adopted with a ßâturn conformation. Intramolecular hydrogen bonding in ßâturns consideration by QTAIM disclosed γD-γL includes three hydrogen bonds. The computed UVâVis spectrum alongside of NBO calculation showed the five main electronic transition bands derived of n â n* of intraâligand alanine moiety of dipeptide structure.