Interaction of angelicin with DNA bases (III) DFT and Ab initio second-order Moeller-Plesset study

Abstract

Angelicin geometry was optimized at MP2/6-31+G(d,p) level and compared with X-ray experimental data. The highest π-electron density was found to be localized on C1-C2 and on C13-C14 as confirmed by the calculated bond length and bond order values. Spectrophptometric properties of angelicin were measured and compared with the computed within the TD-DFT. Quantum chemical methods were used to study the interaction of angelicin, as a nonlinear furocoumarin, with DNA bases and base pairs. The interactions with DNA bases and base pairs were studied to shade more light on the nature of the intercalation binding forces between angelicin and DNA. Comparing computed electronic properties of angelicin with that of linear psoralens show that the former is a weaker intercalator. The geometry of complexes of angelicin with adenine, thymine, adenine-thymine base pair, cytocine, guanine as well as cytocine-guanine base pair have been optimized in two main orientations, planar and stacked, at the levels of B3LYP/cc-pVDZ, MP2/6-31G(d,p) and MP2/cc-pVDZ. Effect of vertical distance and rotational angle between the stacked molecules on the interaction energy were investigated by the aforementioned methods in gas phase and water media. It was found that ab initio methods which account for the electron correlation effects are the minimum level for studying the noncovalent interactions.© 2009 Wiley Periodicals, Inc.