P.M.V.B. Barone

Identifying carcinogenic activity of methylated polycyclic aromatic hydrocarbons (PAHs)

Abstract Polycyclic aromatic hydrocarbons (PAHs) are a class of planar molecules that can induce chemical carcinogenesis. Their carcinogenic power vary in a large range, from the very strong carcinogens to the inactive ones. Recently a new methodology was proposed (using the topological simple Huckel theory) to group and identify PAHs carcinogenic activity in terms of very simple rules based on the concept of electronic local density of states over specific molecular regions. In the present work we have extended this study to include methylated compounds. Our results show that the previous methodology can also be simplified and successfully used to predict the carcinogenic activity of methylated PAHs.

Electronic indices from semi-empirical calculations to identify carcinogenic activity of polycyclic aromatic hydrocarbons

Abstract Recently we have shown that it is possible to group and identify the carcinogenic activity of the polycyclic aromatic hydrocarbons (PAHs) using very simple rules derived from simple Huckel calculations. In this work we have carried out similar calculations using semi-empirical methods in order to investigate whether the derived rules are method dependent. We present PM3 (Parametric Method 3) and ZINDO-CI (Zerner Intermediate Neglect of Differential Overlap-Configuration Interaction) study on the electronic structure of PAHs. Very similar rules, based on the concept of electronic local density of states over specific molecular regions, are derived from PM3 calculations showing that they are essentially method independent. The analysis of the ZINDO-CI results for the intensity of the threshold transitions (first optical transitions) and the composition of the CI contributions also show a differentiated behavior for the strong carcinogenic molecules and the inactive ones.

A semi–empirical study on the electronic structure of ellipticines

Abstract Ellipticine and some of its derivatives are organic molecules with intense antitumor activity. In this work we report a semi–empirical study on the electronic structure of ellipticine and some derivatives. Geometrical and spectroscopic aspects were investigated through the use of the well–known PM3 (Parametric Method 3) and ZINDO (Zerner’s Intermediate Neglect of Differential Overlap) methods. Comparing PM3 and previously reported AM1 (Austin Method One) results, we found out that overall PM3 results are better. The ZINDO simulated absorption spectra compare well to the available experimental data. We have observed a very simple correlation between the dipole moment value (DM) and the antitumor activity. These results suggest a way to improve and design new antitumor ellipticine derivatives, as well as, to select promising molecules from untested groups.

Identifying carcinogenic activity of methylated and non-methylated polycyclic aromatic hydrocarbons (PAHs) through electronic and topological indices

Polycyclic aromatic hydrocarbons (PAHs) are a class of planar molecules, abundant in urban environment, which can induce chemical carcinogenesis. Their carcinogenic power varies in a large range, from very strong carcinogens to inactive ones. In a previous study, we proposed a methodology to identify the PAHs carcinogenic activity exploring electronic and topological indices. In the present work, we show that it is possible to simplify that methodology and expand its applicability to include methylated PAHs compounds. Using very simple rules, we can predict their carcinogenic activity with high accuracy (» 89%).

Theoretical characterization of oligocubanes

Cubanes are interesting molecules as structural units for a new class of materials, the polycubanes. It is believed that these materials can be used in the production of high-energy fuels as well as present remarkable properties. We report in this work a theoretical investigation on the electronic structure of oligocubanes using semiempirical and ab initio methods. Our geometrical data are in good agreement with the available experimental data. The possibility of using cubane derivatives to synthetize a new class of conducting polymer with small gap is also adressed.

A dual-mode photoswitching investigation

Abstract There is a great interest in the molecular switching processes in part due to the possibility of optical information storage at molecular level. In this work we report a theoretical study on the electronic structure of a dual-mode optical molecular switching system based on thioxantene derivatives helically shaped molecules. There are experimental evidences that these systems present ligth reversible modulation of chirality (cis to trans isomerization). The simulated electronic spectra are in good agreement with the experimental data and we have found a possible explanation on how the protonation interferes with switching mechanism.