Theoretical investigations on some biological systems

Abstract

In this thesis molecular properties of different biological systems are studied by means of Quantum Mechanical methods. After a brief introduction, the basic theory of the methods here used is presented in Chapter 1. In Chapter 2 the heats of formation and the ionization potentials of some carcinogenic compounds such as Polycyclic Aromatic Hydrocarbons are studied and compared with experimental data. The methods used are the semiempirical methods with the AM1 and PM3 Hamiltonians. The results show that the experimental heats of formation are better reproduced by PM3, while as far as the ionization potentials are concerned AM1 is slightly better than PM3. In Chapter 3, the Lipid Peroxidation mechanism has been studied at the molecular level. The energetic details of the pathway proposed by Porter have been studied using the semiempirical AM1 and PM3 Hamiltonians. Six model compounds, which retain the same functional characteristics as the physiological fatty acid, have been used. The results are in good agreement with the experimental observations. Characteristics and metabolism of the anticancer drug NMF (N-Methylformide) have been studied in detail in Chapter 4. Accurate ab initio calculations have been carried out and the effect of the solvent has been taken into account. The results represent a good example of the high quality of information that the application of ab initio methods can give when properties of molecules and energetic details of pathways are examined.