R E S E A R C H

Ab initio description of radicals in solution and of their reactivity, with particular interest for radicals of biological relevance. My research aims to include in our density functional (and eventually time-dependent density functional) schemes new exchange-correlation approximations free of self-interaction errors. This modification is needed to provide the correct description of the spin and oxidation state of open shell systems, reducing at the same time the spin contamination error. Applications awaiting this improvement include the proper description of radical ions in the gas phase and in solution. Recent achievements include the computation of electronic energy levels of aqueous oxidation products of water focusing on the question how these levels are aligned with the energy levels in solid electrodes (metals and semiconductors)[5]. Radical species constanly occur as intermediates in both natural redox reaction and in the devices for energy production, such as fuel and solar cells. Our developments provide an affordable solution for extended systems where multi-configurational approaches are currently not feasible.

[5]Adriaanse CJ, Sulpizi M, Vandevondele J and Sprik,to appear in JACS, (2009).

QM/MM techniques: enzymatic catalysis and optical properties: in the group of Prof. Rothlisberger I contributed to the development, implementation and testing of QM/MM methods within the CPMD code (http://www.cpmd.org). Key applications include studies of enzymatic reactions (caspases) and of the optical properties of chromophores in solution. In particular in the case of caspases we addressed the key steps of the enzymatic reaction for a representative member of this family, caspase-3. These calculations show that the attack of the hydrolytic water molecule implies an activation free energyin good agreement with experimental data and leads to a previously unrecognized gem-diol intermediate that can readily dissociate. Our findings[6] assist in elucidating the striking difference in catalytic activity between caspase and other structurally well-characterized cysteine proteases (papains and cathepsins). The optical properties of molecules in complex environments were investigated within hybrid time-dependent density functional theory / molecular mechanics (TDDFT/MM) simulation studies. We appled this TDDFT/MM technique to the study of the properties of the ground state and of the first excited singlet state of different systems including acetone in water and aminocoumarins in water and acetonitrile. Our approach yields quantitative information on the solvent-induced shifts, both batho- and hypsochromic, of the electronic absorption spectra, and on the effect of a protic and an aprotic solvent on the spectral shift[7].

[6]Sulpizi M, Laio A, VandeVondele J, Cattaneo A, Rothlisberger U and Carloni P. Proteins: Struc, Func, and Gen, 52 212 (2003).
[7] Sulpizi M, Carloni P, Hutter J, Rothlisberger U, Phys. Chem. Chem. Phys. 5 4798 (2003);
Sulpizi M, Röhrig UF, Hutter J, and Rothlisberger U, Int. Journal of Quantum Chemistry 101 671 (2005).

To contact me:
sulpizi@uni-mainz.de

Tel: +49 6131 3923641
Fax: +49 6131 3920496

Dr Marialore Sulpizi
Johannes Gutenberg University Mainz,
Staudinger Weg 7
55099 Mainz
Germany.