Andrzej Les

Modelling of Octahedral Manganese II Complexes with Inorganic Ligands: A Problem with Spin-States

Quantum mechanical ab initio UHF, MP2, MC-SCF and DFT calculations with moderate Gaussian basis sets were performed for MnX6, X = H2O, F-, CN-, manganese octahedral complexes. The correct spin-state of the complexes was obtained only when the counter ions neutralizing the entire complexes were used in the modelling at the B3LYP level of theory.

Theoretical and matrix-isolation experimental studies on 2-thiocytosine and 5-fluoro-2-thiocytosine

2-Thiocytosine (s2Cyt) and 5-fluoro-2-thiocytosine (f5s2Cyt) were studied by means of IR spectroscopy under different environmental conditions: isolated in low-temperature inert gas matrices, associated in thin amorphous and polycrystalline films. The compounds isolated in matrices were only very slightly influenced by the environment. From the analysis of the IR spectra of both compounds it appears that they exist in inert gas matrices only in the amino-thiol tautomeric form. Strong environmental effects were observed for s2Cyt and f5s2Cyt deposited in the form of thin polycrystalline films. Contrary to matrices, in polycrystalline films the amino-thione form dominates for both s2Cyt and f5s2Cyt. The experimental findings are in agreement with the ab initio quantum mechanical calculations of the relative total energies of the tautomeric forms. Those energies were calculated using the Self Consistent Field method corrected for electron correlation effects with the use of the second-order many-body perturbation theory (SCF+MBPT(2)). The theoretical calculations show that the amino-thiol tautomeric form is more stable than the amino-thione form by 38 kJ mol-1 and 48 kJ mol-1 for s2Cyt and f5s2Cyt, respectively. Both molecules, s2Cyt and f5s2Cyt, may also appear in the uracil-like imino-thione tautomeric form, which is predicted to be only 8 kJ mol-1 less stable than the amino-thione form. A new method of the preparation of f5s2Cyt is reported.

Altering the Orientation of Proteins on Self-Assembled Monolayers: A Computational Study

A combined computational docking-molecular dynamics study has been performed on a system consisting of cytochrome c protein and alkanethiol self-assembled monolayers of various geometries. The results suggest that the orientation of the protein on the surface may be controlled or altered by means of designing specific structural motifs on the surface. The proposed computational approach may be used as a fast and reliable tool to complement other theoretical and experimental techniques of exploring other protein-surface interfaces.

Theoretical study of simple electron transfer reactions involving oxo radicals and anions

Abstract The heat of electron transfer reactions involving oxo radicals and anions is calculated using the first-order correlation orbitals and the coupled cluster method. Despite systematic errors which remain in the theoretical electron affinities versus the experimental affinities, the agreement in the electron transfer energy is much more plausible.