Head: Dr. Branka Kovač

Project is based on the biologically active molecules investigation by photoelectron spectroscopy (PES), electronic spectrophotometry (UV-Vis) and mass (EI, LDI and MALDI FT ICR) spectrometry. EPR measurements and quantum-chemical calculations will also be used. These studies can provide answers concerning composition, properties and reactions of investigated molecules. Activity and molecular reactivity of biologically important molecules depend on their composition, shape and their electronic structure. Structure investigation relies on understanding the way biologically active molecules act since it may indicate the possible mechanism of action and suggest specific changes to be made in particular positions within the molecule. Possibilities PES provides us with are irreplaceable, especially in conjunction with high level quantum-chemical calculations. Gas phase homogeneous ligand-metal interactions (ligands being policyclic aromatic hidrocarbons and their heteroanalogous, porphyrines, crown ethers, stable radicals, flavonoid compounds etc.) will be investigated by FT ICR MS. Since one of its characteristics is to keep ions in the instrument up to few seconds, it is possible to monitor their decomposition, synthesize new compounds and determine thermodynamic observables for these ions and newly formed products. Molecular properties are being studied in the gas phase under high vacuum, and can thus be considered as their intrinsic properties. Since interactions of ligands with metal ions take place under electron transfer these investigations may give intrinsic reactivity of compounds that are important natural antioxidants. Namely, antioxidant activity is difficult to measure quantitatively and there is no satisfactory method to be used so far. Thus we are going to study that activity in the solution too, with flavonoid class of compounds in reactions with metal ions, stable radicals and reactive oxygen species (ROS). Experimental results will be checked by quantum-chemical calculations and modelling. Electronic structure results will be confirmed by reactivity studies of substituted benzenes which are frequent constitutive parts of biological molecules. A part of investigation will deal with polysubstituted halobenzenes. Results are expected to give answers to the questions about intrinsic reactivity of reactants and help to determine mechanisms of action of biomolecules and parameters (factors) important for biological activity.