Mikrochemie

Ohne Zusammenfassung     

Radiometric enzyme assays: development of methods for extremely sensitive determination of types 1, 2 and 3 iodothyronine deiodinase enzyme activities

We elaborated novel, reliable radiometric methods for extremely sensitive determination of enzyme activities of iodothyronine deiodinases (IDs) of types 1, 2 and 3 in microsomal fractions of different rat and human tissues, as well as in homogenates of cultured mammalian cells. These radiometric enzyme assays were based on the use of high-specific-radioactivity ¹²⁵I-labeled iodothyronines as substrates; TLC separation of radioactive products from the unconsumed substrates; film-less autoradiography of radiochromatograms using storage phosphor screens; and quantification of the separated compounds with a BAS-5000 laser scanner. This methodology enabled us to determine IDs enzyme activities as low as 10⁻¹⁸ katals. The applicability of our sophisticated methods was demonstrated by following the alterations of IDs activities induced in cultured astroglial cells by a series of purinergic agonists, retinoic acid, and their combination. In addition, in case of ATP as a representative of purinergic agonists, we determined time-course and dose–response curves to characterize in more details the induction of each type of deiodinase by purines.     

Addition polymerization of 1,1-dimesitylneopentylgermene: synthesis of a polygermene

A new polymer with an alternating germanium-carbon backbone has been synthesized from 1,1-dimesitylneopentylgermene via addition polymerization using an anionic initiator.     

Continuum mechanics and thermodynamics in the Hamilton and the Godunov-type formulations

Continuum mechanics with dislocations, with the Cattaneo-type heat conduction, with mass transfer, and with electromagnetic fields is put into the Hamiltonian form and into the form of the Godunov-type system of the first-order, symmetric hyperbolic partial differential equations (SHTC equations). The compatibility with thermodynamics of the time reversible part of the governing equations is mathematically expressed in the former formulation as degeneracy of the Hamiltonian structure and in the latter formulation as the existence of a companion conservation law. In both formulations the time irreversible part represents gradient dynamics. The Godunov-type formulation brings the mathematical rigor (the local well posedness of the Cauchy initial value problem) and the possibility to discretize while keeping the physical content of the governing equations (the Godunov finite volume discretization).     

Copper cation interactions with biologically essential types of ligands: a computational DFT study

This work presents a systematic theoretical study on Cu(I) and Cu(II) cations in variable hydrogen sulfide-aqua-ammine ligand fields. These ligands model the biologically most common environment for Cu ions. Molecular structures of the complexes were optimized at the density functional theory (DFT) level. Subsequent thorough energy analyses revealed the following trends: (i) The ammine complexes are the most stable, followed by those containing the aqua and hydrogen sulfide ligands, which are characterized by similar stabilization energies. (ii) The most preferred Cu(I) coordination number is 2 in ammine or aqua ligand fields. A qualitatively different binding picture was obtained for complexes with H(2)S ligands where the 4-coordination is favored. (iii) The 4- and 5-coordinated structures belong to the most stable complexes for Cu(II), regardless of the ligand types. Vertical and adiabatic ionization potentials of Cu(I) complexes were calculated. Charge distribution (using the natural population analysis (NPA) method) and molecular orbital analyses were performed to elucidate the nature of bonding in the examined systems. The results provide in-depth insight into the Cu-binding properties and can be, among others, used for the calibration of bioinorganic force fields.