The hyaluronate molecule is a negatively charged polysaccharide that performs a plethora of physiological functions in many cell tissues depending on its conformation. In the present paper, molecular modeling at three levels of theory and two basis sets was used to gain a deeper insight in the complex molecular structure of calcium(II) and copper(II) hyaluronate. Simulation results were compared with the experimental data (EXAFS or X-ray). It was found that B3LYP does not properly reproduce the experimental data while the HF and M06 methods do. Simulation data confirm that the N-acetyl group of the N-acetylglucosamine residue does not participate in the coordination bonding to the calcium(II) or copper(II) ion, as evident from the experimental data.
COBISS.SI-ID: 36212485
The purpose of this work was to determine the influence of mechanical and electrical treatment on the electrical conductivity of aqueous solutions. Solutions were treated mechanically by iteration of two steps: 1:100 dilution and vigorous shaking. These two processes were repeated until extremely dilute solutions were obtained. For electrical treatment the solutions were exposed to strong electrical impulses. Effects of mechanical (as well as electrical) treatment could not be demonstrated using electrical conductivity measurements. However, significantly higher conductivity than those of the freshly prepared chemically analogous solutions was found in all aged solutions except for those samples stored frozen. The results surprisingly resemble a previously observed weak gel-like behavior in water stored in closed flasks. We suggest that ions and contact with hydrophilic glass surfaces could be the determinative conditions for the occurrence of this phenomenon.
COBISS.SI-ID: 35901957
We studied uncatalyzed oxidation of sulfides into sulfones by using 30% aqueous solution of hydrogen peroxide at 75°C under solvent-free reaction conditions. It was established that the reaction in several cases took place with high level of atom economy because 10% excess of H2O2 was used only. Structurally different phenyl alkyl-, phenyl benzyl-, benzyl alkyl-, dialkyl-, heteroaryl alkyl- and cyclic sulfides were converted into sulfones under the mentioned conditions. The unsaturated sulfides, containing double and triple bonds also reacted well. The most of the sulfides were nonpolar and hydrophobic, thus unable to mix with the solution of H2O2 and in spite of the heterogeneous reaction conditions, the reactions took place well. The transformation is suitable for the synthesis of sulfones on larger scale (≈ g), while the reaction times were longer on larger scale. A substantial number of sulfides exist in the solid aggregate state and could be isolated by filtration and crystallized. This is an important advantage of this method, because extraction, chromatography and the use of organic solvents could be greatly avoided.
COBISS.SI-ID: 36306437
We studied a chemistry of polyvalent iodine(I) compounds and developed new method for their preparation using molecular iodine, hydrogene peroxide as the oxidant and HCl as the activator of the process. These compounds were isolated as tetraelkyl or pyrindium salts, which were further used as iodinating reagent for organic compounds. This method represents an original new approach where iodo(I) specia play a role of the source of the iodine atoms. The presence of hydrogen chloride is essential, but only in presence catalytic amounts, what makes this method very attractive.
COBISS.SI-ID: 26066983
Phytotoxicity and composition of two landfill leachates were studied. Phytotoxicity testing and physico-chemical parameters showed that the leachate generated in the active part of the landfill was significantly polluted and more toxic to plants than the leachate generated in the closed part of the landfill, which did not cause any significant adverse effects on root growth of plants tested in soil. However, the highest toxic effect of both leachates has been observed in the first days of plant germination. Phytotoxic pollutants have probably been degraded in the closed part of the landfill and leachates from such landfills are not significantly toxic to plants. Therefore phytoremediation appeared to be an appropriate restoration and treatment method.
COBISS.SI-ID: 35850757