Near-surface structure of Nafion in deuterated water.

The swelling of a polymer ion-exchange membrane Nafion in water with various heavy isotope contents (D2O) was studied by photoluminescent UV spectroscopy. The photoluminescence arises because of the presence of sulfonic groups attached to the ends of the perfluorovinyl ether groups that form the tetrafluoroethylene (Teflon) backbone of Nafion. The width of the colloidal region, which is formed near the membrane surface as a result of the outgrowth of Nafion microfibers toward the bulk liquid, varies non-monotonically with D2O content, displaying a narrow maximum in the low concentration region. A significant insight into the unexpected isotopic effects revealed in swelling Nafion in deuterated water is provided. Mainly, the polymer swelling is very sensitive to small changes (on the order of several tens of parts per million) in the content of deuterium, which, for instance, can help in understanding the isotopic effects in living tissues.

Mechanical Transformation of Compounds Leading to Physical, Chemical, and Biological Changes in Pharmaceutical Substances.

This study demonstrates the link between the modification of the solid-phase pharmaceutical substances mechanical structure and their activity in waters with different molar ratio «deuterium-protium¼. Mechanochemical transformation of the powders of lactose monohydrate and sodium chloride as models of nutrients and components of dosage forms was investigated by the complex of physicochemical and biological methods. The solubility and kinetic activity of substances dispersed in various ways showed a positive correlation with the solvent isotope profile. Substances dissolved in heavy water were more active than solutes in natural water. Differential IR spectroscopy confirmed the modification of substituents in the sample of lactose monohydrate, demonstrating physicochemical changes during mechanical intervention. The biological activity of the compounds was determined by the method of Spirotox. The activation energy was determined by Arrhenius. Compared with the native compound, dispersed lactose monohydrate showed lower activation energy and, therefore, greater efficiency. In conclusion, proposed data confirm the statement that mechanical changes in compounds can lead to physicochemical changes that affect chemical and biological profiles.

[The modern approaches to the determination of the content of elemental impurities in the pharmaceutical substances with the use of inductively-coupled plasma mass-spectrometry].

The elemental impurities contained in the composition of the pharmaceutical dose forms are known to be capable of interacting with their active substances and excipients and of catalyzing their degradation; thereby, they alter stability of the drug products and exert toxic effects on the human tissues. The present publication was designed to report the results of the purity tests for ascorbic acid, valine, and galactose substances by inductively-coupled plasma mass-spectrometry (IBP-MS). This method is recommended for use by the US and EU pharmacopoeias and for the replacement of the traditional test for heavy metals with the use of PbS ethanol suspension.

Role of plasmids in the formation of E. coli polycellular forms.

The formation of polycellular forms by E. coli strain K-12 cells containing F-like plasmids pAP22-2 and pAP42 was studied by the method of small-angle laser scattering. The efficiency and patterns of the resultant cell associations depend on genetic characteristics of the studied plasmids.