In vitro effects of ozone on human erythrocyte membranes: an EPR study.

The effects of ozone at different concentrations (10, 30, 45 g/m3) on fluidity and thermotropic properties of erythrocyte membranes were investigated by EPR using two spin probes: 5-doxylstearic acid (5-DSA) and 16-doxylstearic acid (16-DSA). The effect of ozone on the erythrocyte membrane fluidity was a dose-dependent process. The ozone at concentration of 10 g/m3 caused rigidization of the membrane while at concentration of 45 g/m3 increased fluidity both on the surface and in the deeper hydrocarbon region of the membrane. Temperature transitions close to the polar heads region (monitored by 5-DSA) were not sensitive to an increase in ozone concentration. In the case of 16-DSA, low temperature thermotropic transition (around 20 degrees C) gradually decreased with the increase of ozone concentration. High temperature transition (around 40 degrees C) significantly differed at the ozone concentration of 10 g/m3 and 45 g/m3, being higher and lower, respectively, as compared to untreated cells. For the ozone concentration of 45 g/m3 the disappearance of the low temperature break and the appearance of two breaks at 37 degrees C and 16 degrees C were observed.</jats:p

Evidence for a charge transfer from spilt-over hydrogen to platinum by means of ESR spectroscopy

An electron transfer from spilt-over hydrogen (H*) to platinum on a Pt/γ-Al2O3 catalyst has been investigated by ESR spectroscopy. Activated hydrogen is formed on Pt clusters and the resulting atomic H* species migrate onto the alumina surface where they can interact with single Pt atoms. The chemisorption of H* at 77 K leads to the appearance of ESR signals which are related to the formation of Ptn− species. This charge transfer is correlated to the formation of H+ ions from initially present radical hydrogen spillover species

Influence of Cation Exchange on the ²⁷Al-NMR Spectra of Zeolites

The influence of cation exchange on the ²⁷Al-NMR spectra of NaA-zeolites has been studied by ²⁷Al-MAS- and MQ-MAS-Solid State-NMR. From the ²⁷Al-spectra a characterization of the different Al sites in the A zeolites according to their chemical environment and the structural changes on the aluminosilicate network caused by the cation exchange are obtained. It is found that the exchange with cations with smaller ion-radius cause stronger distortions of the ²⁷Al-NMR-spectra than exchange with larger cations like Ba²⁺. Employing MQ-MAS spectroscopy these distortions are revealed as second order quadrupolar effects for the smaller cations and as a combination of chemical shift and second order quadrupolar interaction for the Ba cation. These changes of the quadrupolar coupling are interpreted numerically via calculations of the lowering of the symmetry of the EFG tensor. Finally it is found that the exchange with divalent cations leads to distortions of the zeolitic framework and the formation of an extra-framework aluminum. To the best of our knowledge this is for the first time that evidence for the production of extra frame work aluminum by pure cation exchange without any thermal treatment has been found in type A zeolites