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EPR study of the effect, induced by zidovudine (AZT), on the membrane lipid dynamics in leukemic cell
No full textZidovudine (AZT) was the first drug approved by the FDA for treatment of HIV infections. To investigate the AZT effects on the physical properties of K562 cell membranes, experiments were performed by measuring an order parameter value in these cells, previously labelled with 16-DSA (16-doxyl-stearic acid) or 5-DSA (5-doxyl-stearic acid). The EPR spectra of the labelled fatty acid were used to detect the alteration in their freedom of motion and to provide indications of membrane fluidity. Two different parameters were calculated from EPR spectra for the 16-DSA and 5-DSA. Preliminary data indicate that, for both the probes used, these parameters were not significantly different in the control cells with respect to the AZT-treated ones. Control measurements, performed to test the sensitivity of the technique using the DMSO agent, showed a significant increase in the K562 membrane fluidity
An EPR study of lipid vesicles as paramagnetic agent vectors
No full textParamagnetic nitroxides have been proposed as probes in electron paramagnetic resonance (EPR) imaging and in clinical diagnosis. However, nitroxides are rapidly reduced in vivo to hydroxylamines, diamagnetic EPR-inactive species. Reduction occurs in blood via soluble agents such as ascorbic acid, as well as in the cells via enzymatic and non-enzymatic endocellular systems. To prevent the reduction, a water soluble nitroxide, i.e., potassium peroxylamine disulfonate, is entrapped in reverse phase evaporation vesicles. The loaded liposomes have a high entrapment capacity, and vesicles with the encapsulated agent are stable for days, even at room temperature. The vesicles in vitro can almost completely prevent the reduction of the entrapped nitroxide by ascorbic acid. In blood of a rat, enriched with a homogenate of rat liver proteins, the vesicles are able to greatly prolong the life time of the nitroxide. In particular, the encapsulated nitroxide has a half-life of more than one hour, compared to two minutes for free nitroxide under the same conditions. Due to these protective effects, the lipid vesicles might be useful as a delivery system for paramagnetic agents
Palladium-catalysed cyclization of 2-alkynylanilines to 2-substituted indoles under an acidic two-phase system
No full textThe cyclization of 2-alkynylanilines in the presence of PdCl2 and nBu4NCl under an acidic CH2Cl2-HCI two-phase system affords 2-substituted indoles in good to high yield, at room temperature. The reaction is particularly suited to the one-flask preparation of 2-substituted indoles from 2-ethynylaniline
2-Substituted-3-acylindoles through the Palladium-Catalysed Carbonylative Cyclization of 2-Alkynyltrifluoroacetanilides with Aryl Halides and Vinyl Triflates
No full textThe palladium-catalysed reaction of readily accessible 2-alkynyltrifluoroacetanilides with aryl hanides and vinyl triflates under a carbon monoxide atmosphere (1 or 7 atm) the presence of potassium carbonate produce s 2-substituted-3-acyl indoles in fair to good yield. The acidity of the nitrogen-hydrogen bond proved to be of primary importance for the success of the reaction. The methodology has been applied to the synthesis of pravadoline, a drug that shows analgesic activity against postoperative pain in man
Antibacterial effect of bovine lactoferrin and its derived peptide mixtures by enzymatic proteolysis
No full textStatic magnetic field effect on the Fremy’s salt–ascorbic acid chemical reaction studied by continuous-wave electrom paramagnetic resonance
No full textStatic magnetic field effect in the framework of the radial pair mechanism (RPM) theory was studied on the biologically significant chemical reaction between ascorbic acid and Fremy’s salt. The data indicate that the reaction rate depends on the applied magnetic field strength. The time scale of the studied reaction and the improved continuous-wave electron paramagnetic resonance system allowed for the first time the direct comparison of the amplitude differences between exposed and control samples in the strictly same boundary conditions. Until now the RPM was studied in a different time scale, focusing only on faster reactions by time-resolved techniques or by spectrophotometer measurement. The magnetic field effects presently measured can not be extended tout court to living systems; however the understanding of magnetic field sensitivity in basic chemical reaction in vitro could help clarifying the underlying basic step of interaction between magnetic fields and biological systems
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