Turcheniuk K.V.,Institute of Bioorganic Chemistry and Petrochemistry of NAS of Ukraine |
Shevchenko I.V.,Institute of Bioorganic Chemistry and Petrochemistry of NAS of Ukraine
Journal of Fluorine Chemistry | Year: 2012
The negatively charged carbon atom of phosphorus ylides is capable of increasing the nucleophilicity of the triple CN bond. The nitrile group activated in this way can add two equivalents of hexafluoroacetone with the formation of trifluoromethyl substituted 4H-1,2,3-dioxazines. Due to delocalization of the ylidic negative charge one of the C-C bonds acquires a double bond character, the consequence of which is the existence of E/Z-isomerism in these compounds. © 2011 Elsevier B.V. All rights reserved.
PubMed | Institute for Food Biotechnology and Genomics of NAS of Ukraine and Institute of Bioorganic Chemistry and Petrochemistry of NAS of Ukraine
Type: Journal Article | Journal: Journal of liposome research | Year: 2016
Comparative properties of lecithin-based liposomes prepared from the mixed phospholipids of sunflower seeds, soybean and egg yolk were investigated by electron paramagnetic resonance (EPR) spectroscopy. For these investigations, stable nitroxide radicals, 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl 5,7-dimethyladamantane-1-carboxylate (DMAC-TEMPO), 5-doxylstearic acid (5-DSA) and 16-doxylstearic acid (16-DSA) were used as spin probes. Binding of the spin probes to the liposome membranes resulted in a substantial increase of the apparent rotational diffusion correlation times. The EPR spectra of the incorporated nitroxides underwent temperature-dependent changes. For every spin probe, values of apparent enthalpy and entropy of activation were calculated from the temperature dependence of rotational diffusion correlation times via Arrhenius equation. In case of DMAC-TEMPO, the data point to differences between the phospholipid bilayer of liposomes derived from sunflower and soy lecithin, and some similarity between the sunflower and egg yolk liposomes. Anisotropic hyperfine interaction constants of DMAC-TEMPO and 16-DSA included in the liposomes have been analyzed and attributed to different micropolarity of the surroundings of the spin probes. The kinetics of EPR signal decay of DMAC-TEMPO in the presence of 2,2-azobis(2-amidinopropane) suggest the better stability of the sunflower liposomes to lipid peroxidation as compared to the liposomes prepared from soy lecithin.