64525-01-5Relevant articles and documents
Human erythrocyte membrane permeability and nitroxyl spin-label reduction
Eriksson,Tozer,Sosnovsky,Lukszo,Brasch
, p. 334 - 337 (1986)
Nitroxyl spin labels are paramagnetic compounds that have demonstrated utility as contrast enhancing agents in proton magnetic resonance imaging. The time-course of contrast enhancement depends on distribution and elimination of these agents. Reduction, resulting in formation of the diamagnetic hydroxylamine, is the major metabolic pathway observed in vivo. This bioreduction has implications for the design of contrast agents and for understanding their imaging behavior. Bioreduction has been shown to occur, at least in part, intracellularly. As such, cell membrane permeability to nitroxyl spin labels may influence their bioreduction. In this study, this influence was examined using eight nitroxyl derivatives and the human erythrocyte suspension as a model biomembrane system. Ionizable weak acids and bases were found to equilibrate rapidly across the erythrocyte membrane with half-times of equilibration ranging from 10 s to 1.6 min. These derivatives had low octanol:buffer distribution coefficients and were extensively ionized at the pH of the system (7.0). A strong acid, a phosphatase ester, and a quaternary amine derivative were excluded by the cell membrane. Reduction of nitroxyl spin labels by the erythrocyte was shown to occur intracellularly. Except for the impermeable probes, the reduction rate was slow in comparison with the membrane penetration rate. The structural dependence of reduction rate was unrelated to penetration rate but correlated well with that observed in other reducing systems, namely, ascorbic acid solution and rat tissue homogenates.
Inversion-recovery of nitroxide spin labels in solution and microheterogeneous environments
Koptyug,Bossmann,Turro
, p. 1435 - 1445 (1996)
Two modifications of a conventional inversion-recovery experiment which exclude the effect of spectral diffusion on the measured spin-lattice relaxation times of rapidly tumbling nitroxide spin labels are described. In the first approach an almost uniform inversion is achieved by means of specially designed pulse trains with excitation patterns which match the three-line nitroxide ESR spectrum. In the second approach we essentially combine an inversion-recovery for the M1 = 0 line with an analog of a pulsed ELDOR technique for M1 = ±1 lines in a single experiment. This allows us to reconstruct the recovery of the total magnetization of ensemble of radicals which is not affected by spectral diffusion. The spin-lattice relaxation times of several nitroxide spin labels in different homogeneous and microheterogeneous environments are measured and compared. The temperature dependence of T1 times is compared for two solvents, methylcyclohexane and carbon disulfide, which differ in nuclear spin concentration by almost a factor of 1000. The reported experimental evidence suggests that interactions with the nuclear spins of a solvent do not significantly contribute to the spin-lattice relaxation of nitroxide spin labels.
A π-Conjugation Extended Viologen as a Two-Electron Storage Anolyte for Total Organic Aqueous Redox Flow Batteries
Luo, Jian,Hu, Bo,Debruler, Camden,Liu, Tianbiao Leo
, p. 231 - 235 (2018)
Extending the conjugation of viologen by a planar thiazolo[5,4-d]thiazole (TTz) framework and functionalizing the pyridinium with hydrophilic ammonium groups yielded a highly water-soluble π-conjugation extended viologen, 4,4′-(thiazolo[5,4-d]thiazole-2,5-diyl)bis(1-(3-(trimethylammonio)propyl)pyridin-1-ium) tetrachloride, [(NPr)2TTz]Cl4, as a novel two-electron storage anolyte for aqueous organic redox flow battery (AORFB) applications. Its physical and electrochemical properties were systematically investigated. Paired with 4-trimethylammonium-TEMPO (NMe-TEMPO) as catholyte, [(NPr)2TTz]Cl4 enables a 1.44 V AORFB with a theoretical energy density of 53.7 Wh L?1. A demonstrated [(NPr)2TTz]Cl4/NMe-TEMPO AORFB delivered an energy efficiency of 70 % and 99.97 % capacity retention per cycle.
Synthesis of 4-trimethylammonio-2,2,6,6-tetramethylpiperidine-1-yloxyl with various anions for investigation of ionic liquids
Strehmel, Veronika,Rexhausen, Hans,Strauch, Peter
, p. 3264 - 3267 (2008/09/20)
A new synthetic way is described to prepare 4-trimethylammonio-2,2,6,6-tetramethylpiperidine-1-yloxyl bearing tetrafluoroborate, hexafluorophosphate or bis(trifluoromethylsulfonylimide) by an anion metathesis of 4-trimethylammonio-2,2,6,6-tetramethylpiperidine-1-yloxyl iodide using the corresponding silver salts. 4-Trimethylammonio-2,2,6,6-tetramethylpiperidine-1-yloxyl iodide is obtained by the methylation of 4-amino-2,2,6,6-tetramethylpiperidine-1-yloxyl with methyliodide. The new spin probe 4-trimethylammonio-2,2,6,6-tetramethylpiperidine-1-yloxyl bistrifluoromethylsulfonylimide and the spin probes containing tetrafluoroborate or hexafluorophosphate may be useful for an effective investigation of ionic liquids with similar anions.
