Chemically Induced Dynamic Electron Polarization Generated through the Interaction between Singlet Molecular Oxygen and Nitroxide Radicals

Abstract

An absorptive chemically induced dynamic electron polarization (CIDEP) was generated by the quenching of singlet oxygen by nitroxide radicals (TEMPO derivatives). The spin polarization decay time of the nitroxide (measured by time-resolved EPR) correlates with the lifetime of singlet oxygen (measured by singlet oxygen phosphorescence spectroscopy). In addition, a deuterium isotope effect on the spin polarization decay time was observed, a signature of singlet oxygen involvement. With use of isotope labeled nitroxides ( 15 N, 14 N), the relative spin polarization efficiencies of TEMPO, 4-oxo-TEMPO, and 4-hydroxy-TEMPO by singlet oxygen were determined. The relative spin polarization efficiencies (per quenching event) decrease in the order 4-hydroxy-TEMPO > TEMPO > 4-oxo-TEMPO, whereas an opposite trend was observed for the total quenching rate constants of singlet oxygen by the nitroxides where the order is 4-hydroxy-TEMPO < TEMPO < 4-oxo-TEMPO.

Photoinduced Oxidation of Sterically Hindered Amines in Acetonitrile Solutions and Titania Suspensions (An EPR Study)

“…3). However, with the highest water ratio (40%; vol), a limitation in the increase in >NO • concentration was observed during irradiation, which can be caused by: (1) decomposition of the superoxide radical anion in aqueous media (34,35), (2) differences in the lifetime of singlet oxygen in water (4.6 μs) and in acetonitrile (71 μs; 36) and (3) the consecutive reactions of photogenerated nitroxides with ROS producing diamagnetic compounds (12,37–39).…”

“…Increase in the TiO 2 concentration causes a substantial increase in the nitroxide radical concentration formed upon irradiation, up to a titania loading of 0.4 g L −1 , at which point a limitation in the initial rate of nitroxide formation is observed and with even higher concentrations of TiO 2 the concentration of paramagnetic nitroxide species decreases upon prolonged irradiation (Fig. 8), most probably due to the termination reactions with ROS generated in TiO 2 system (37–39,63).…”

Nitroxide free radicals protect macular carotenoids against chemical destruction (bleaching) during lipid peroxidation

“…Spin labels quench singlet oxygen, although their quenching ability as compared with carotenoids is significantly lower. In the hydrophobic solvents, the quenching rate constant for TEMPO and TEMPO derivatives is ~10 5 –10 6 M −1 s −1 [62–64], while for Zea it is 1.2 ×10 10 M −1 s −1 [16]. In the aqueous phase, the water-soluble CTPO and the water-located portion of TEMPO can also quench water-located singlet oxygen and further may quench the exited state of rose bengal.…”

Is it possible to design isotopic mass-dependent ms-patch-clamp and isotopic mass-independent esr-patch-clamp?

“…Buchachenko (Buchachenko, 2013). The theory of the mass-independent isotope effect (also known as «magnetic isotope effect») proposed and developed by A. Buchachenko has been applied to a number of biochemical processes and objects, including the synthesis of semantids (Buchachenko, 2013a; Buchachenko, 2013b), enzymatic ATP synthesis (Buchachenko, 2008; Buchachenko, 2008a; Buchachenko, 2010; Buchachenko, 2012) and intramitochondrial phosphorylation (Buchachenko, 2004;Buchachenko, 2005;Buchachenko, 2005a), ATP synthase efficiency as a molecular machine and magnetic mechanochemistry of the phosphorylating agents (Buchachenko, 2005b;Buchachenko, 2006;Buchachenko, 2008b;Buchachenko, 2008c). It has been noted that the magnetic magnesium isotope delivered by the membranotropic cationexchanging fullerene-based nanoparticles into the myocardial cells is capable of the hypoxia-caused metabolic acidosis treatment by means of the reactivation of ATP synthesis, and thus, provides normalization of both intracellular proton concentration and the heart muscle cell membrane potential (Amirshahi, 2008;Rezayat, 2009;Shetab Bousheri, 2010).…”