The effect of micellization on the EPR spectra and reactivity of 2,2,4,4-tetramethylpiperidinoxyl (TEMPO) radicals

Abstract

A series of 4-alkanoyloxy-2,2,6,6-tetramethylpiperidinoxyl radicals was prepared, and their reactivity in water vis-à-vis antioxidant Trolox was compared. Spectral (electron paramagnetic resonance) and dynamic-light-scattering measurements suggested the formation of micelles for the more hydrophobic members of the series. The observed increase in reactivity for the micelle-forming radicals reflected the increased local concentration of the radical fragment on the micellar interface. Copyright © 2016 John Wiley & Sons, Ltd.

Degradation of tetracycline by visible light using Ca2Nb2O7 composite oxides with perovskite and pyrochlore sub-crystalline phases

“…During the reaction, the h + carriers generated on the catalyst surface combine with the single electrons of TEMPO, resulting in a decrease in the TEMPO signal, indicating the formation of h + in the reaction. 25,26 As indicated in Fig. 6(d), the ESR signal intensities of the two catalysts are similar in the dark.…”

Highly Sensitive “Off/On” EPR Probes to Monitor Enzymatic Activity

“…This frequency‐encoding modality allows an unambiguous detection of the enzymatic product, but the attainable sensitivity level appears until now limited [5,6] . We deemed of interest to investigate alternative routes taking advantage of the fact that nitroxide radicals are “quenched” when they are immobilized on nanostructures like proteins, [7] vesicles, micelles or liposomes [8,9] as a consequence of dipole‐dipole interactions and increasing spin exchange between the closely packed radical molecules [10] . In alternative, Lu Yu and coworkers [11] recently observed a significant quenching of the EPR signal generated by the dipolar interaction with a paramagnetic center (Gd‐complex) linked through a short protease‐specific peptide to the nitroxide radical.…”