Thiol-ene coupling reaction achievement and monitoring by "" UV irradiation NMR spectroscopy.

In this study, the possibilities of a new "" LED UV illumination NMR spectroscopic technique for performing an initiator-free thiol-ene "click" coupling reaction of an allyl-functionalized poly(allyl glycidyl ether) (PAGE) prepolymer with a number of mono- and di-oligo polyethylene glycol (PEG) thiols is demonstrated. The state-of-the-art setup constructed with LEDs as UV light sources that illuminate through optical fibers directly into an NMR testing tube at a fixed wavelength of 365 nm is appropriate for various polymeric materials and biologically active substances. The selected experimental protocol uses a series of periods of irradiation and dark periods, thus providing opportunities to conduct an effective thiol-ene "click" reaction and simultaneously study the kinetics of the photochemical reaction with the exposure time, as well as macromolecular association directly in a solution applying the whole types of NMR methods: from conventional H or C NMR to diffusion NMR spectroscopy (DOSY).

Comparative metabolism of N-tert-butyl-N-[1-(1-oxy-pyridin-4-yl)-ethyl]- and N-tert-butyl-N-(1-phenyl-ethyl)-nitroxide by the cytochrome P450 monooxygenase system.

The use of spin-trapping agents for a direct ESR detection of *OH in biological systems is limited by the low stability of the hydroxyl radical-derived nitroxides. Among the various probes used for trapping of *OH, DMSO has proven to be highly efficient. The reaction between *OH and DMSO yields methyl radical (CH(3)*), which can react with N-tert-butyl-alpha-phenylnitrone (PBN) and alpha-(4-pyridyl-1-oxide)-N-tert-butylnitrone (POBN) to form stable, ESR-detectable nitroxides.