Nitroxyls probes

A116. Utsumi, H. and K. Yamada In vivo electron spin resonance-computed tomography/nitroxyl probe technique for non-invasive analysis of oxidative injuries Arch. Biochem. Biophys. 416 (2003) 1-8. 

Sano et al reported the development and use of another new nitroxyl probe, carboxy-proxyl acetoxymethyl ester (CxP-AM) for brain imaging. Its advantage over previous probe molecules is that it is able to cross the blood-brain barrier, but once inside the brain it is hydrolysed and retained there. In vivo L-band EPRI measurements on mice injected intravenously with a solution of CxP-AM showed that the compound did indeed localise in the brain, in contrast to analogous experiments using two other carboxy-proxyl derivatives, both of which exhibited much more diffuse distributions in the head. The authors point out that, because of its specificity and longevity in the brain, the CxP-AM agent should have potential for the determination of redox status of this organ in models of disease. 

Fugi MA, Wittlin S, Dong Y, Vennerstrom JL. (2010) Probing the anti-malarial mechanism of artemisinin and OZ277 (arterolane) with nonperoxidic isosteres and nitroxyl radicals. Antimicrob Agents Chemother 54 1042-1046. 

The name spin trapping was coined by Janzen, and derives from analogy with the use of stable nitroxyls as spin labels (or spin probes ) that provide spectroscopic information regarding their microscopic environment, a procedure pioneered by McConnell et alP ... 

Other probe molecules used for the EPR study of Ce02-based systems are NO and nitroxyl radicals [31, 32, 33] in this case, the neutral molecules themselves are paramagnetic, and give information without electron transfer. In the case of adsorbed NO, gz values are sensitive to the crystal field strength at adsorption sites of oxides in exactly the same way as in the case of O2 NO has been thus used to study the... 

NMR ( H, 13C, 15N) data show that there is a haem-histidine cross-link in cyanobacterial haemoglobins from Synechocyctis sp. PCC 6803 and Synecho-coccus sp. PCC 7002.199 Proton NMR spectroscopy was used to study the interaction of cytochrome c with micelles of sodium dodecyl sulfate.200 The transient HNO ( nitroxyl ) species can be trapped as an adduct with de-oxymyoglobin, i.e. Mb-HNO, with a proton chemical shift of the iron-bound HNO at 14.8 ppm.201 H and 31P NMR spectroscopy was used to probe the role of myoglobin as a scavenger of cellular NO in myocardium.202... 

The mobility of low molecular weight additives in the presence of fillers is important for the same reasons. Recent studies show that UV stabilizers are immobilized on the surfaces of filler particles. Nitroxyl radicals were used as spin probes in silica filled polymers. Experimental work confirms that absorption occurs on the OH groups of silica but it was shown that a certain minimum concentration of filler is required to trigger this absorption effect. 

Heterocyclic nitroxyl radicals as paramagnetic probes in adsorption and catalysis 81UK792. 

Nitriles, source of template p-Nitroaniline, adsorption Nitrogen industry, wastewater Nitromethane reagent Nitromethane, C NMR probe N-Nitrosamines degradation N-Nitrosamine removal Nitroxide, ditert-butyl Nitroxide EPR label Nitroxide EPR probe Nitroxide radical adsorption Nitroxyl radical probe NMR (see individual nuclei)... 

Spin probes I and II are studied in the system CTAB-hexanol-water [3,21]. Spin probe I, with its nitroxyl radical quite distant from the polar headgroup, probes the nonpolar region of the interface whereas spin probe II, with the nitroxyl radical close to the polar headgroup, explores the polar region of the interface. From the heights (/i) and the linewidths (A//) of the different multiplets (due to the electron-nitrogen hyperfine coupling), one can compute the rotational correlation times (t ) of these spin labels [84] from the relationship... 

Finally, the nitrogen hyperfine coupling (4, in gauss) is highly dependent on the medium polarity. The A values can therefore be used to characterize the local polarity in the microemulsions [66,68]. The A values of spin probes I and II (Table 8) show clearly that they are close to the hexanol value and are quite different from that obtained in water. The interface can therefore be assumed to be nonpolar, and no water penetration can be detected in our system. Note that even the nitroxyl group of spin probe II, although close to the polar headgroup, is not in direct interaction with the more polar interface. 

The spin probe method was one of the first methods used to evaluate the free volume in polymers [1,7]. It is based on the principle that the rotational frequency of spin probes, usually stable nitroxyl radicals such as TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) is sensitive to the free volume. The relatively complex correlation between spectral data and FV makes this method more suitable for qualitative comparison of different polymers than for quantitative analysis of the FV [1,8]. 

The dynamic lipid stmcture of membranes was studied by EPR - spectroscopy by use of computerized radio-spectrometer Bruker200D (Germany) and spin - probes two nitroxyl radicals 5- and 16-doxyl-stearic acids (5-and 16-DSA) from Sigma (USA). The radicals prepared in concentration... 

The spin probes 5- and 16-DSA are localized in the different regions of membrane lipids 5-DSA in surface lipids at depth of 8A° and hydrophobic nitroxyl radical 16-DSA penetrates in lipid bilayer to the depth more than 20A° [14, 16], A motion of 16-DSA can be characterized by rotation correlation time (x) by which a microviscosity value is estimated and anisotropic rotation of 5-DSA by order parameter (S) [15,16],... 

A technique related to spin labeling uses spin probes to monitor molecular motion. In this technique, a radical is synthesized that mimics as closely as possible the structure of the molecule under investigation. Again nitroxyl radicals are the most suitable candidates. An example of their use is in the study of polymer melts a spin probe is introduced into the polymer and then its rate of tumbling is measured as the polymer changes its viscosity and/or undergoes phase changes. 

Stable nitroxyl radicals have also been widely employed as spin probes for the study of relaxation and molecular dynamics of synthetic polymers. 

The amorphous regions were studied using EPR spectroscopy, which allows the estimation of the molecular mobility in disordered regions [17], A stable nitroxyl radical, 2,2,6,6-tetramethylpiperidine-l-oxyl (TEMPO) was used as a paramagnetic probe. The radical was introduced into the films from vapor at a temperature of 30 C. The rotational mobility of the radical probe was determined by the correlation time The following formula is used to calculate Eq. (2) r ... 

ESR techniques use nitroxyl radicals either dispersed in polymer matrix (spin probe) or covalently bonded to polymer chain (spin label) which are sensitive to the environment allowing molecular motion and microstructure of polymers to be identified from spectra (103). Quantitative methods of heterogeneous ESR spectra are divided into (J) outer hyperfine etrema, (2) signal intensities related to the relative concentration of the probe in different phases, and (3) simulation of the spectra. The presence of two well-separated outer maxima above the glass-transition temperature could be ascribed to two phases in natural rubber (104), miscible blends (105), immiscible blends (106), cross-linked polymers (107), and polyurethanes (108). ESR has used the measurement of the oxidation product to monitor the consumption of stabilizer in polypropylene (109). 

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