An overview of the various multiple-photon processes in electron paramagnetic resonance (EPR) spectroscopy is given. First, we describe different types of multiplephoton transitions that can be observed with monochromatic and bichromatic microwave fields in spin systems with unequally spaced energy levels and in twolevel systems. Then we discuss multiple-photon processes that are based on a bic...

The interaction of ATP with both iron-sulfur proteins of nitrogenase f rom Clostridium pasteurianum, azoferredoxin and molybdoferredoxin, has been studied by low-temperature EPR spectroscopy. ATP in the presence of Mg 2+ changes the rhombic EPR signal of azoferredoxin with g-values of 2.06, 1.94 and 1.87 to an axial signal, with g values of 2.04 and 1.93. The binding of two molecules of ATP per...

The paper supports the idea that NMR spectroscopy and imaging can enhance the classical EPR spin trapping techniques. NMR was used to follow and identify the diamagnetic products of DEPMPO/R• spin adduct breakdown. Oxyradical adducts of DEPMPO led to recycling of the spin trap, however, without sufficient long-term accumulation that would enhance EPR detection in vivo. Fluorinated derivative of...

The use of 90 degrees-out-of-phase first-harmonic absorption (V1'-) EPR to resolve the spectra from nitroxide spin labels with differing T1-relaxation times is described. Non-linear V1'-EPR spectra recorded under moderate saturation have sharper lines compared with the in-phase V1-EPR spectra, and amplitudes that preferentially enhance components with longer T1-relaxation. Discrimination betwee...

Solid-state sucrose is a well-known dosimetric system, which is capable of reliable dose estimates only at a considerable time after exposure. Immediately after irradiation at room temperature, its electron paramagnetic resonance (EPR) spectrum is dominated by contributions from unstable radicals, which are studied here using continuous-wave EPR and electron-nuclear double resonance (ENDOR) spe...

Electron paramagnetic resonance (EPR) spectroscopy has emerged as a valuable technique to study the structure and dynamics of nucleic acids and their complexes with other biomolecules. EPR studies require incorporation of stable free radicals (spin labels), usually aminoxyl radicals (nitroxides), at specific sites in the nucleic acids using site-directed spin labeling (SDSL). In addition to the...

Two kinds of microporous activated nanostructured carbons were studied by electron paramagnetic resonance (EPR) spectroscopy. They have different specific surface areas: 1500 m2/g (AC I) and 2500 m2/g (AC II). It was observed that the EPR spectra shapes and their temperature evolution between 300 K and 4 K were depending on the types of carbon sample. Roomtemperature spectra show dissimilar lin...

Free radicals in the original and sterilized caraway, curry, curcuma and cardamom were studied. An X-band (9.3 GHz) electron paramagnetic resonance (EPR) spectroscopy was the experimental technique. Effect of microwave power in the range of 2.2-70 mW on amplitudes, linewidths, and lineshape parameters of the EPR spectra was tested. Free radicals concentrations in the non- and sterilized herb sa...