triacetoneamine-n-oxyl and 3-carbamoyl-2-2-5-5-tetramethyl-3-pyrroline-1-yloxyl

In rapid scan EPR the rapidly-changing magnetic field induces a background signal that may be larger than the EPR signal. A method has been developed to correct for that background signal by acquiring two sets of data, denoted as scan 1 and scan 2. In scan 2 the external field B

Topics: Cyclic N-Oxides; Electromagnetic Fields; Electron Spin Resonance Spectroscopy; Free Radicals; Magnetic Resonance Imaging; Nitrogen Oxides; Signal-To-Noise Ratio; Triacetoneamine-N-Oxyl

This paper describes a novel experiment on nitroxide radical spin labels using a multiarm EPR W-band bridge with a loop-gap resonator (LGR). We demonstrate EPR spectroscopy of spin labels by linear sweep of the microwave frequency across the spectrum. The high bandwidth of the LGR, about 1 GHz between 3 dB points of the microwave resonance, makes this new experiment possible. A frequency-tunable yttrium iron garnet (YIG) oscillator provides sweep rates as high as 1.8x10(5) GHz/s, which corresponds to 6.3 kT/s in magnetic field-sweep units over a 44 MHz range. Two experimental domains were identified. In the first, linear frequency sweep rates were relatively slow, and pure absorption and pure dispersion spectra were obtained. This appears to be a practical mode of operation at the present level of technological development. The main advantage is the elimination of sinusoidal magnetic field modulation. In the second mode, the frequency is swept rapidly across a portion of the spectrum, and then the frequency sweep is stopped for a readout period; FID signals from a swept line oscillate at a frequency that is the difference between the spectral position of the line in frequency units and the readout position. If there is more than one line, oscillations are superimposed. The sweep rates using the YIG oscillator were too slow, and the portion of the spectrum too narrow to achieve the full EPR equivalent of Fourier transform (FT) NMR. The paper discusses technical advances required to reach this goal. The hypothesis that trapezoidal frequency sweep is an enabling technology for FT EPR is supported by this study.

Topics: Algorithms; Cyclic N-Oxides; Electromagnetic Fields; Electron Spin Resonance Spectroscopy; Fourier Analysis; Indicators and Reagents; Microwaves; Nitrogen Oxides; Spin Labels; Triacetoneamine-N-Oxyl

Electron paramagnetic resonance imaging (EPRI) instrumentation, enabling the performance of three-dimensional spectral-spatial images of free radicals, has been developed to study spatially defined differences in tissue metabolism and oxygenation. Using this instrumentation 3D images of nitroxides in rat tail were obtained. The images visualize the arterial and venous vasculature in the tail segment. Based on the exchange broadening influence of oxygen on the EPR linewidth of nitroxides, we performed localized oxygen measurements in the in vivo rat. An oxygen concentration of 300+/-30 microM was measured in the arteries and 50+/-20 microM in the veins. These results demonstrate the feasibility of performing in vivo, non-invasive measurements and mapping of localized oxygenation in small animals using spectral-spatial EPR imaging techniques.

Topics: Animals; Arteries; Biophysical Phenomena; Biophysics; Cyclic N-Oxides; Electron Spin Resonance Spectroscopy; Female; Free Radicals; Image Processing, Computer-Assisted; Nitrogen Oxides; Oximetry; Oxygen; Rats; Rats, Sprague-Dawley; Spin Labels; Tail; Triacetoneamine-N-Oxyl; Veins