Electron Spin Resonance Studies of Radical Pairs Formed in Hydroxyurea by X Irradiation at Low Temperatures

1969 ◽  
Vol 50 (10) ◽  
pp. 4368-4372 ◽  
Author(s):  
Keith Reiss ◽  
Howard Shields
Keyword(s):  
Electron Spin Resonance ◽  
Electron Spin ◽  
Low Temperatures ◽  
Radical Pairs ◽  
Spin Resonance ◽  
X Irradiation

Über die Radikalkonzentration von Rattenleber-Mitochondrien in Abhängigkeit von verschiedenen Faktoren

1968 ◽  
Vol 23 (6) ◽  
pp. 798-803 ◽  
Author(s):  
M. Waldschmidt ◽  
H. Mönig ◽  
J. Schole
Keyword(s):  
Free Radicals ◽  
Electron Spin Resonance ◽  
Electron Spin ◽  
Mitochondrial Protein ◽  
Yeast Cells ◽  
Whole Body ◽  
Resonance Spectroscopy ◽  
Control Value ◽  
Spin Resonance ◽  
X Irradiation

The concentration of free radicals in freshly prepared ratliver-mitochondria was investigated under different conditions with the aid of electron spin resonance spectroscopy. The electron spin resonance signal at g=2.004 was measured at 77 °K and related to the weight in milligrams of mitochondrial protein. The concentration of free radicals increases with rising body weight or, in other words, with decreasing growth rate of the animals. A plateau is reached with about 1013 radicalcenters per mg protein for grown animals. The concentration of free radicals is 150% of the control value after fasting for 24 hours, whereas it is below the detectable level in cells of ascites hepatoma. We conclude that the concentration of free radicals determined at g = 2.004 is a function of mitochondrial activity. After whole body x-irradiation with a dose of 900 R, a significant decrease of 20% of the signal amplitude was measured. Increasing the dose to 1800 R did not decrease the radical concentration further. These results might be connected with the diminished activity of some flavin enzymes observed in liver mitochondria after x-irradiation in vivo. In further experiments we have incubated the mitochondria in vitro with various inhibitors of flavin enzymes. The individual inhibitors (ammonium-ions, KCN, acetonitrile, glucose) and also malonate reduce the concentration of free radicals to 80% of the control value in the mean if the particles are incubated at 37 °C for 5 minutes. The effect of malonate adds to the effects of the other inhibitors. The inhibitory effect of 2,4-dinitrophenol develops only after a longer incubation time. These results are discussed in connection with the influence of the same inhibitors on the Pasteureffect of yeast cells. Some specific inhibitors of the respiratory chain (Amytal, antimycin A, oligomycin) also diminish the concentration of free radicals.

Electron spin resonance studies of oriented NO2 and NF2 in inert matrices at low temperatures

1970 ◽  
Vol 48 (5) ◽  
pp. 805-817 ◽  
Author(s):  
C. A. McDowell ◽  
H. Nakajima ◽  
P. Raghunathan
Keyword(s):  
Electron Spin Resonance ◽  
Electron Spin ◽  
Low Temperatures ◽  
Hyperfine Splitting ◽  
Preferential Orientation ◽  
Paramagnetic Species ◽  
Host Matrix ◽  
Argon Matrix ◽  
Spin Resonance ◽  
Inert Matrices

Preferentially oriented NO2 and NF2 in inert matrices have been studied in some detail by electron spin resonance methods at 4.2 °K. Methods are discussed which may optimize the degree of preferential orientation of the paramagnetic species in appropriate matrices. The results demonstrate that while neon is the best host matrix for orienting NO2, argon is to be preferred for NF2. The g-values and hyperfine splitting data have been accurately determined and are compared with earlier values. Motional processes are suggested to explain the spectra obtained for NF2 in an argon matrix in the temperature range 4–30 °K.

ELECTRON SPIN RESONANCE SPECTRA OF 15N-CENTERED RADICALS AT LOW TEMPERATURES: I. THE RADICAL NH3+ TRAPPED IN NH4ClO4

1965 ◽  
Vol 43 (5) ◽  
pp. 1012-1016 ◽  
Author(s):  
M. Fujimoto ◽  
J. R. Morton
Keyword(s):  
Electron Spin Resonance ◽  
Electron Spin Resonance Spectrum ◽  
Ammonium Perchlorate ◽  
Electron Spin ◽  
Rotational Motion ◽  
Low Temperatures ◽  
Resonance Spectrum ◽  
Radical Theory ◽  
Spin Resonance

The electron spin resonance spectrum of NH3+ trapped in ammonium perchlorate (95% 15N) was examined at 300 °K, 77 °K, and 4 °K. The spectra are interpreted in terms of π-radical theory, and demonstrate the different stages in the freezing-out of the rotational motion of the ion.

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