TEMPONE

Table 5, Average polymer chain concentration (ape), polymer swellability (S), rotational correlation times of TEMPONE (r) and self-diffusion coefficient of methanol (Zf) in the swollen 2,2% Pd catalysts.

Water-soluble iminoxyl free radical - 2,2,6,6,-tetramethyl-4-oxo-piperidin-l-oxyl (commercial trade name TEMPON) was used as a paramagnetic probe. 

ESR-spectra of TEMPON degradation in erythrocytes and hepatocytes were studied. The degradation was caused by the chemical processes presented in Schemes 2.1 and 2.2. 

Fig.Zl (a) Influence of CNT concentration in presence of Kj[Fe(CN)J on intensity of the ESR spectra of the paramagnetic label TEMPON control (without CNT) (7) and adding CNT to blood erythrocytes at 0.01 (2), 0.05 (5), 0.1 (4) and 0.2 (5) mg/mL (b) kinetics of the ESR signal intensity decay of the paramagnetic label in liver homogenate after 4 h inoculation 1 - control (without CNT), 2 - in presence of CNT with concentration 0.2 mg/mL...

Pulse Experiments. PELDOR studies of Fremy s salt in 1 1 water glycerol demonstrated that the spatial distribution of these radicals with a 2 — charge was significantly different than for the neutral tempone radical, which was attributed to electrostatic repulsion.43... 

Steinhoff et al. (1989) measured the temperature and hydration dependence of the ESR spectra of hemoglobin spin-labeled at cysteine )8-93. They observed the critical temperature near 200 K, as described above, and the sensitivity of the spectrum to hydration level. Spectrum simulations suggested that there were two types of motion in the dry protein, a fast vibration of the label within a limited motion cone upon the addition of water, a hydration-dependent motion assigned to the fluctuations of the protein, of correlation time 10 sec in samples of high hydration and at 300 K. The temperature dependence of the motional properties of a spin probe (TEMPONE), diffused into hydrated single crystals, closely paralleled the motional properties of the label. This was taken to be evidence for coupling between the dynamical properties of the protein and the adjacent solvent. 

ESR spectra (Rupley et al., 1980) of lysozyme samples containing a noncovalendy bound spin probe, TEMPONE, are strongly dependent... 

Fig. 20. ESR spectra of TEMPONE noncovalently bound to lysozyme, for hydration levels of 0.02-1.33 h. The mole ratio of TEMPONE was 0.018 at this low value spin-spin interactions do not make a significant contribution to the measurements. All measurements were made at 24°C. From Rupley et at. (1980).

Fig. 21. Values of the correlation time, r, for TEMPONE noncovalently bound to lysozyme in the variable environment as a function of hydration level. Error bar shows the range of values that gives acceptable simulated spectra. Fraction of TEMPONE in the variable environment is 0.5 0.2 at high hydration. From Rupley etal. (1980).

Fig. 30. Comparison of ESR and enzyme activity changes with hydration. Effect of hydration on lysozyme dynamic properties. (Curve f) Log rate of peptide hydrogen exchange. (Curve g) , Enzyme activity (log uo) O, rotational relaxation time (log t ) of the ESR probe TEMPONE. From Rupley et al. (1983).

Above 0.2—0.25 h the rotational motion of the spin probe TEMPONE grows explosively, with an apparent 15th-order dependence on water... 

There appears to be no single pattern describing the hydration dependence of enzyme activity. Lysozyme activity is correlated with the unfreezing of surface motion at 0.25 A and also with the onset of surface percolation. There are changes in activity above 0.38 A, such as the changes found for rotational motion of TEMPONE. The hydration threshold for chymotrypsin activity, at 0.12 A, is substantially lower than that for lysozyme. A correlation with percolation is an attractive, but untested, possibility. 

Electron Spin Resonance. ESR spectra (Figure 4) were measured for partially hydrated powders of lysozyme containing a nltroxlde spin probe, TEMPONE. Figure 5 shows the change with hydration level of a parameter which characterizes the relative amplitudes of various spectral lines. 

Figure 5. Ratio of heights of hyperfine lines (1 /1,) from 0.02 to 0.36 h for Tempone noncovalently bound to lysozyme (mole fraction 0.018)...

Patel NS, Chatterjee PK, Chatterjee BE et al. The stable nitroxyl radical TEMPONE reduces renal dysfunction and injury mediated by oxidative stress in the rat kidney. Free Rad Med Biol 2002 33 1575-1589. 

Further splittings of the main resonance line, due to hyperfine interactions, are (to first order) independent of the microwave frequency. Measurements at different frequencies can therefore clarify if an observed spectrum is split by Zeeman interactions (different g-factors) or other reasons. The example reported in Fig. 4.6 due to Tempone (2,2,6,6- tetramethylpiperidine-N-oxyl) spin label illustrates how spectral features caused by hyperfine structure and g-anisotropy can be differentiated by measurements at X and W-bands [16]. 

Fig. 4.6 9.0 (a) and 94.4 GHz (b) ESR spectra from 0.05 mM solution of perdeuterated 2,2, 6,6 -tetramethyl- 4-piperidone-I-nitroxide (TEMPONE) in toluene-ds at 130 K. Approximate principal g- and hyperfine (A)-tensors are indicated. The figure is reproduced from [16] with permission from the Royal Society of Chemistry... 

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