Electronic spin resonance signals

Johnson, K., Sutcliffe, L., Edwards, RH.T. and Jackson, M.J. (1988). Calcium ionophore enhances the electron spin resonance signal from isolated skeletal muscle. Bitxhim. Biophys. Acta 964, 285-288. 

If a molecule contains one or more unpaired electrons it is usually possible to detect an electron spin resonance signal and at a very low concentration of unpaired electrons, commonly 1018 spins with modem instruments. Several pieces of information can be obtained in this way. The number of unpaired spins can be found, the symmetry of the molecule in the region of the unpaired electron can be determined, and, if the unpaired electron is delocalized over nuclei with nuclear spins, then the extent of delocalization can be determined. Perhaps more importantly for our purpose, the rotational time of molecules can be determined from line shape studies. 

Table 10. Electron spin resonance signals of metalloproteins...

Wada, F., Higashi, T., Ichikawa, Y., Tada, K. and Sakamoto, Y. The relationship between electron spin resonance signals and haemoproteins of liver microsomes. Biochim. Biophys. Acta (1961+) 88, 65I+-655. 

Figure 8 shows the relationship between the hydrogenolytic behaviors and reduction time (52). The Mo(V) in the reduced catalyst is related neither to the catalytic activity nor to the hydrogenolytic behaviors. The electron spin resonance signal reaches a maximum within a very short reduction period, then drops and reaches a constant with continued reduction. This variation of Mo(V) concentration is compatible with the data obtained by Seshadri and Petrakis (67) and Massoth (55). The changes in the bja ratio and the catalytic activity with the time of reduction agree with the amount of Mo(IV) species reported by Massoth (55), as quoted in Fig. 8. 

Explaining just how this happens is far from simple. Electron spin resonance is a phenomenon of molecular structure in which high frequency energy is put into the molecular system and electron spin resonance signals emerge from the system. But not all compounds have an electron spin resonation to exhibit ESR activity a... 

Maruyama, T., Kataoka, N., Nagase, S., Nakada, H., Sato, H., and Sasaki, H. (1971). Identification of three-line electron spin resonance signal and its relationship to ascites tumors. Cancer Res. 31, 179-184. 

Vithayathil, A. J., Ternberg, J. L., and Commoner, B. (1965). Changes in electron spin resonance signals of rat liver during chemical carcinogenesis. Nature (London) 207, 1246-1249. 

Breslow and Newburg (57) pointed out that polymerization takes place mainly when the titanocene exists as titanium(IV). According to Henrici-Olive and Olive (58), the rate of polymerization decreases with increasing intensity of the electron spin resonance signals of the developing titanium(III) compound. 

Apply the crossover theorem, with reference to the figure in Example 14.5. The proportions of the iron-sulfur proteins in complexes I, II, and III with iron atoms in the Fe3+ and Fe2+ states can, in principle, be estimated from the electron spin resonance signals of the preparation of mitochondria. In the case of mitochondria oxidizing NADH in the presence of rotenone, application of the crossover theorem reveals that the iron atoms in the iron-sulfur proteins in complex I will become more reduced, while those in complex III will become more oxidized, in comparison to their states in the absence of rotenone. In the case of KCN-treated mitochondria, both sets of iron-sulfur proteins will become more... 

Light-induced Electron Spin Resonance Signals of Dyes on the Surface of Silver Bromide Microcrystals Photographic Effects... 

Direct experiments to examine the transbilayer movement of phospholipids (R.D. Kornberg, 1971) made use of spin-labeled analogs of PC in which the choline moiety was replaced with the tempocholine probe,, A -dimethyl-A -(l -oxyI-2, 2, 6, 6 -tetramethyl-4 -piperidyl)-ethanolamine (Fig. 2). These workers found that only the electron spin resonance signal generated by molecules in the outer leaflet of unilamellar liposomes could be rapidly quenched by ascorbate. The electron spin resonance signal from lipid molecules initially residing at the inner leaflet of liposomes was accessible to ascorbate with a r,/2 of >6.5 h, indicating slow transbilayer lipid movement (Fig. 3). 

Figure 8 shows the growth and decay curves (the kinetics) of these three phenomena—photoconductivity, light induced polarization and the electron spin resonance signal. All of them have the same unimole-cular time constants at 25°C. When the system is cooled to —100°, which has been done for the photoconductivity and the spin signal, they decay faster at the lower temperature but again they are parallel they have the same kinetic behavior. 

An additional argument in favor of the presence of intercalation is the temperature dependence of the line width of the electron spin resonance signal. Although the starting metaanthracite shows a derivative extremum line width of 12.5 1.0 gauss (G) that is independent of temperature, the C8K product shows a line width that depends upon temperature ... 

Recently, both polycrystalline and microcrystalline ( 200 A crystallite size) Si films have been investigated by ESR (Hasegawa ft a/., 1981b, 1983b). A dangling bond resonance in microcrystalline silicon films is observed at g = 2.0049. The spin density of this resonance is typically between 10 and 10 spins cm. In P-doped samples a conduction-electron spin-resonance signal is observed at = 1.997. 

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