Paramagnetic Relaxation in Dilute Potassium Ferricyanide

Rannestad, Andreas

doi:10.21236/ad0296786

Cited by 2 publications

(3 citation statements)

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“…It is of particular interest here that the Raman relaxation rates of all Kramer's doublets, such as low-spin Fe3+, are known to vary with temperature T as T9 at low temperatures. For covalently bound low-spin Fe3+ this has been confirmed using the diamagnetic crystalline host K3Co(CN)6 (10,11). The first evidence that anomalies existed for Fe3+ spin relaxation in proteins appears to have been published in 1973 by Mailer and Taylor (3), who studied single crystals of ferricytochrome c at a microwave frequency of 24 GHz.…”

Section: General Resultsmentioning

confidence: 89%

Protein conformation from electron spin relaxation data

Allen

Colvin²,

Stinson³

et al. 1982

Biophysical Journal

118

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Electron spin relaxation data from five ferric proteins are analyzed in terms of the fractal model of protein structures. Details of this model are presented. The results lead to a characterization of protein structures by a single parameter, the fractal dimension, d. This structural parameter is shown to determine the temperature dependence of the Raman electron spin relaxation rate, which varies as T3 + 2d. Computations of d are made using x-ray data for 17 proteins. The results range from d = 1.76 for lysozyme to d = 1.34 for ferredoxin. These values are compared with values of d obtained from the present electron spin relaxation data on five ferric proteins. Typical results are d = 1.34 +/- 0.06 from relaxation data and 1.34 +/- 0.05 from x-ray data for ferredoxin; d = 1.67 +/- 0.03 from relaxation data and 1.66 +/- 0.05 from x-ray data for ferricytochrome c. The data thus support the theoretical model. Applications of this spin resonance technique to the study of changes in protein conformation are discussed.

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Section: General Resultsmentioning

confidence: 89%

Protein conformation from electron spin relaxation data

Allen

Colvin²,

Stinson³

et al. 1982

Biophysical Journal

118

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“…For the small direct and Raman relaxation rates assumed in figure 3, a helium bath will keep the temperatures of the resonant and remaining phonon modes constant, which undoubtedly is the reason that the two relaxation rates are found, experimentally [Rannestad and Wagner, 1963; Davids and Wagner, 1964;Baker et al, 1956;Paxman, 1961;Bray et al, 1962], to be additive, as we assume in this section.…”

Section: Theorymentioning

confidence: 99%

“…havior of the inverse spin temperature as given by eqs (25a) and (27a). The curves in figure 3 are based upon parameter values appropriate to the spin concentration and splitting used in a paramagnetic crystal which has been studied extensively [Rannestad and Wagner, 1963; Davids and Wagner, 1964;Baker et al, 1956;Paxman, 1961;Bray et al, 1962]. This is the crystal K 3 Co(CN) 6 doped with Fe 3+ ion.…”

Section: Theorymentioning

confidence: 99%

Effects of finite lattice capacity on spin lattice relaxation :

Peterson¹

1967

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The transient magnetic behavior of a paramagnetic substance, after an initial disturbance, is considered theoretically for a variety of situations in which the lattice temperature rises as a result of energy flow from the magnetic (electron spin) system. The relaxation mechanisms considered are the direct process, involving interaction between spins and the resonant-phonon modes, and a T 9 Raman process, involving the remaining phonon modes. It is first assumed that the resonant and remaining modes are strongly coupled to each other, and that the helium bath has been removed (helium temperatures are assumed). The resulting transient behavior typically does not differ much from exponential relaxation (the rate increases somewhat during the relaxation), but the difference should be experimentally observable, particularly if the resonance line is inverted initially.Next, the opposite extreme is consideredthat in which the resonant and remaining modes are totally uncoupled; the helium bath is again assumed to have been removed. Two dramatic effects can then occur, depending upon initial conditions. One is the rapid decay to saturation from initial inversion, due to an avalanching creation of resonant phonons by the spins. The second is the pronounced inhibition of the subsequent decay, with the spins remaining near saturation. This decay rate is typically very much slower than the Raman rate, and is due to the flow of the resonant-phonon energy back into the spin system as the spin energy flows into the remaining lattice. Eventually the rate increases to the Raman rate characteristic of the final lattice temperature. Because of inelastic phonon scattering at crystal boundaries, which couples the phonon modes together, this effect of inhibited decay may be difficult to observe.Finally, we consider the case of spins coupled only to the resonant phonons, which in turn are coupled to a constant temperature bath, whether this be the helium or the remaining modes. Recent phonon avalanche experiments are discussed in this context. It is pointed out that such experiments, performed in the absence of a bath, may provide a reliable measurement of inelastic phonon-boundary scattering.

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Paramagnetic Relaxation in Dilute Potassium Ferricyanide

Cited by 2 publications

References 1 publication

Protein conformation from electron spin relaxation data

Protein conformation from electron spin relaxation data

Effects of finite lattice capacity on spin lattice relaxation :

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