Standard conditions for the measurement of saturation-transfer ESR spectra

Hemminga, M.A.; Jager, P.A. de; Marsh, Derek; Fajer, Piotr G.

doi:10.1016/0022-2364(84)90295-6

Cited by 40 publications

(68 citation statements)

References 11 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Saturation transfer EPR spectra, where appropriate, were recorded according to the standardized protocol described in Ref. (14). Spectra were simulated according to the methods described in the Theory section.…”

Section: Methodsmentioning

confidence: 99%

“…Knowledge of the nuclear relaxation rate is therefore required to obtain the intrinsic electron spin-lattice relaxation time from progressive saturation EPR measurements. The database of T 1n -values for the normal 14 N-nitroxide spin labels is currently rather small. However, it does appear, except for very short rotational correlation times, that T 1n Յ T 1e , i.e., b Ն 1 (see, e.g., Ref.…”

Section: Appendix: Nuclear Relaxationmentioning

confidence: 99%

See 1 more Smart Citation

Relaxation Time Determinations by Progressive Saturation EPR: Effects of Molecular Motion and Zeeman Modulation for Spin Labels

Лившиц

Páli

Marsh

1998

Journal of Magnetic Resonance

Self Cite

View full text Add to dashboard Cite

The EPR spectra of nitroxide spin labels have been simulated as a function of microwave field, H1, taking into account both magnetic field modulation and molecular rotation. It is found that the saturation of the second integral, S, of the first harmonic in-phase absorption spectrum is approximated by that predicted for slow-passage conditions, that is, S approximately H1/1 + PH21, in all cases. This result is independent of the degree of inhomogeneous broadening. In general, the fitting parameter, P, depends not only on the T1 and T2 relaxation times, but also on the rate of molecular reorientation and on the modulation frequency. Calibrations for determining the relaxation times are established from the simulations. For a given modulation frequency and molecular reorientation rate, the parameter obtained by fitting the saturation curves is given by 1/P = a + 1/gamma2eT1 . Teff2, where Teff2 is the effective T2. For molecular reorientation frequencies in the range 2 x 10(7)-2 x 10(8) s-1, Teff2 is dominated by the molecular dynamics and is only weakly dependent on the intrinsic T02, allowing a direct estimation of T1. For reorientation frequencies outside this range, the (T1T2) product may be determined from the calibrations. The method is applied to determining relaxation times for spin labels undergoing different rates of rotational reorientation in a variety of environments, including those of biological relevance, and is verified experimentally by the relaxation rate enhancements induced by paramagnetic ions.

show abstract

Section: Methodsmentioning

confidence: 99%

Section: Appendix: Nuclear Relaxationmentioning

confidence: 99%

Relaxation Time Determinations by Progressive Saturation EPR: Effects of Molecular Motion and Zeeman Modulation for Spin Labels

Лившиц

Páli

Marsh

1998

Journal of Magnetic Resonance

Self Cite

View full text Add to dashboard Cite

show abstract

“…V2 is the second harmonic ESR absorption signal detected 900 out of phase with respect to the field modulation.) Standardized sample geometry and spectrometer settings and calibrations were employed (16,17). Integrals of the STESR spectra, normalized with respect to the intensity of the V1-mode spectra, were evaluated as described (18).…”

mentioning

confidence: 99%

Local translational diffusion rates of membranous Na+,K(+)-ATPase measured by saturation transfer ESR spectroscopy.

Esmann

Marsh

1992

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

View full text Add to dashboard Cite

Diffusion-controlled Heisenberg spin exchange between spin-labeled Na+,K(+)-ATPase [ATP phosphohydrolase (Na+/K(+)-transporting), EC 3.6.1.37] proteins has been studied by saturation transfer ESR spectroscopy in reconstituted membranes. Na+,K(+)-ATPase from the salt gland of Squalus acanthias was solubilized in a polyoxyethylene ether detergent, octa(ethylene glycol) dodecyl monoether. Part of the solubilized enzyme was covalently spin-labeled with a nitroxide derivative of indanedione and recombined with various proportions of the unlabeled enzyme while the native lipid/protein ratio was maintained. Purified membranes were then reconstituted from the various samples by precipitation with divalent ions. The reciprocal integrated intensities of the saturation transfer ESR spectra were found to increase linearly with the fraction of protein that was spin-labeled, and the gradient of the concentration dependence increased with increasing temperature over the range 4 degrees-25 degrees C. Comparison with theoretical analyses of the effects of weak Heisenberg spin exchange [Marsh, D. & Horváth, L. I. (1992) J. Magn. Reson. 97, 13-26] suggests that the effects on the saturation transfer ESR intensity are attributable to short-range diffusional collisions between the spin-labeled protein molecules. The effective value of the local translational diffusion coefficient is 1.8-2.9 microns2.s-1 at 15 degrees C, depending on the diffusion model used, which is much larger than the values obtained for the long-range diffusion coefficient in cells by photobleaching techniques. The temperature dependence of the translational diffusion is larger than expected but correlates with the anomalous temperature dependence of the rotational diffusion observed in the same system.

show abstract

“…ST-EPR spectroscopy was used in the motional region for R Ͼ 10 Ϫ7 s. This method is based on the diffusion and recovery of saturation between different portions of the powder spectrum in competition with field modulation (Hemminga, 1983). For ST-EPR spectroscopic measurements, the second harmonic quadrature absorption signal was detected under the following conditions: a fieldmodulation amplitude of 5 G, microwave power of 100 mW, and field-modulation frequency of 50 kHz (Hemminga et al, 1984). The phase was set with the self-null method (Thomas et al, 1976).…”

Section: Epr and St-epr Measurementsmentioning

confidence: 99%

Influence of Water Content and Temperature on Molecular Mobility and Intracellular Glasses in Seeds and Pollen

Buitink

Claessens

Hemminga³

et al. 1998

Plant Physiology

133

152

View full text Add to dashboard Cite

Although the occurrence of intracellular glasses in seeds and pollen has been established, physical properties such as rotational correlation times and viscosity have not been studied extensively. Using electron paramagnetic resonance spectroscopy, we examined changes in the molecular mobility of the hydrophilic nitroxide spin probe 3-carboxy-proxyl during melting of intracellular glasses in axes of pea (Pisum sativum L.) seeds and cattail (Typha latifolia L.) pollen. The rotational correlation time of the spin probe in intracellular glasses of both organisms was approximately 10 ؊3 s. Using the distance between the outer extrema of the electron paramagnetic resonance spectrum (2A zz ) as a measure of molecular mobility, we found a sharp increase in mobility at a definite temperature during heating. This temperature increased with decreasing water content of the samples. Differential scanning calorimetry data on these samples indicated that this sharp increase corresponded to melting of the glassy matrix. Molecular mobility was found to be inversely correlated with storage stability. With decreasing water content, the molecular mobility reached a minimum, and increased again at very low water content. Minimum mobility and maximum storage stability occurred at a similar water content. This correlation suggests that storage stability might be at least partially controlled by molecular mobility. At low temperatures, when storage longevity cannot be determined on a realistic time scale, 2A zz measurements can provide an estimate of the optimum storage conditions.

show abstract

Standard conditions for the measurement of saturation-transfer ESR spectra

Cited by 40 publications

References 11 publications

Relaxation Time Determinations by Progressive Saturation EPR: Effects of Molecular Motion and Zeeman Modulation for Spin Labels

Relaxation Time Determinations by Progressive Saturation EPR: Effects of Molecular Motion and Zeeman Modulation for Spin Labels

Local translational diffusion rates of membranous Na+,K(+)-ATPase measured by saturation transfer ESR spectroscopy.

Influence of Water Content and Temperature on Molecular Mobility and Intracellular Glasses in Seeds and Pollen

Contact Info

Product

Resources

About