Saturation-recovery

FIGURE 10.7 (a) Representative saturation-recovery signals of 14-PC in DMPC membranes containing... 

Here x from Equation 10.4 is changed to the two-membrane domain FOT and SLOT with the depth fixed (the same spin label is distributed between the FOT and SLOT domains). W(FOT) and W(SLOT) are oxygen transport parameters in each domain and represent the collision rate in samples equilibrated with air. Figure 10.9 illustrates the basis of the discrimination by oxygen transport (DOT) method, showing saturation-recovery EPR signals for 5-SASL in membranes... 

Kusumi, A., W. K. Subczynski, and J. S. Hyde. 1982b. Oxygen transport parameter in membranes as deduced by saturation recovery measurements of spin-lattice relaxation times of spin labels. Proc. Natl. Acad. Sci. USA 79 1854-1858. 

Subczynski, W. K., J. Widomska, A. Wisniewska, and A. Kusumi. 2007a. Saturation-recovery electron paramagnetic resonance discrimination by oxygen transport (DOT) method for characterizing membrane domains. In Methods in Molecular Biology Lipid Rafts, ed. T. J. McIntosh, Vol. 398, pp. 145-159, Totowa, NJ Humana Press. 

Whereas in the case of monomer siloxanes, Tj values may be measured by the inversion recovery method [1], we recommend the saturation recovery method for polymer siloxanes due to the very long measuring times. 

Figure 7 The saturation-recovery experiment. The dynamic range is equal to the equilibrium magnetization.

A number of pulse-sequence methods are available for measurement of Ti values, and those most commonly used are the methods of saturation recovery (s.r.F.t.),69,70 progressive saturation (p.s.F.t.),71 inversion recovery (i.r.F.t.),72 and the Freeman-Hill modification of in-... 

Fig. 5 Effect of varying relaxation delays between on- and off-resonance experiments in STD NMR experiments, a Experimental setnp for interleaved measnrements in STD NMR spectroscopy, n represents the nnmber of scans. The inter-scan delay Adi is varied while keeping on- and off-resonance freqnencies constant at -4 and -t300 ppm, respectively, b The resulting STD effects for the 0-methyl group of a-L-Fuc-O-methyl in the presence of RHDV VLPs. The equation that was used for non-linear least squares data fitting is based on the saturation recovery experiment [98], With Ti(iig) = 0.91 s as measured independently (unpublished results) and a Monte Carlo error estimation yields Ti(virus) = 10.06 0.41 s. This value does not directly correspond to a Tl relaxation time of the virus protons, because other factors also influence the observed relaxation [99]. According to these findings a relaxation delay Adi = 25 s was employed in all STD experiments. This results in a recovery of 92% of the virus resonance, and thereby reduces errors in epitope mapping that are introduced otherwise by non-homogeneous recovery of the binding site.

IR, inversion recovery SR, saturation recovery PS, progressive saturation STEAM, progressive saturation with stimulated echo acquisition mode SE, Hahn spin-echo sel. SE, frequency selective spin-echo. 

SR, saturation recovery ss ST, steady state saturation transfer SE, Hahn spin-echo. 

An interesting new experimental approach has been taken in order to separate overlapping EPR spectra as they appear e.g. in the multi Fe/S centre containing complex I. Inversion- and saturation-recovery measurements which allow to measure Ti relaxation times are used in a inversion-recovery filter which is subsequently applied to separate EPR signals on account of their Trdifferences. In addition, this filter can be used in conjunction with high-resolution hyperfine measurements e.g. by ESEEM and thus the separated centres can be characterized in depth.211... 

In subunit R2 of ribonucleotide reductase there is a tyrosyl radical (Y ) in close proximity to a di-iron cluster.100 In the protein from E. coli the EPR signal from Y can be observed up to room temperature. However, in the protein from yeast the Y signal broadens above 15 K and is not observable above about 60 K. Saturation recovery measurements at 140 GHz showed that at 60 K the spin-lattice relaxation rates for the Y signal in the yeast protein were about 2 orders of magnitude faster than for the E. coli protein. The temperature dependence of the relaxation enhancement was consistent with the activation energy for the first excited state of the di-iron cluster, so the relaxation enhancement was attributed to interaction with the di-iron cluster. Relaxation enhancements measured at 140 GHz showed little orientation dependence so the enhancement was assigned to isotropic exchange, which is different from the orientation-dependent dipolar interaction observed for the E. coli protein.100... 

Four spin-labelled derivatives of sperm whale metmyoglobin were prepared by site-directed mutagenesis.101 Cyanide anion or imidazole was added to prepare low-spin Fe(III). Iron relaxation rates were measured by saturation recovery or inversion recovery between 5 and 17 K and by analysis of the temperature-dependent contribution to the CW line widths of the iron signal at 20 to 160 K. The nitroxyl 7i values in spin-labelled Zn-substituted myoglobin were measured to provide values in the absence of interaction with the more rapidly-relaxing Fe(III). The full shapes of the nitroxyl saturation-recovery curves for the spin-... 

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