Proton solvent, relaxation dispersion

Binding of Mono- and Oligosaccharides to Concanavalin A as Studied by Solvent Proton Magnetic Relaxation Dispersion... 

Relaxation Measurements. Measurements of the magnetic fieldz dependence of the solvent water proton relaxation rate (T] l), i.e., nuclear magnetic relaxation dispersion (NMRD), were made by the field cycling method previously described (9,10). 

There are two separate contributions to the solvent relaxation rate that are introduced by the presence of solute protein, both of which add to the field-independent relaxation rate of protons in pure solvent the larger NMRD contribution, labelled A, disperses at low fields with an inflection generally between 0.1 and 10 MHz the smaller contribution, labelled D, is known to... 

Figure 3. Variation with molecular weight of the inflection frequency ve (Equation 1) of the relaxation dispersion of solvent protons fen- solutions of macromolecules at 25°C.

Roose et al. (1996) studied the magnetic-field dependence of the proton spin-lattice relaxation time Tj (referred to as nuclear-magnetic-relaxation dispersion) in aqueous colloidal silica containing paramagnetic Mn + ions (Figure 1.112). The experimental relaxation rate of solvent protons in aqueous colloidal silica suspensions containing Mn + ions can be expressed as a weighted mean of several contributions ... 

Permanent or thermoreversible cross-links mediate the opposite effect on chain dynamics compared with dilution by a solvent instead of releasing topological constraints by dilution, additional hindrances to chain modes are established by the network. With respect to NMR measurands relatively large cross-link densities are needed to affect chain modes visible in the experimental time/frequency window, as demonstrated with proton spin-lattice relaxation dispersion of polyethylene cross-Unked by 10-Mrad irradiation with electron beams [123] and with styrene-butadiene rubbers [29]. However, there is a very strong effect on the dipolar correlation effect which probes much slower motions and can therefore be used favorably for the determination of the cross-Hnk density [29, 176, 177]. 

The NMRD profile of chromium(III) aqua ion (Fig. 18) is characterized by slow exchanging water protons, as clearly shown by the fact that the solvent proton relaxivity at low fields increases with increasing the temperature. The occurrence of slow exchange hinders any increase in relaxivity below 300 K, thus explaining the fact that the contact dispersion disappears in the low temperature profiles, whereas it is well shown in the high temperature profiles, as already discussed in Section I.C.8. 

The structural information derived from relaxation enhancement studies depends somewhat on the model chosen to describe the interaction of solvent protons with the protein molecules. For example even if the experiments indicated that the dispersion of Tfpr were essentially determined by the correlation time for rotational tumbling of the protein the tumbling of the hydration waters would not necessarily have to be restricted to that of the entire hydrated protein. Evidence was found that fast intramolecular tumbling about an axis fixed with respect to the surface of the hydrated species reduced the proton and O17 nuclear relaxation rates even in extremely stable aquocomplexes of Al3+ and other metal ions (Connick and Wiithrich (21)). The occurrence of similar... 

Figure 1. Dispersion of 7/T/, the magnetic relaxation rate of solvent water protons, for a 65 mg/mL solution of alcohol-dehydrogenase from yeast, 160,000...

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