QENS data

Pulsed field gradient (PFG)-NMR experiments have been employed in the groups of Zawodzinski and Kreuer to measure the self-diffusivity of water in the membrane as a function of the water content. From QENS, the typical time and length scales of the molecular motions can be evaluated. It was observed that water mobility increases with water content up to almost bulk-like values above T 10, where the water content A = nn o/ nsojH is defined as the ratio of the number of moles of water molecules per moles of acid head groups (-SO3H). In Perrin et al., QENS data for hydrated Nation were analyzed with a Gaussian model for localized translational diffusion. Typical sizes of confining domains and diffusion coefficients, as well as characteristic times for the elementary jump processes, were obtained as functions of A the results were discussed with respect to membrane structure and sorption characteristics. ... 

In Fig. 18 the self-diffusivities obtained by different experimental techniques are compared. It appears that in both the absolute values and the trends in the concentration dependence, the QENS data, the PFG NMR results, and the data derived from sophisticated uptake experiments using the piezometric or single-step frequency-response techniques agree. Nevertheless, disagreement with some sorption results has to be stated. Additional information on the molecular reorientation of benzene in zeolite X has been obtained by QENS and NMR lineshape analysis. 

The same conclusions as drawn from QENS data can be drawn from NMR lineshape analysis. The temperature influence on the NMR lineshape of benzene sorbed on NaX is shown in Fig. 19. As in the case of... 

The QENS data of Hewish et al. (31 b) and of Salmon et al. (66) show that the influence of ions on the dynamics of the water molecules extends into the second shell and beyond. 

Fig. 5 The Q dependence of the HWHM of the Lorentzian function obtained from the experimental QENS data of propane in Na-Y, fitted with different model functions. Adapted from [19]...

In the case of cyclopropane in AIPO4-5 and methane in ZSM-48, however, the QENS data also show the typical scattering pattern of singlefile diffusion [101,102]. It is interesting to note that for methane in ZSM-48, a transition from normal diffusion (at low concentrations, D... 

Figure 9 shows the ambient pressure values of (tt) (QENS data) (Fig. 9a) and the inverse of the self-diffusion coefficient of water 1 /D measured by NMR (Fig. 9b) for the fully hydrated MCM-41-S samples with pore diameters of 14 A and 18 A. 

Comparison between MD simulation and QENS data [17] (inset). 

It is important to stress that the combination of both the low-Q QENS data and MD simulations allows us to understand on a molecular basis the onset of the reversible folding and the successive irreversible denaturation. In particular, by considering these results and the cited NMR and FTIR experimental data [15,19] it is possible to conclude that the denaturation of the protein and the dynamic crossover in its hydration water are causally related. In fact, all of their coincidences suggest that this high-r crossover could be a significant factor in the reversible denaturation process. We also note that the organization of water/biomolecules... 

Figure 7.7 Arrhenius plot of reciprocal correlation times extracted from the longitudinal muon spin relaxation measurements of benzene chromium tricarbonyl compared with QENS data [4]. Reproduced from Hyperfine Interactions 106, 27-32 (1997), U. A. Jayasooriya, I A. Stride, G. M. Aston, G. A. Hopkins, S. F. J. Cox, S. P. Cottrell and C. A. Scott, Figure 2, Kluwer, with kind permission of Kluwer Academic Publishers.

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