The dynamic nature of the protons in H−ZSM-5 was examined by the temperature dependence of 1H MAS NMR in the range 298−473 K. The line width of 1H MAS NMR of acidic protons increased, and through maximum it decreased. The intensity of the spinning sidebands monotonically decreased, and they almost disappeared upon raising the temperature. This temperature dependence of the spectrum was explained by the thermal motion of protons. The correlation times and the activation energies for proton mobility were estimated. The estimated values of the activation energy are 17−20 kJ mol-1.

No abstract

The relation between the 1H chemical shift and the conformation of linear homopolypeptides and cyclic dipeptides in the solid state has been studied utilizing the 1H combined rotation and multiple pulse spectroscopy (CRAMPS) NMR method. It was found that the 1H chemical shift of the Hα signal of homopolypeptides depends on the secondary structure such as α-helix or β-sheet form, whereas those of the side-chain proton signals (Hβ, Hγ, Hδ, etc.) are almost independent of the secondary structure. The 1H chemical shifts of the Hα signal of homopolypeptides having the α-helix and the β-sheet forms were 3.9−4.0 ppm and 5.1−5.5 ppm, respectively. Accordingly, the 1H chemical shift of the Hα is very useful for conformational analysis of polypeptides in the solid state. Furthermore, it is shown that the 1H chemical shift of the Hα and the NH signals of cyclic dipeptides are sensitive to the ring conformation and the hydrogen bond length in the solid state.

No abstract