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This research applied the techniques of CP MAS 29 Si and 13 C, MAS high power decoupling 13 C, and MAS 1 H solid-state NMR, variable-temperature dependent 1 H NMR, 129 Xe NMR, low temperature 1 H diffusion, and two-dimensional exchange 129 Xe NMR to study the structure, dynamics, and interaction of the stationary phase and the xenon atoms in the Zorbax SB-C18 HPLC column material. The solid-state NMR experimental results showed the single binding type of alkylsilane groups, -Si(CH 2 -CH-(CH 3 ) 2 ) 2 (CH 2 ) 17 CH 3 , and the mobile alkyl chains on the silica surface at room temperature. The VT 1 H NMR and 1 H spin diffusion experiments suggested that at low temperatures a large portion of the alkyl chain molecules became immobile in the area where the density of the alkyl chains could be higher, while the rest of the alkyl chains remained somehow mobile in the areas with possibly lower density. The results of the VT 129 Xe NMR experiments showed the solvation of the xenon atoms in the stationary phase, the spatial occupation of the xenon atoms in the void spaces of the column material, and the diffusion of the xenon atoms in the column material. The two-dimensional exchange 129 Xe NMR results at low temperatures displayed the slow xenon diffusion between the pores and the voids between the particles. The two-dimensional exchange 129 Xe NMR spectra also indicate that the amorphous areas of the alkyl chains in the stationary phase experienced slow motions even at a temperature of -140 °C. This research illustrated that solid-state NMR of the stationary phase and 129 Xe NMR of the mobile phase give complementary information concerning the structure, dynamics, and interaction of column materials.

Conformations of the designed peptide Betanova in 42% trifluoroethanol/water (v/v) were explored. Circular dichroism (CD) observations provided no evidence for the presence of significant amounts of beta-structures in water, in TFE/water, or in ethanol/water. Nuclear magnetic resonance (NMR) diffusion experiments showed no significant difference in the hydrodynamic radius of the peptide in water and in 42% TFE/water. However, calculations indicated that the hydrodynamic radii of the triple-stranded beta-sheet, originally proposed for Betanova by Kortemme et al. (Science 1998, 281, 253-256), and a variety of partially folded forms of Betanova would be similar and likely could not be convincingly distinguished by diffusion experiments. Temperature coefficients (Deltadelta/DeltaT) of the peptide N--H chemical shifts are similar in water and 42% TFE/water, implying that most of these protons are highly solvent exposed in both solvents and likely do not participate in intramolecular hydrogen bonding interactions. Possible exceptions to this conclusion are the Lys9 and Lys15 residues, where a more positive coefficient may indicate that these residues are involved to some extent in local turn structures. Peptide proton-solvent fluorine intermolecular nuclear Overhauser effect (NOE)s at 25 degrees C were consistent with the presence of a mixture of conformations, which could include the triple-stranded beta-sheet structure as a minor component. At 0 degrees C, peptide-TFE NOEs indicated that TFE interacts strongly enough with many protons of Betanova that alcohol-peptide interactions persist for times of the order of nanoseconds, appreciably longer than the encounter time characteristic of mutual diffusion of TFE and the solute.

A novel laboratory method to synthesize clathrate hydrates in sealed glass tubes is described in this manuscript. It was known that the major obstacle in the synthesis of a gas hydrate is from the slow mass transport through the hydrate layer. To circumvent this problem in a sealed glass tube, we developed a temperature-gradient assisted gas-dissolved liquid-phase reaction. This method allows a clathrate hydrate start to form at the bottom of a glass tube and then grow through the diffusion of gas molecules from the gas phase passing through the liquid water phase to the water-gas hydrate interface. This method takes advantage of the fact that gases diffuse much faster in a liquid phase than in a gas-hydrate solid phase. Three examples to synthesize D 2 O/Xe, D 2 O/THF/Xe, and D 2 O/propane gas hydrates are given. The formations of the first two gas hydrates were verified with 129 Xe and 129 Xe T 1 NMR experiments, and that of the last one was verified with 13 C and 2 H-1 H QEDOR NMR experiments.

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