High Pressure NMR :供参考 1.The Use of High Pressure NMR for the Determination of Phase Behavior for Select Binary Solvent Systems.
High pressure NMR has proven itself to be a valuable technique for the study of supercritical fluid solutions. In this manuscript, we describe the extension of high pressure NMR to the investigation of the phase behavior for two binary solvent systems; ethylene/methanol and propane/methanol. The phase behavior was investigated as a function of pressure and temperature, with the molar composition of both phases being determined simultaneously, in situ, in a high pressure capillary NMR cell. The hydrogen bonding behavior of the alcohol in both phases determined in these experiments, provides important physiochemical information regarding solvent interactions occurring in both the liquid and vapor phase. High pressure NMR proves to be an efficient method for obtaining vapor liquid equilibrium data and critical conditions of binary solvent systems. This methodology should also be applicable to ternary systems as well as to more extreme solvent systems, such as supercritical water. 2.High-resolution, high-pressure NMR studies of proteins.
Advanced high-resolution NMR spectroscopy, including two-dimensional NMR techniques, combined with high pressure capability, represents a powerful new tool in the study of proteins. This contribution is organized in the following way. First, the specialized instrumentation needed for high-pressure NMR experiments is discussed, with specific emphasis on the design features and performance characteristics of a high-sensitivity, high-resolution, variable-temperature NMR probe operating at 500 MHz and at pressures of up to 500 MPa. An overview of several recent studies using 1D and 2D high-resolution, high-pressure NMR spectroscopy to investigate the pressure-induced reversible unfolding and pressure-assisted cold denaturation of lysozyme, ribonuclease A, and ubiquitin is presented. Specifically, the relationship between the residual secondary structure of pressure-assisted, cold-denatured states and the structure of early folding intermediates is discussed.
High-Pressure Nuclear Magnetic Resonance Since the mid 90's work at PNNL has focused on the investigation of supercritical fluid solutions using high-pressure nuclear magnetic resonance (NMR). There are numerous experimental techniques that have been used to investigate supercritical fluids. These range from FTIR, UV-Visible, fluorescence, ESR, and x-ray spectroscopies. NMR is a technique that has seen limited application to supercritical fluid solvents due to the specialized need for a high pressure, non-magnetic probe and its associated electronics. There have been different successful solutions to a functioning high pressure NMR probe ("A new apparatus for the convenient measurement of NMR spectra in high-pressure liquids", Yonker, C.R.; Zemanian, T.S.; Wallen, S.L.; Linehan, J.C.; Franz, J.A., J Magn Res A 1995, (113):102-107) and each of these probe designs has its own strengths and weaknesses. Overall, NMR is an information-rich spectroscopic technique that can describe the solvent environment about a solute molecule, determine self-diffusion coefficients, ascertain molecular structure, measure hydrogen bonding in solution, and describe molecular clustering as a function of density. NMR can provide important molecular level information about the density dependence of rotational and translational dynamics in supercritical fluid solutions. Similarly, high-pressure kinetics and chemical equilibria can be investigated by the use of NMR. In situ laser photolysis in a ultra-high pressure NMR cell
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