Field gradient NMR techniques

Zhang O, Kay LE, Olivier JP, Forman-Kay JD. Backbone 11 and 15N resonance assignments of the N-terminal SFI3 domain of drk in folded and unfolded states using enhanced sensitivity pulsed field gradient NMR techniques. J Biol NMR 1994 4 845-858. 

Investigations of self-diffusion coefficients have been carried out by Parravano et al. (252) and Karger et at. (259, 275-278) using pulsed-field-gradient NMR techniques. The residence time t of a molecule in a particular... 

As shown above, the pulsed field gradient NMR technique was first described by Tanner and Stejskal [1,2]. In addition to their work on unrestricted diffusion they also performed theoretical analyses of restricted diffusion and tested their results on octanol-in-water emulsions stabilized by surfactants. 

The pulsed field gradient NMR technique can be readily used for the determination of the water droplet size distribution in W/O emulsions or the oil droplet size distributions in O/W emulsions. Important advantages are the non-invasive nature, the ease of sample preparation, and the feet that pulsed field gradient NMR measures the droplet size distribution of the bulk in contrast with microscopic methods which estimate the size distribution of the surface. Both the proposed matrix method and the iterative curve fitting procedure can be successfully applied in a factory environment. The method can be implemented on a high as well as on a low resolution NMR spectrometer. 

In most cases, structural characterization of carbosilane dendrimers is accomplished by multinuclear one-dimensional NMR spectroscopy (1H, 13C and 29Si). However, as larger dendrimers are characterized standard spectroscopic methods become less useful due to the overlap of signals. This problem has been elegantly circumvented as described in a recent paper by Tessier, Rinaldi and coworkers56. In this paper the researchers described the use of 1 H/13C/29Si triple resonance, 3D and pulse field gradient NMR techniques to... 

For comparison, we have also reported in Fig. 3 the data obtained by Appel and Fleischer [51] with PDMS at 60°C, using the pulsed field gradient NMR technique to measure the self-diffusion coefficient. Except for the slightly higher values due to the increased temperature, it is remarkable that exactly the same trends are observed for the two sets of data corresponding to N = P. 

The flow through an abrupt contraction " or a step stenosis was demonstrated. The flow of liquid crystalline hydroxypropyl cellulose aqueous solutions, where polymer was flowing through an abrupt contraction, was imaged by pulsed field gradient NMR techniques. Flow velocity was determined in the case of the flow through step stenosis. ... 

In this work the applications of three dimensional (3D) solution NMR techniques for characterizing the structures of synthetic polymers and dendrimers are illustrated, including the characterization of polymer chain-end structure, monomer sequence, stereosequence, and branching. The utility of triple resonance and pulsed field gradient NMR techniques in these research endeavors are discussed. 

Peschier, L. J. C., Bouwstra, J. A., de Bleyser, J., Junginger, H. E., and Le5de, J. C., 1993, Water mobility and structure in poly[2-hydroxyethylmethacrylate] hydrogels by means of the pulsed field gradient NMR technique. Biomaterials 14 945-952. 

Jung, D.-M., J.S. de Ropp, S.E. Ebeler, Application of pulsed field gradient NMR techniques for investigating binding of flavor compounds to macromolecules, J. Agric. Food Chem., 50(15), p. 4262, 2002. 

Steady (SFG) and pulsed (PEG) field gradient NMR techniques have been widely used to study the self-diffusion of polymers in melts, dilute and semidilute solutions. The NMR self-diffusion measurements are based on local differences in Larmor precession frequencies when applying a... 

It should be noted that the radiotracer and pulsed field gradient NMR techniques measure the self-diffusion coefficient of water, Ds, rather than the Fickian or interdiffusion coefficient of water through the polymer membrane, D, and some correction is required, because it is the Fickian water diffusion coefficient that is the proper transport property to use in macroscopic studies of water diffusion [17]. The relationship is ... 

Advances in experimental techniques, including pulsed-field gradient NMR, and theoretical methods, including volume averaging, macrotransport, and variational methods, that may lead to the resolution of a number of the fundamental issues in gel electrophoresis and to improvements in the practical application of electrotransport in polymeric media... 

Lateral diffusion of phospholipids in model membranes at ambient pressure has been studied over the years by a variety of techniques including fluorescence recovery after photobleaching (FRAP), spin-label ESR, pulse field gradient NMR (PFG-NMR), quasielastic neutron scattering (QENS), excimer fluorescence and others.In general, the values reported for the lateral diffusion coefficient (D) range from 10 to 10 cm /s in the... 

Field gradient NMR has been employed to determine the self-diffusion coefficient of a Pluronic triblock, and the hydrodynamic radius has been compared to DLS measurements on the same system (Almgren et al. 1992). NMR was found to give a somewhat lower value for the hydrodynamic radius than DLS. However, at infinite dilution the values obtained from the two techniques are the same. A similar observation has been made for eye I o - PB027P H 0,44 in aqueous solution (Yu et al. 1996c). Tin s effect has been attributed (Almgren et al. 1995) to the difference in dynamic averaging for the DLS and NMR experiments. In DLS,... 

Fleisher et al. [12] studied the self-diffusion of oil and water in rape seeds. The selfdiffusion of oil was found to be completely restricted. The experiments could be explained in toms of the model of diffusion within spherical droplets and a Gaussian mass distribution of the droplet radii. At the same time Van den Enden et al. [9] introduced the technique described above. It is a rapid method for the determination of water droplet size distributions in spreads by using low resolution pulsed field gradient NMR. Their method was based on the recognition that a set of echo attenuation values (R) as a function of the field gradient pulsed width, obtained under conditions where R is independent of the time allowed for diffusion, contains all the necessary information on the water droplet size distribution (see above). A log-normal distribution of water droplet sizes was assumed. 

Diffusion coefficients of nucleic acids in solutions and gels have been accurately measured with the development of advanced laboratory techniques, such as pulsed field-gradient NMR and FRAP (Lapham et al., 1997 Pluen et al., 1999 Politz et al., 1998). These data may provide some semi-quantitative information applicable to interstitial transport of nucleic acids in tumor tissues. 

General overview of several studies of transport and intermolecular interactions in compressed supercritical fluids is presented. The unique aspects of the instrumentation used in these studies are emphasized. First, the results of NMR studies of self-diffusion in supercritical ethylene and toluene are discussed. These experiments used the fixed field gradient NMR spin-echo technique. Second, the novel NMR technique for the determination of solubility of solids in supercritical fluids is described. 

Pulsed field gradient NMR (PFG-NMR) is a powerful, nondestructive technique of measuring self-diffusion coefficients in a colloidal dispersion [69-71]. Molecules associated with an aggregate or a particle will diffuse more slowly than their free dissolving state. More specifically, when a water-soluble species is partially adsorbed onto an abrasive particle, the measured overall diffusion coefficient (D ) of the species is decreased. If the diffusion coefficient of the free dissolving species can be measured in the absence... 

Analyzing the self-diffusion behavior of guest molecules in a microporous catalyst by the combined application of pulsed-field gradient NMR selfdiffusion techniques reveals the spatial distribution of transport resistances over the catalyst particles. In the case of coke deposits on ZSM-5, the distribution of carbonaceous residues over the crystal was found to be a function of the crystal morphology, the time onstream, and the chemical nature of the coke-producing reactant. In the case of ZSM-5 modified by H3PO4, the spatial distribution of the P compounds over the ZSM-5 crystals can be determined by self-diffusion measurements. Location of transport hindrances in a zeolite framework is based on self-diffusion measurements, in... 

Mesoporous structures are commonly characterized with diffraction, electron microscopy methods [14], and gas sorption techniques. The ensemble diffusion behavior of small molecules has been examined with pulsed-field gradient NMR spectroscopy [15] and neutron scattering [16]. Here, we are interested in techniques which give a more direct access to the real structure of the mesoporous host and to the dynamics on a single-molecule basis, and thus reveal structural and dynamic features which are not obscured by ensemble or statistical averaging as in conventional techniques. 

The availability of pulsed field gradient (PEG) techniques has had the most significant impact in terms of making it possible to perform 2D- and 3D-NMR experiments on polymer samples. These methods have taken the place of traditional radiofrequency phase cycling methods for coherence selection. By optimizing the use of the spectrometer s dynamic range, PEG techniques not only save time but also drastically reduce artifact noise. 

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