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Mobility-ordered spectroscopy

The method has been given the name DOSY for diffusion-ordered spectroscopy. It is related to mobility-ordered spectroscopy (MOSY) for analysis of electrophoretic mobilities [Heil, Holl, Joh2, Mor4]. By using shielded gradients with amplitudes larger than... [Pg.192]

The study of molecular diffusion in solution by NMR methods offers insights into a range of physical molecular properties. Different mobility rates or diffusion coefficients may also be the basis for the separation of the spectra of mixtures of small molecules in solution, this procedure being referred to as diffusion-ordered spectroscopy (DOSY) [271] (Figure 5.11). In this 2D experiment, the acquired FID is transformed with respect to 2 (the acquisition time). [Pg.339]

The presence of surface conductance behind the slip plane alters the relationships between the various electrokinetic phenomena [83, 84] further complications arise in solvent mixtures [85]. Surface conductance can have a profound effect on the streaming current and electrophoretic mobility of polymer latices [86, 87]. In order to obtain an accurate interpretation of the electrostatic properties of a suspension, one must perform more than one type of electrokinetic experiment. One novel approach is to measure electrophoretic mobility and dielectric spectroscopy in a single instrument [88]. [Pg.189]

An advantage of NMR spectroscopy is the analysis of protein dynamics. Measurement and analysis of the relaxation parameters R1 R2, and the 15N NOE of 15N-labeled proteins leads to an order parameter (S2) that can describe the relative mobility of the backbone of the protein. Both collagenase-1 and stromelysin-1 have been studied either as inhibited complexes or the free protein [19, 52], Stromleysin-1 was studied with inhibitors binding to prime or nonprime subsites. Presence or absence of inhibitors in the nonprime sites had minor effects on the highly ordered structure of residues in these subsites, which are in contact with the... [Pg.87]

Phospholipids, which are one of the main structural components of the membrane, are present primarily as bilayers, as shown by molecular spectroscopy, electron microscopy and membrane transport studies (see Section 6.4.4). Phospholipid mobility in the membrane is limited. Rotational and vibrational motion is very rapid (the amplitude of the vibration of the alkyl chains increases with increasing distance from the polar head). Lateral diffusion is also fast (in the direction parallel to the membrane surface). In contrast, transport of the phospholipid from one side of the membrane to the other (flip-flop) is very slow. These properties are typical for the liquid-crystal type of membranes, characterized chiefly by ordering along a single coordinate. When decreasing the temperature (passing the transition or Kraft point, characteristic for various phospholipids), the liquid-crystalline bilayer is converted into the crystalline (gel) structure, where movement in the plane is impossible. [Pg.449]

Srinivasan, G, Kyrlidis, A., McNeff, C., and Muller, K., Investigation on conformational order and mobility of diamondbond-C18 and Cl 8-alkyl modified silica gels by Fourier transform infrared and solid-state NMR spectroscopy, J. Chromatogr. A, 1081, 132, 2005. [Pg.298]

These include, again in the approximate order of decreasing usefulness, (a) optical spectroscopy, (b) density measurements, (c) NMR (Knight shifts), (d) conductivity measurements (mobilities and temperature coefficients), (e) ESR, and (f) thermochemistry. There is every reason to believe that in the future other techniques will be applied to these studies, and that a number of subtle features of the solutions will be uncovered. [Pg.34]

From (6.44), we see that in order to obtain a selective membrane, the value of the ion-exchange constant must be small and the sodium ion mobility in the hydrated layer relative to that of the hydrogen ion must also be small. The expansion of the selectivity coefficient to include selectivity to other ions involves inclusion of more complex ion-exchange equilibria, and the use of a more complex form of the Nernst-Planck equation. This rapidly leads to intractable algebra that requires numerical solution (Franceschetti et al 1991 Kucza et al 2006). Nevertheless, the concept of the physical origin of the selectivity coefficient remains the same. Electrochemical impedance spectroscopy has been successfully used in analysis of the ISE function (Gabrielli et al 2004). [Pg.143]

For the investigation of the molecular dynamics in polymers, deuteron solid-state nuclear magnetic resonance (2D-NMR) spectroscopy has been shown to be a powerful method [1]. In the field of viscoelastic polymers, segmental dynamics of poly(urethanes) has been studied intensively by 2D-NMR [78, 79]. In addition to ID NMR spectroscopy, 2D NMR exchange spectroscopy was used to extend the time scale of molecular dynamics up to the order of milliseconds or even seconds. In combination with line-shape simulation, this technique allows one to obtain correlation times and correlation-time distributions of the molecular mobility as well as detailed information about the geometry of the motional process [1]. [Pg.548]


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