Spin-lattice relaxation rotating frame

Jonas et al. measured the proton rotating frame spin-lattice relaxation time (Tip) at pressures from 1 bar to 5000 bar and at temperatures of 50 to 70 °C for DPPC and at 5 to 35 °C for POPC. If intermolecular dipolar interactions modulated by translational motion contribute significantly to the proton relaxation, the rotating frame spin-lattice relaxation rate (1/Tip) is a function of the square root of the spin-locking field angular frequency... 

The precipitates of PVPh/PDMA from methanol and acetone solutions were examined by CPMAS NMR [51], and evidence for specific interaction was obtained with a 3 ppm shift in the phenolic carbon resonance peak. The proton spin-lattice relaxation times Tj were shorter than those predicted by a linear model, though the rotating frame spin-lattice relaxation times Tjp of the com-... 

Tip (13C), the rotating frame spin-lattice relaxation time can partially be correlated with dynamic mechanical data. It has been shown to characterise qualitatively the... 

Tp, absolute rotating frame temperature T], spin-lattice (longitudinal) relaxation time of a nucleus Tip, rotating-frame spin-lattice relaxation time T 2, spin-spin (transverse) relaxation time of a nucleus T-Zp, rotating-frame spin-spin relaxation time T2, effective spin-spin (transverse) relaxation time of a. nucleus... 

Yoshioka, S. Aso, Y. Kojima, S. Different molecular motions in lyophilized protein formulations as determined by laboratory and rotating frame spin-lattice relaxation times. J. Pharm. Sci. 2002, 91 (10), 2203-2210. 

Thallium. 3H NMR spectra of laser-irradiated T1H3P04 gave values for NMR rotating frame spin-lattice relaxation times as a function of temperature.425 203,205T1 NMR data for the ternary semiconductor TlTaS3 were consistent with a chain structure.426... 

The rotating-frame spin-lattice relaxation time for protons, Tip,( H), was measured indirectly from CPMAS/DD NMR to probe possible molecular scales of heterogeneity in the miscible poly(benzyl methacrylate)/poly(ethylene oxide) blend over the whole composition range. ... 

IV.C.l. ROTATING FRAME SPIN-LATTICE RELAXATION MEASUREMENTS... 

The NMR rotating frame spin-lattice relaxation time (Tjp) method, which has been used successfully in our laboratory in studies of pressure effects on diffusion in highly viscous liquids, was used in this study to measure lateral diffusion of the phospholipid molecules in DPPC and POPC vesicles. An advantage of this method is that the diffusion coefficient is found directly from measured quantities without estimations of molecular parameters or the effects of the addition of spin or fluorescence probes to... 

Figure 34.3 shows the results of a variable contact time CP experiment, in which the Si CP contact period (tcp) is varied in order to elucidate the Si CP (relaxation) time constant (ThsO for each Si peak. The early (small tcp) part of such curves is typically dominated by the rate of CP transfer, as characterized by the rate constant and the latter part of such curves is usually determined by the rate constant of the rotating frame spin-lattice relaxation of the protons responsible for polarization transfer to the observed silicons, as characterized by the time constant, (assuming > Thsi). These curves can be analyzed mathematically in terms of well-known equations [17]. 

B. Molecular Mobility as Determined by the Laboratory and Rotating Frame Spin-Lattice Relaxation Times of Protons... 

Figure 8 shows the time course of the laboratory and rotating frame spin-lattice relaxation of protons in lyophilized y-globulin formulations containing dextran, determined at 55°C using a pulsed NMR spectrometer [26]. 

Han et al. studied the dynamics of hydrated water molecules in NAFION by means of high-resolution MAS NMR measurements. Bound and free states of hydrated water clusters as well as the exchange protons were identified from the NMR chemical shift measurements, and their activation energies were obtained from the temperature-dependent laboratory- and rotating-frame spin-lattice relaxation measurements. Besides, a pecufiar motional transition in the ultralow frequency region was observed at 373 K for the free hydrated water from the rotating-frame NMR spin-lattice relaxation time measurements [60]. 

NMR rotating-frame spin—lattice relaxation time measurements revealed in a sensitive manner the evolution of the microscopic environment and proton dynamics of the two distinct hydrogen bond types in the system, compatible with the electrical conductivity and the impedance spectroscopy measurements. In addition, the reorientational motion of the PO4 tetrahe-dra, as revealed by rotating-frame NMR, is coupled to the proton dynamics [118]. 

Xiong, 1., and Maciel, G.E. Variable-temperature high-resolution proton NMR study of laboratory-frame and rotating-frame spin-lattice relaxation in coals. 1997 11 866-878. 

Off-Resonance Rotating Frame Spin-Lattice Relaxation Theory, and in Vivo MRS and MRI Applications... 

In contrast to nematics, a helical twist of the molecular director takes place in the chiral nematic phase. Studies of the spin-lattice relaxation in chiral nematics have shown that the relaxation mechanisms are essentially the same as in pure nematics [141, 142]. At high Larmor frequencies the relaxation is diminished by molecular self-diffusion and by local molecular rotations, whereas director fluctuations determine the relaxation rate at low Larmor frequencies. This can be easily understood because the spin-lattice relaxation rate in the MHz region is dominated by orientational fluctuations with wavelength much smaller than the period of the helix. The influence upon the rotating frame spin-lattice relaxation time Tip of the rotation of the molecules due to diffusion along the helix, an effect specific for twisted structures, has not been observed in COC [143]. 

Figures 28, 29, 30, 31, 32, 33, and 34 show a series of typical spin-lattice relaxation dispersion curves. The technique has been applied to melts, solutions, and networks of numerous polymer species. As experimental parameters, the temperature, the molecular weight, the concentration, and the cross-link density were varied. For control and comparison, the studies are partly supplemented by rotating-frame spin-lattice relaxation data and, of course, by high-field data of the ordinary spin-lattice relaxation time. Furthermore, the deuteron spin-lattice relaxation was employed for identifying the role different spin interactions are playing for relaxation dispersion.

Although other relaxation mechanisms may be important for some nuclei, the dipolar relaxation mechanism of P that is coupled to protons and the chemical-shift anisotropy mechanism are most important for nucleic acids. In the case of dipolar relaxation, expressions for the spin-lattice relaxation time T, spin - spin relaxation time Tj, nuclear Overhauser effect (NOE), rotating frame spin-lattice relaxation time in an off-resonance radiofrequency (rf) field T°, and off-resonance intensity ratio R are given by (Doddrell et a/., 1972 Kuhlmann eta/., 1970 James eta/., 1978 James, 1980)... 

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