Cross-polarization-magic angle measurements

High-resolution 13C NMR studies have been conducted on intact cuticles from limes, suberized cell walls from potatoes, and insoluble residues that remain after chemical depolymerization treatments of these materials. Identification and quantitation of the major functional moieties in cutin and suberin have been accomplished with cross-polarization magic-angle spinning as well as direct polarization methods. Evidence for polyester crosslinks and details of the interactions among polyester, wax, and cell-wall components have come from a variety of spin-relaxation measurements. Structural models for these protective plant biopolymers have been evaluated in light of the NMR results. 

Solid-state C variable-amplitude cross polarization magic-angle spinning (VACP/MAS) nuclear magnetic resonance (NMR) spectra were acquired for the sorbitol samples. Proton decoupling was achieved by a two-pulse phase modulation (TPPM) sequence. Identical C spectra were measured for the y-form sorbitol samples, and a representative spectrum is shown in Figure 9. 

Correlating positively with the hydrophobicity of the solvent, different fractions of inactivated active centers were measured in different solvents with solid-state NMR spectroscopy (13C-cross-polarization/magic angle spinning (MAS) NMR) (Burke, 1992). Just as with tritiated water (see above), immediate desorption of water molecules from the protein surface was observed after addition to the organic solvent. 

C-cross polarization magic angle spinning (CP-MAS) spectra were obtained on a Bruker CXP-100 instrument. A rotor consisting of a barrel of boron nitride and a base of Kel-F was used. Rotor speed was 3.8 kHz. Recycle time was varied from 0.3 to 1 s. A variety of contact times from 0.5 to 3ms were employed. The Hartmann-Hahn condition was set using a sample of hexamethylbenzene. Chemical shifts were measured with respect to external hexamethylbenzene (by storing the hexamethylbenzene spectrum in another computer memory block) but are quoted with respect to TMS. It is assumed that the chemical shifts of hexamethylbenzene with respect to TMS are the same in solution as in the solid state. 

Cross-polarization/magic-angle spinning and double cross-polarization NMR measurements... 

C NMR spin-lattice relaxations in solid PMMAs of different tacticity were studied by CP/MAS NMR spectroscopy.324-328 The relaxation proceeds more slowly in isotactic PMMA than in syndiotactic PMMA even in the solid state this is because of the faster reorientation of the a-CH3 group in the isotactic chain.135 The nC-T times of the a-methyl carbons of PMMAs with different tacticities were measured over a wide range of temperatures by cross polarization, magic-angle spinning, dipole dephasing (CP/DD)... 

In the second part of this chapter, an illustrative example of PARAFAC analysis for three-way data obtained in an actual laboratory experiment is presented to show how PARAFAC trilinear model can be constructed and analyzed to derive in-depth understanding of the system from the data. Thermal deformation of several types of poly lactic add (PLA) nanocomposites xmdergoing grass-to-rubber transition is probed by cross-polarization magic-angle (CP-MAS) NMR spectroscopy. Namely, sets of temperature-dependent NMR spectra are measured under varying clay content in the PLA nanocomposite samples. While temperature strongly affects molecular dynamics of PLA, the clay content in the samples also influences the molecular mobility. Thus, NMR spectra in this study become a three-way... 

Cross polarization/magic angle spirming (CP/MAS) measurement (19) C NMR, Fourier transform NMR spectrometer at room temperature (1) and at 25 MHz. Internal standard tetramethylsilane and C and 2D-NMR, at 35°C in CDCI3 under a nitrogen (5)... 

From the viewpoint of solid-state NMR, is one among the dilute nuclear spin systems. The cross-polarization-magic angle spinning (CP-MAS) NMR technique is recommended so that the sensitivity of measurement may be increased and the signals narrowed. 

The degradation of EVA and EVA nanocomposites was investigated by solid-state cross-polarization magic angle opening C-NMR spectroscopy Bourbigot et al. described the measurement method in detail. EVA (Escorene UL-00112... 

Four narrow lines are observed in the high-resolution cross-polarization magic-angle spinning 13C NMR spectra of intact, lyophilized samples of Pseudomonas sp. LBr, in addition to the broader lines normally associated with bacterial cellular material. These narrow lines arise from poly-3-hydroxybutyrate. The cellular carbon contained in this storage material can be measured quantitatively and nondestructively from the... 

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