High-resolution 13C nuclear magnetic resonance in solids

Abstract

A procedure is demonstrated for determining the relative contributions of spin-lattice and spinspin interactions to TIp(C), the relaxation time characterizing the loss of spin-locked carbon polarization. This involves the characterization of relaxation processes associated with several cross-polarization experiments. Three glassy polymer Tlp(C) values are shown to be dominated by spin-lattice effects while a crystalline polymer relaxes through a spin-spin mechanism.The combination of cross-polarization,' high-powered heteronuclear decoupling2 and magic-angle spinning3p4 has made it possible to obtain high-resolution, naturalabundance 13C n.m.r. spectra in solid^.^*^ These spectra are sufficiently detailed to

Following Suberization in Potato Wound Periderm by Histochemical and Solid-State 13C Nuclear Magnetic Resonance Methods

“…High-power proton dipolar decoupling [Bl(H) = 65 kHz] was used during data acquisition. Under these conditions, the correct relative intensities are obtained for the peaks observed in each of the spectra (Stejskal et al, 1979;Fukamizo et al, 1986). Additional experimental details are provided in the figure legends.…”

“…As with the histochemical experiments described above, the NMR spectra allow us to monitor changes in chemical structure at key times during suberization (see below). Quantitative comparisons of the I3C peak intensities for these chemically similar samples are expected to provide an accurate assessment of carbon content, since the 2-ms cross-polarization contact time used to acquire the NMR data minimizes intensity variations due to differing rates of proton-carbon cross-polarization and proton spin relaxation (Stejskal et al, 1979;Fukamizo et al, 1986;Stark and Garbow, 1992).…”

“…CPMAS "C NMR spectra (31.9 MHz) of potato tissue after O, 4, 7, and 14 d of wound healing and a protocol of enzymic and chemical treatments that removes 94 to 99% by weight of the unsuberized cell walls and waxes (Pacchiano et al, 1993). All spectra were collected with 2-ms 'H-"C contacts and 1-s recycle delays to ensure that polarization transfer was complete but intensity losses from proton relaxation were comparable for each resonance (Stejskal et al, 1979;Fukamizo et al, 1986). Chemical shifts are quoted with respect to externa1 Asn (side-chain carbonyl = 175.1 ppm).…”

Metabolism of glyphosate in an Arthrobacter sp. GLP‐1

“…The cross-polarization magic-angle spinning (CPMAS) NMR experiments were performed on lyophilized cellular samples ranging in dry weight over 200-300 mg. We were able to detect signals from the uptake of as little as 100 pg 13C. Technical details of the spinning and cross-polarization procedures are reported elsewhere [19,20]. Magic-angle-spinning "N-NMR spectra were obtained at 20.3 MHz using 2-ms cross-polarization transfers from protons and 35-kHz radiofrequency field amplitudes [13].…”

13C Nuclear Magnetic Resonance Study of Suberized Potato Cell Wall

“…A 'H decoupling field of 65 kHz was used throughout (dipolar decoupling). Most spectra were collected with 2-ms contacts, though for chemical composition data, 13C peak intensities were adjusted for variations in rotating-frame proton and proton-carbon relaxation rates by systematically varying the contact time (21). Proton spin-temperature alternation and quadrature phase cycling were used to minimize baseline distortions and other artifacts (1 9, 20).…”