New insights into the bonding arrangements of l-and d-glutamates from solid state< sup> 17 O NMR (original) (raw)
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New insights into the bonding arrangements of l- and d-glutamates from solid state 17O NMR
Chemical Physics Letters, 2003
Magic angle spinning (MAS) from L L -and D D -glutamic acid-HCl at 14.1 T produces highly structured and very similar NMR spectra. Lines from all 4 oxygen sites are readily distinguished and assigned. These 17 O NMR spectra are very different from the previously reported 17 O spectrum of the D D ,L L -form presumably because that was a racemic crystal. 17 O NMR from L L -monosodium glutamate-HCl is very different again requiring the application of double angle rotation and 3 quantum MAS NMR to provide resolution of 5 different sites. Hence high resolution 17 O solid state NMR techniques offer possible new insight into biochemical bonding processes.
Physical chemistry chemical physics : PCCP, 2011
Monosodium L-glutamate monohydrate, a multiple oxygen site (eight) compound, is used to demonstrate that a combination of high-resolution solid-state NMR spectroscopic techniques opens up new possibilities for (17)O as a nuclear probe of biomolecules. Eight oxygen sites have been resolved by double rotation (DOR) and multiple quantum (MQ) NMR experiments, despite the (17)O chemical shifts lying within a narrow shift range of <50 ppm. (17)O DOR NMR not only provides high sensitivity and spectral resolution, but also allows a complete set of the NMR parameters (chemical shift anisotropy and electric-field gradient) to be determined from the DOR spinning-sideband manifold. These (17)O NMR parameters provide an important multi-parameter comparison with the results from the quantum chemical NMR calculations, and enable unambiguous oxygen-site assignment and allow the hydrogen positions to be refined in the crystal lattice. The difference in sensitivity between DOR and MQ NMR experimen...
Solid-state 17O NMR of amino acids
2004
17O solid-state NMR from 14 amino acids is reported here, greatly increasing the number investigated. In most cases well-separated resonances from carbonyl and hydroxyl oxygens with distinct second-order quadrupolar line shapes are observed using a 600 MHz spectrometer with fast magic angle spinning (MAS). This is in contrast to the motionally averaged resonances usually seen from amino acids in solution.
Solid-State NMR and the Crystallization of Aspartic and Glutamic Acids
Crystal Growth & Design, 2016
We used high-resolution solid state 13 C NMR, with cross polarization and magic angle spinning, to study chirality in the crystallization of aspartic acid. We show that, contrary to a recent report, DL-aspartic acid crystallizes over most of its temperature range as racemic crystals rather than a conglomerate of enantiomeric crystals, regardless of whether the solution was prepared by solution of the racemate or by mixing solutions of the pure enantiomers. Over virtually the entire solution temperature range at 1 bar pressure, racemic crystals of aspartic acid are thermodynamically stable, while the conglomerate is metastable. In contrast, in agreement with the literature, glutamic acid crystallizes as a conglomerate under thermodynamic conditions. Solid-state NMR results are confirmed by powder X-ray diffraction.
Polymer Journal, 1993
The side chain motion and structure of the racemic mixture of poly(y-benzyl glutamate) (PBDLG) in the solid state were studied by means of the cross polarization/magic angle spinning (CP/MAS) 13 C NMR. Cµ and CY regions of NMR spectra for PBDLG in the stacked state of phenyl rings exhibit a remarkable difference from those for poly(y-benzyl L-glutamate) (PBLG) with no side chain stacking. Use of y-d2 PBDLG, deuterated at Cy, showed that the upfield shift occurs in a part of y-carbons. It was suggested that this new peak arises from the regular side chain conformation with phenyl ring stacking. The measurements of 13 C T 1µ, spin-lattice relaxation time in the rotating frame, indicated that both the side chain and main chain motions are restricted in the stacked state. However, it is noticeable that such effect of stacking is especially remarkable for C 1 rather than phenyl ring. This means that phenyl rings have a rather high mobility even in the staked state.
3-Methylglutaric acid as a 13C solid-state NMR standard
Solid State Nuclear Magnetic Resonance, 2006
The calibration of a solid-state NMR spectrometer requires setting the magic angle, setting the reference and decoupler frequencies, ensuring that the magnetic field is homogeneous across the sample volume, optimizing the signal-to-noise ratio, determining the p/2 pulse durations, and optimizing the Hartman-Hahn matching condition. Each task has one or more widely accepted standards, such as potassium bromide for setting the magic angle, adamantane for optimizing magnet homogeneity, and hexamethylbenzene or glycine for measuring the signal-to-noise ratio. We show that all of these tasks can be performed using 3-methylglutaric acid (MGA). In the case of high-powered decoupling, the CH 2 and CH carbon peaks of MGA provide an opportunity to evaluate the decoupling in a manner that is superior to any of the commonly used standard compounds. Thus, MGA can be used as a single solid-state NMR standard compound to perform all calibration steps except for magnet shimming.
Polymer Journal, 1990
The molecular motion and structure in poly(y-methyl L-glutamate-coy -stearyl L-glutamate)s with various molar compositions were investigated by means of spin-probe technique and 13 C CP/MAS NMR. By the latter, it was confirmed that a certain part of long alkyl chains forms paraffin-like crystallites as observed in homopolymer of stearyl L-glutamate, and other part exists as the amorphous phase below crystalline melt. An introduction of a small amount of stearyl group considerably raises the mobility of the spin-probe which is embedded in the side chain region surrounding the ix-helical main chain, and further increase of stearyl content does not remarkably alter mobility. It is suggested that spin-probes exist in the amorphous region composed of stearyl groups, and mainly reflect the motional state of this region. the difference of the mobility between methyl L-glutamate side chain and stearyl group are also investigated by the scalar decoupled 13 C NMR spectra in the solid state.
A review of oxygen-17 solid-state NMR of organic materials—towards biological applications
2004
17O solid state NMR of organic materials is developing rapidly. This article provides a snapshot of the current state of development of this field. The NMR techniques and enrichment protocols that are driving this progress are outlined. The 17O parameters derived from solid-state NMR experiments are summarized and the structural sensitivity of the approach to effects such as hydrogen bonding highlighted. The prospects and challenges for 17O solid-state NMR of biomolecules are discussed.