13C CPMAS spectra

From 13C CPMAS spectra, obtained as described in Figure 2 and referenced to external TMS. 

Figure 3.2.14 13C CPMAS spectra of various polymorphs of sulfanilamide. Reproduced with permission from Ref. [33].

Conformational differences can result in variations in local electron density and NMR can be an ideal probe for this type of behavior, via the chemical shielding tensor [31, 32]. For example detailed inter- and intramolecular conformations can be described at high resolution. Proton sites and hydrogen bonds, which are usually averaged in solution state NMR and not easily assessed in crystallographic studies, can be directly determined by solid state NMR. In Fig. 3.2.14 is presented a typical example in which the different polymorphs of sulfanilamide can be distinguished by their 13C CPMAS spectra [33],... 

Solid state 13C CPMAS NMR spectra of Wheat High Molecular Weight (W.HMW) subunits show well resolved resonances identical with spectra of dry protein and peptide samples [24], Most of the amino acids side-chain resonances are found in the 0-35 ppm region followed by the alpha resonances of the most abundant amino acids glycine, glutamine and proline at chemical shifts of 42, 52 and 60 ppm, respectively, and the carbonyl carbons show a broad peak in 172-177 ppm region. The CPMAS spectra of hydrated whole HMW provides important information on the structural characteristics. 

In the solid, dynamics occurring within the kHz frequency scale can be examined by line-shape analysis of 2H or 13C (or 15N) NMR spectra by respective quadrupolar and CSA interactions, isotropic peaks16,59-62 or dipolar couplings based on dipolar chemical shift correlation experiments.63-65 In the former, tyrosine or phenylalanine dynamics of Leu-enkephalin are examined at frequencies of 103-104 Hz by 2H NMR of deuterated samples and at 1.3 x 102 Hz by 13C CPMAS, respectively.60-62 In the latter, dipolar interactions between the 1H-1H and 1H-13C (or 3H-15N) pairs are determined by a 2D-MAS SLF technique such as wide-line separation (WISE)63 and dipolar chemical shift separation (DIP-SHIFT)64,65 or Lee-Goldburg CP (LGCP) NMR,66 respectively. In the WISE experiment, the XH wide-line spectrum of the blend polymers consists of a rather featureless superposition of components with different dipolar widths which can be separated in the second frequency dimension and related to structural units according to their 13C chemical shifts.63... 

Figure 26 13C CPMAS (A) and DDMAS (B) NMR spectra of [l- 3C]Val-labelled bR from PM. From Ref. 19. The assigned peaks is based on the data of site-directed mutagenesis 85- 87 and REDOR filter experiment.188...

Figure 31 100.6 MHz 13C CPMAS NMR spectra of [l-13C]Val-labelled D85N mutant at...

Figure 35 13C CPMAS NMR spectra of [l- 3C]Val- and [3- 3C]Ala-labelled bR reconstituted in DMPC bilayer (1 50 mole ratio) at various temperatures from 40 (A) to —10 °C (D). The methylene peak-position of the fatty acyl chain of the lipid at 32 and 30 ppm is a good indicator of the gel and liquid-crystalline phase, respectively. From Ref. 206 with...

Figure 37 13C CPMAS (left) and DDMAS (right) NMR spectra of [3-BC]Ala-labelled ppR (a), (b) in egg PC bilayer as compared with those of [3-13C]Ala-labelled bR (c), (d) from PM. From Ref. 212 with permission.

Figure 44 13C CPMAS (left) and DDMAS (right) NMR spectra of uncomplexed [3- 3C]Ala-...

Figure 2.45 X-ray powder diffraction patterns of sPP samples in (a) form I and (b) form II and (c,d) corresponding solid-state 13C NMR CPMAS spectra.

The cyclopentyl cation (39) undergoes a rapid degenerate rearrangement which can be frozen out at cryogenic temperatures as shown by solid state CPMAS 13C NMR spectra.57 MP2/6-31G(d,p) calculations show that cyclopentyl cation has a twisted conformation 4058 in which the axial hydrogens are bend toward the carbocation center. This is due to the pronounced geometrical distortion caused by the hyper-conjugative interaction of the /i-cr-C-H-bond with the formally vacant 2pz-orbital at the C+ carbon of this secondary carbocation. 

Fig. 10.25. 13C CPMAS and 19F MAS SSNMR spectra of the drug formulation (top) and the physical mixture of API with excipients (bottom). Shown above each peak are the relaxation times calculated from the 13C detected...

Chemical shifts of 13C CPMAS NMR spectra of 4-(4-fluorophenyl)-2- 4-[4-(3-trifluoromethylphenyl)piperazino]butyl -2,3-dihydro-lH-pyrido [l,2-c]pyrimidinel,3-dione and its hydrochloride salt were unambiguously assigned by theoretical calculations at GIAO/DFT (B3LYP/6-311 +G ) level (08JST325). Absolute energies, bond angles, and bond distances of 9,10-dimethoxy-l, 6,7,11 fc-tetrahydro-2H,4H-[l, 3]oxazino[4,3-fl]... 

Claramunt et al. [23] recorded the 13C and 15N CPMAS spectra of solid sample of omeprazole and all signals assigned. The sample consists uniquely of the 6-methoxy tautomer. 

Polymerization of pyrogallol (measurement of optical density) ring cleavage of pyrogallol and catechol (measurement of C02 release) yields of humic polymers IR and 13C CPMAS NMR spectra resembling natural HAs... 

Birnessite (8-Mn02) Condensation of glucose and glycine under soil ambient conditions (measurement of optical density) yields of humic substances XANES study of change in speciation of Mn ESR study of Mn speciation in solution 13C CPMAS NMR spectra of FA fraction resembling spectra of natural FAs Jokic et al. (2001b)... 

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