13C CPMAS

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. 

Figure 4 Expected SRI plots for 13C CPMAS (top) and DDMAS (bottom) NMR peak intensities (solid lines) against fluctuation frequency (Hz). The fluctuation frequencies were divided into the following three regions, static (/a or /b), slow (//a or //b), and high frequency (///a or ///b) regions. The maximum intensities are given by S. In the presence of slow fluctuation motions, the peak intensities can be modified as the dotted lines (//a or //b ). In the nearly static region, the peak intensities could be changed into the dotted lines /a or /b, depending upon efficiency of cross-polarization or Tn values. From Ref. 29.

The frequency scale detected by 13C-resolved H spin-lattice relaxation time in the rotating frame Tq) 1 evaluated from the 13C CPMAS spectra42 is similar to that of the 13C T2C values and line-shape analysis16 for 13C (or 15N) or 2H nuclei, as illustrated in Figure 3. It is demonstrated... 

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 27 13C CPMAS (left) and DDMAS (right) of [l-13C]Ala-labelled bR from PM recorded at various temperatures between —10 and 40 °C. From Ref. 179 with permission.

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 40 13C CPMAS (left) and DDMAS (right) NMR spectra of [3-13C]Ala-ppR alone (a and b) and truncated ppR (1-220) (c and d) reconstituted in egg PC bilayer, respectively. 13C NMR signals from the C-terminal region in ppR are shown in the grey (a and b) and arrows (c and d). The resonance peak at 14.1 ppm is ascribed to the methyl carbon peak of egg PC as shown by the asterisk. From Ref. 215 with permission.

Using the OPENCORE NMR spectrometer, standard solid-state NMR experiments have been demonstrated in Ref. 2. They include 1H-13C CPMAS with TPPM decoupling, 13C-15N dipolar recoupling under MAS, 1H FSLG, 13C-13C 2D exchange, and so on. Here we show two more examples, where the spectrometer was used to implement standard pulse sequences, but in somewhat demanding circumstances in terms of sensitivity. 

In the list of diazoketones studied by us95 mostly derivatives were included which have in solution no or only a small tendency for a Wolff rearrangement. Nevertheless we found not a single diazoketone 71 which enabled us to identify a ketocarbene 72, only the corresponding ketenes 73 could be detected. The same observation was made when we studied in collaboration with Yannoni et al." the photochemically induced deazotation of l-diazo-2-propanone in an organic matrix at 77 K, using 13C CPMAS NMR spectroscopy as the analytical tool. 

Fig. 10.24. 13C CPMAS SSNMR spectrum of drug formulation (bottom) together with the spectrum of the solvated form A of the API (second from the bottom), formulation excipients (second from the top) and the solvated form B of API (top).

A, which is shown in the second spectrum from the bottom in Fig. 10.24. Comparing the carbon spectrum of Form A to that of a different crystalline form, Form B, shown in the topmost spectrum of Fig. 10.24, reveals several notable differences in both chemical shifts and line shapes. This, in fact, is often the case for different polymorphs of the same chemical entity, and it enables a clear distinction between the various crystalline forms when present in a mixture. A 13C CPMAS spectrum of a standard sample of the excipients, in the appropriate proportions for the formulation, was also acquired for reference. This is shown as the second spectrum from the top in Fig. 10.24. 

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...

The study of HS extracted from both fractions (pellets and matrices) was performed by various geochemical analyses CHONS elemental analysis, Fourier-transformed infrared spectroscopy (FTIR) and solid-state 13C CPMAS NMR. 

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