CPMAS NMR

Lyerla J R, Yannoni C S and Fyfe C A 1982 Chemioal applioations of variable-temperature CPMAS NMR speotrosoopy in solids Accounts Chem. Res. 15 208-16... 

Although not a heteroaromatic compound, the case of citrinin studied by Destro and Luz ([97JPC(A)5097] and references therein) is so significant that it deserves mention here. Citrinin exists in the crystal as a mixture of the p-quinone 5a and o-quinone 5b tautomers (Scheme 3). The equilibrium ii temperature dependent and by using CPMAS NMR (Section VI,F) and, more remarkably. X-ray crystallography, the authors were able to determine the AH and AS values (the rate is extremely fast on the NMR time scale, >10 s ). 

Some reviews relevant for this section concern N CPMAS [86AG(E)383] of pyrazoles, including CPMAS results (93MRC107) and proton transfer in solid heterocycles (94JHC695). The most relevant studies reported in Table X are (1) the use of C CPMAS NMR to identify... 

Different solid-state NMR techniques CPMAS NMR, the second moment of the signal, the spin-lattice relaxation time in the rotating frame T p) were combined to reach the conclusion that in the case of por-phine H2P the double-proton transfer is followed by a 90° rotation within the crystal (see Scheme 2). 

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 34 Left (a) equilibrium storage modulus G as a function of y-irradiation dose determined from DMA experiments on exposed PU samples (b) 1/T2ave as a function of G. Right BC CPMAS NMR measurements on non-irradiated PU sample (a) 3 ms, (b) 0.5 ms, and (c) 100 pis. SS denotes soft segment HS denotes hard segment. Reprinted from Maxwell [87], Copyright 2003, with permission from Elsevier.

Figure 11 The SRI plots of the 13C DDMAS NMR spectra of (A) PMEA (containing 7 wt% water), (B) PHEMA gels (containing 40 wt% water), CPMAS NMR spectra of (C) PMEA, and (D) PHEMA gels against temperature. Suppression temperatures Ts at which respective peaks are most reduced are shown by the arrows. From Ref. 29 with permission.

Figure 12, 3C CPMAS NMR spectra for the PVA gels with different polymer concentrations. The polymer concentrations are (A) 9.1, (B) 11.8, (C) 13.8, and (D) 35% (wt/wt%), respectively. From Ref. 100 with permission.

Figure 24 (A) 13C DDMAS and (B) CPMAS NMR spectra of [3-BC]Ala-labelled bR from...

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

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