NMR conformational studies

Carbon-13 and Proton NMR Conformational Studies of Nitrogen Heterocycles H. Booth, Kem.-Kemi, 1980, 7, 5-10. 

Lipid bilayers have been studied in vesicles of about 500 A diameter. The bilayers can be made of many lipids. The most common lipid is lecithin, phosphatidyl choline (PC). Packing the lipids in the vesicle results in two-thirds of the lipid head groups on the external face about one-third on the internal face. The head group of the lipid PC is phosphocholine -O-POJ-O-CH2-CH2N (013)3 and the head group is studied by P, H, D or C NMR and the long fatty chains by C, H, or D NMR. Conformational studies of the molecules by conventional de-coupling, nuclear Overhauser effects and by Ln(III) probes... 

One test of this proposed two-step charge recombination is provided by triad 8. In this molecule, the quinone moiety has been moved from the 5,15 relationship to the carotenoid as in 4 to the 5,10 relationship. Thus, the carotenoid and quinone species have been brought much closer together. This has been demonstrated by the NMR conformational studies of both molecules [27], If recombination of C -P-Q were to occur by a direct electron transfer as per step 5 in Figure 9, this change should lead to a large increase in the recombination rate. However, as seen in Table 2, triads 4 and 8 have identical charge separation lifetimes, within experimental error, as would be expected from the two-step mechanism. 

Many compounds containing a donor and an acceptor joined by a flexible linker have been synthesized (see Ref. 185 for an extensive list of references). The difficulty in using such compounds to study the distance dependence of ET is that the flexibility of the tinker precludes knowing the donor-acceptor separation precisely. Distances have been estimated from fluorescence quenching volumes (61) and NMR conformational studies (60) with such compounds. NMR studies indicated that the methylene tinker between the porphyrin and the quinone in carotenoid-porphyrin-quinone triads is in an extended (all-anti) conformation (60). The calculated value of p, based on this conformation for the series of methylene linkers, was... 

Munro SLA, Craik DJ. NMR conformational studies of fenamate non-steroidal antiinflammatory drugs. Magn Reson Chem 1994 32(6) 335-342. 

Ballio, A., S. Castellano, S. Cerrini, A. Evidente, G. Ran-DAzzo, and A. L. Segre, H-NMR conformational study of fiisi-coccin and related compounds Molecular conformation and biological activity. Phytochemistry, 30, 1137-146 (1991). 

Several NMR conformational studies were based on the determination of /( H- H) values and the application of Karplus equations, and are well... 

In the NMR conformational study of folded polypeptides, in addition to the well established NMR techniques for small peptides (2-4) one may also rely on the NMR parameters of the polypeptide side chain signals for detection of local conformational transition, intramolecular interactions and chemical modification effects, resulting not only from neighbouring amino acid residues, but also from residues which, while remote in the primary structure, become close to one another by the folding of the polypeptide backbone(5). 

Garbay-Jaureguiberry, C., B.P. Roques, L. Delcambe, F. Peypoux, and G. Michel NMR Conformational Study of Iturin A, an Antibiotic from Bacillus subtilis. FEBS-Letters 93, 151 (1978). 

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