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- Title
Peptide conformations. Part 30. Assignment of the <sup>1</sup>H-, <sup>13</sup>C-, and <sup>15</sup>N-NMR spectra of cyclosporin A in CDCl<sub>3</sub> and C<sub>6</sub>D<sub>6</sub> by a combination of homo- and heteronuclear two-dimensional techniques.
- Authors
Kessler, Horst; Loosli, Hans-Rudolf; Oschkinat, Hartmut
- Abstract
The 1H-, 13C-, and 15N-NMR spectra of the immunosuppressive cyclic undecapeptide cyclosporin A ( 1) have been analyzed at 300 MHz in CDCl3, C6D6, and mixtures of these solvents. A combination of different homo- and heteronuclear two-dimensional NMR techniques enable complete assignment of all H-, C- and 4 N-signals. Recognition of the proton spin systems has been achieved via 1H,1H-COSY and double-quantum-1H-NMR spectroscopy. NOESY spectra yield some sequence assignments, but two techniques using coupling across amide bonds have been applied to get independent assignments of all amino acids in the sequence: ( i) An 1H,1H-COSY spectrum optimized for small coupling constants enables the detection of long-range couplings from N-methyl groups to both α-protons attached to that amide bond. ( ii) An 1H, 13C-COSY spectrum optimized for C,H-long-range couplings ( J = 5 to 10 Hz) to the eleven CO groups again yields coupling to both α-protons attached to that amide bond. Additionally these two experiments yield the assignment of N-methyl protons and carbonyl C-atoms. Normal and relayed 1H,13C-COSY in both solvents have been applied to assign all C-atoms via their directly attached and remote protons. An 1H,13C-COLOC spectrum at 500 MHz in CDCl3, which uses H,C-long-range couplings confirms the assignment of all proton spin systems as well as the C-signals of each individual amino acid. Ambiguities in the assignment of the C(δ)'s of MeLeu have thus been removed. An 1H,15N-COSY spectrum enables the assignment of the 4 NH N-atoms.
- Publication
Helvetica Chimica Acta, 1985, Vol 68, Issue 3, p661
- ISSN
0018-019X
- Publication type
Article
- DOI
10.1002/hlca.19850680318