NMR investigations on alanyl-[15% 13C, 95% 15N]-proline: 15N chemical shifts and 13C15N coupling constants

The dipeptide alanylproline has been prepared with the proline residue both 13C (15%) and 15N (95%) enriched. 15N NMR spectra of alanylproline reveal signals for both possible conformations—cis and trans—of the dipeptide backbone in solution. Different pK values for both conformers are obtained from the pH dependence of the 15N chemical shifts using a least square programme based on the Henderson–Hasselbach equation. These different values are discussed in terms of interaction between the α-amino group and the carboxylate group and between the carboxylate oxygen and the carbonyl oxygen of the dipeptide via hydrogen bonding. Further evidence for these interactions is obtained from the pH dependence of the ratio of the 15N NMR signal intensities of the two conformers. One, two or three bonded 13C15N coupling constants measured in the 13C NMR high resolution spectra have different values in the cis and trans isomers of alanylproline and thus indicate different geometry in the pyrrolidine ring.

[1]  K. Wüthrich,et al.  The X‐Pro peptide bond as an nmr probe for conformational studies of flexible linear peptides , 1976, Biopolymers.

[2]  H. Rüterjans,et al.  15N nuclear magnetic resonance investigations on amino acids. , 1976, Proceedings of the National Academy of Sciences of the United States of America.

[3]  R. Lichter,et al.  Letter: Organic structure characterization by natural-abundance nitrogen-15 nuclear magnetic resonance spectroscopy. Penicillin and cephalosporin derivatives. , 1976, Journal of Organic Chemistry.

[4]  Z. Malik,et al.  The 15N nuclear magnetic resonance of Friend leukemic cell (gly-15N) hemoblogin. The resolution of noncovalent bonding interactions. , 1976, Journal of the American Chemical Society.

[5]  R. B. Moon,et al.  Applications of natural-abundance nitrogen-15 nuclear magnetic resonance to large biochemically important molecules. , 1975, Proceedings of the National Academy of Sciences of the United States of America.

[6]  G. Hawkes,et al.  Theory and practice for studies of peptides by 15N nuclear magnetic resonance at natural abundance: gramicidin S , 1975, Nature.

[7]  P. Fromageot,et al.  13C-nuclear magnetic resonance studies of 85% 13C-enriched amino acids and small peptides. pH effects on the chemical shifts, coupling constants, kinetics of cis-trans isomerisation and conformation aspects. , 1975, Biochimica et biophysica acta.

[8]  D. Rabenstein,et al.  Nuclear magnetic resonance studies of the acid-base chemistry of amino acids and peptides. II. Dependence of the acidity of the C-terminal carboxyl group on the conformation of the C-terminal peptide bond. , 1974, Journal of the American Chemical Society.

[9]  P. Fromageot,et al.  13C nuclear magnetic resonance studies of 85 percent 13C-enriched amino acids. Chemical shifts, coupling constants Jc-c, and conformation. , 1974, Journal of the American Chemical Society.

[10]  J. Schellman,et al.  Location of proline derivatives in conformational space. I. Conformational calculations; optical activity and NMR experiments , 1970, Biopolymers.

[11]  John D. Roberts,et al.  NITROGEN-15 MAGNETIC RESONANCE SPECTROSCOPY. II. COUPLING CONSTANTS. , 1964 .

[12]  B Pullman,et al.  Molecular orbital calculations on the conformation of amino acid residues of proteins. , 1974, Advances in protein chemistry.