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Nitrogen‐15 n.m.r. studies of 13 C, 15 N labeled arginine
Author(s) -
London R. E.,
Walker T. E.,
Whaley T. W.,
Matwiyoff N. A.
Publication year - 1977
Publication title -
organic magnetic resonance
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0030-4921
DOI - 10.1002/mrc.1270091011
Subject(s) - protonation , chemistry , deprotonation , proton , tautomer , spectral line , nitrogen , resonance (particle physics) , urea , arginine , crystallography , stereochemistry , medicinal chemistry , analytical chemistry (journal) , amino acid , organic chemistry , ion , physics , biochemistry , quantum mechanics , astronomy , particle physics
15 N n.m.r. spectra of [ 13 C‐2, 3‐ 15 N 2 ‐ guanidino ]arginine and [ 13 C, 15 N 2 ] urea were obtained in D 2 O and H 2 O at a variety of pH values both with and without proton decoupling. The effects of the proton exchange rate are readily observable in the proton coupled 15 N spectra. When the guanidino group is deprotonated (p K = 12.5), the terminal nitrogens give a single resonance 6.6 ppm downfield of the protonated species, indicating a rapid tautomeric exchange. The observed NH and CN couplings are compared with calculated values, and good agreement is found for 1 J (CN) using a Blizzard–Santry type calculation. The ramifications of the proton exchange on 15 N n.m.r. spectra of amino acids and peptides are discussed.