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Comparison of Maximum Quantum Filtered NMR Spectroscopy (MAXY NMR) and Other Two‐Dimensional NMR Approaches for Resonance Assignment of Peptides
Author(s) -
Liu Maili,
Nicholson Jeremy K.,
Lindon John C.,
Sanderson Paul N.,
Tranter George E.
Publication year - 1996
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/(sici)1097-458x(199611)34:11<865::aid-omr981>3.0.co;2-e
Subject(s) - chemistry , carbon 13 nmr satellite , nuclear magnetic resonance spectroscopy , conformational isomerism , nuclear magnetic resonance spectroscopy of nucleic acids , spectroscopy , nmr spectra database , proton nmr , transverse relaxation optimized spectroscopy , resonance (particle physics) , chemical shift , methylene , two dimensional nuclear magnetic resonance spectroscopy , pulse sequence , nuclear magnetic resonance crystallography , fluorine 19 nmr , amide , deuterium nmr , spectral line , nuclear magnetic resonance , stereochemistry , molecule , organic chemistry , physics , quantum mechanics , particle physics , astronomy
The 1 H and 13 C NMR spectra of the tridecapeptide neurotensin were assigned in trifluoroethanol solution with the help of two‐dimensional 1 H‐detected maximum quantum filtered NMR spectroscopy (MAXY NMR), which allows the separate detection of CH, CH 2 and CH 3 1 H NMR resonances. In particular, the selective detection of CH protons from leucine and isoleucine residues, normally obscured by CH 2 resonances, was facilitated by the use of the MAXY–TOCSY experiment, as was the identification of individual methylene protons in amino acids with overlapping methylene resonances. The approach is compared with the use of conventional TOCSY spectroscopy. A new pulse sequence, gem ‐TOCSY, is demonstrated and its relative usefulness is also discussed in the context of peptide resonance assignment. The NMR results demonstrated conformational interchange, which was slow on the NMR time‐scale, between cis and trans conformers of proline‐10. Conformation‐dependent data, including coupling constants, amide proton chemical shift temperature coefficients, NOEs obtained from a ROESY experiment and circular dichroism spectra indicated that neurotensin in trifluoroethanol solution is flexible with no single fixed conformation predominating. Nevertheless, this work demonstrates clearly the potential for the general application of the MAXY NMR approach to the assignment of highly overlapped resonances in 1 H NMR spectra of peptides and proteins.