th  - 1987 - 51st ENC Conference

WK6
ISOTOPE-FILTERED PROTON NHR EXPERIMENTS
FOR SIMPLIFYING COMPLEX SPECTRA
Stephen W. Fesik* Robert T. Gampe, Jr. Jay R. Luly, Herman H. Stein and
• ' t
Todd Rockway. Pharmaceutical Division, Abbott Laboratories, Abbott Park, IL
60064.
Extracting structural information from proton NHR spectra of large
btomolecules or molecular complexes can be extremely difficult due to the
severe overlap of many signals. Recently, however• experimental approaches
have been introduced to overcome some of these limitations by selectively
detecting protons attached to an isotopically labelled nucleus (1,2) as well
as their scalar (2) or dipolar coupled (3) partners. Isotope-filtered
homonuclear Hartmann-Hahn (HLEV-17) and NOE experiments in which a spin-echo
difference pulse sequence was inserted in the experiment are presented. The
approach is illustrated using an 15N-labelled dipeptide and applied in a study
of the bound conformation of an isotopically labelled pepsin inhibitor. In
addition, isotope-filtered 2D NOE spectra are presented of a large, 15N-
labelled cyclic peptide analog of atrial natriuretic factor incorporated into
a model membrane. From the spectral simplification achieved in the
experiment, additional proton-proton distances were obtained unambiguously,
aiding our structural studies.
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