th  - 1987 - 51st ENC Conference

Tuesday - AM
Proton-Detected Reteronuclear One- and Two-Dimensional NMR Spectra of
Biomolecules: Shift Correlation and Relaxation Measurements.
William M. Westler and ~ohn L. Markley
Department of Biochemistry
College of Agricultural and Life Sciences
University of Wisconsin-Madison
420 Henry Mall
Madison, Wisconsin 53?06, U.S.A.
Indirect detection of a heteronucleus by scalar coupled protons is a
powerful technique that extends the range of 13C and IsN NMR spectroscopy to
include samples of limited quantity or solubility. Since the relative
sensitivity for detection of NMR active nuclei is proportional to the cube of
the magnetogyric ratio, the maximum sensitivity in a he teronucl ear correlation
experiment can be obtained by detecting the nucleus with the larger
magnetogyric ratio in the coupled spin system. The sample requirement for
proton-detected heteronuclear correlation spectroscopy is at least an order of
magnitude lower than that for conventional heteronuclear experiments. We have
collected one- and two-dimensional proton-detected heteronuclear NMR spectra of
selectively and uniformly ISC and ISN labeled proteins [Anabaena 7120
ferrodoxin (10,000 dalton); Staphylococcus aureus nuclease (17,000 dalton); and
Anabaena 7120 flavodoxin (23,000 dalton)]. Two proteins have been studied at
natural abundance [turkey ovomucoid third domain (6,000 dalton) and summer
squash trypsin inhibitor (3,000 dalton)]. A promising experiment is one that
we call "HOTRAT u (_Hydrogen Observation of Transferred RAre _Tl'S). This method,
which allows one to measure longitudinal relaxation times of rare nuclei in
samples of limited quantity or solubility, is useful in light of the current
interest in the dynamics of biomacromolecules.
[This research was carried out at the National Magnetic Resonance
Facility at Madison (NMRFAM) and was supported by NIH grant RR 02301.]