Oxygen-17 Nuclear Magnetic Resonance Spectroscopy:
a new tool for studying biological macromolecules
Our entire nervous system is dependent upon the proper function of ion channels,
pores in cell membranes that are able to transport ions, such as potassium and sodium,
in and out of the cell. High magnetic field nuclear magnetic resonance (NMR)
using oxygen-17 (17O), an isotope of oxygen with one extra neutron in its nucleus,
has been developed to reveal precisely how these ion channels attract and transport ions
without binding them too tightly to the macromolecule that forms the ion channel.
Ion transport through membranes (see schematic above) governs nerve conduction and many other biological processes.
Because 17O is a quadrupolar nucleus, it is a very sensitive indicator of the electric fields of nearby ions.
By substituting 17O on one oxygen site of
the macromolecule that forms an ion channel,
a single step in the ion transport process can
be probed. At magnetic field strengths below
the 21.1 teslas provided by the new 900MHz
NMR magnet at the National High Magnetic
Field Laboratory (right), the signals from
the 17O atoms (left) are too broad to be
sufficiently sensitive to detect the presence
of ions passing through the ion channel.
Hu et al., Journal of the
The shift in the 17O
NMR signal upon detecting American Chemical Society
the electric field from a nearby potassium ion (K+). (in press - 2005)