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					 Oxygen-17 Nuclear Magnetic Resonance Spectroscopy:
   a new tool for studying biological macromolecules
                             K+ ion

                                      Our entire nervous system is dependent upon the proper function of ion channels,
              Ion Channel

                                      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
                                         K+ ion
                                                    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)

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