NMR is a
technique based on the
behavior of
atomic nuclei in
magnetic fields. It is used in
medicine for
magnetic resonance imaging, and in
chemistry/
biochemistry for determining the
structure of chemical compounds.
The basic theory behind NMR is that protons, which spin and have
charge, have a magnetic
dipole (a north and south pole, like miniature
magnets themselves). When protons are subjected to a
magnetic field from a very powerful electromagnet, they reorient in the direction of the magnetic field. The re
orientation causes them to release
radio waves, which can be detected.
For medical applications, this effect is
sufficient, as different
tissues have differing water content, and will return different
signals. However, for more
sophisticated chemical studies, there are several other
effects which take place that allow
structure determinations to be made.
Protons that are very near to each other, or on
adjacent atoms, cause
resonance effects that create
characteristic peaks. With
computer modeling and knowing the sequence of a
protein, it becomes possible to obtain very
clear structures of proteins and other
organic molecules in
solution.