For POTEntial=3DPO, a restraining function for 3D NOE-NOE
experiments is used.
The intensity of a 3D NOE-NOE crosspeak,
,
between spins i,j, and k, is
proportional to the product of the individual NOE transfer
efficiencies of each mixing time:
where 
is the first and 
the second mixing time,
R the cross-relaxation matrix, 
the
equilibrium magnetization of spins k, and c a constant.
The 3D NOE-NOE intensity can be approximated by
where 
and 
are the distances between spins i, j and j,
k,
respectively, and the proportionality constant is set equal to one.
The 3D NOE-NOE function is given by
where S is the energy constant specified
by the SCALe statement, 
is the
observed NOE-NOE intensities, 
and 
are error bounds, and K is a scale factor specified by
the RSWITch statement. The NOE-NOE connectivity
and the
intensity and error-bound information are provided by
a pair of ASSIgn statements:
The first ASSIgn statement specifies spins i and j, along
with the observed intensity 
and the
error bounds 
and 
. The second ASSIgn
statement specifies spins j and k; the three real numbers
following the second selection are irrelevant and can be set
to arbitrary values.
Note: the 3D NOE-NOE function can be used in combination with
R-6 or center averaging. For further details, the reader is referred to
Habazettl et al. (1992a, 1992b) and Bernstein et al. (1992).
