SOMO - Add/Edit SAXS Atomic Coefficients Lookup Table Module:
In this module, you can edit the atomic SAXS coefficients table. For each atom, the scattering
factor is approximate by a sum of four exponentials requiring eight coefficients and
a constant. The values in the somo.saxs_atoms are taken from the International Tables of
Crystallography, but can be edited at will.
A pull-down list of the entries currently present in the table can be accessed in the first field,
Number of SAXS Entries in this file.
New entries can be added by writing an identifier in the following field, SAXS Atom Identifier:.
This identifier will be carried over to the somo.hybrid and somo.atom tables,
linking their entries to the SAXS atomic coefficients in this table.
The coefficients are the pre-exponential factors a(i) and the exponentials b(i),
plus the constant c.
The last field in this panel, Atomic Volume (A^3):, is the atomic excluded volume
used to correct the scattering function, although that of the atomic groups (i.e., with the H atoms
bound) seem to be more appropriate (see Svergun et al., J. App. Cryst. 28:768-773, 1995). Indeed,
the atomic group excluded volumes can be entered in the somo.atom table (see
here), bypassing the somo.saxs_atoms value. For other atoms,
we have used values calculated from the atomic radii reported in the
where references to the original sources are also listed.
www contact: Emre Brookes
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Last modified on April 30, 2012.