Manual

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.

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Last modified on September 3, 2009.