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Dr. John Badger jb at MSI.COM
Mon Nov 17 18:38:30 EST 1997

Yes the calculation of F000 must include all atoms in the
 crystal cell whether you see them or not.

 For disordered solvent the simplest method is to calculate
 the volume outside the known structure and then use the expected
 solvent density for the crystal mother liquor (i.e. it would
 be about 0.334e/A**3 if you had pure water, usually more
 for most crystals since you may some salts etc).

 Also, don't forget about the hydrogens on the protein,
 which probably aren't in your model either.

 Another slightly tricky point in accurate calculations is that
 real-space models of the protein density tend to be a little
 low on electron count since you lose the electron density
 in the Gaussian tail outside the atomic radius when you
 set-up the model.

 John Badger

 Product Development Manager, Macromolecular Crystallography
 Molecular Simulations Inc

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