Hard-to-believe changes in R-free

[Marko Hyvonen]

Dear Yoram,  

As you said, the stereochemical criteria should be used to decide in
the end, so I thought you might have a look at a paper by Nayal et
al.in J Mol Biol 256:228--234 on valence screening of water molecules
in protein  crystals for potential Na+ sites. The authors have a
program called  WASP (WAter Screening Program) which you can ask from  
Enrico Di Cera (enrico at caesar.wustl.edu). 

The program reads a PDB and screens all waters molecules to see if
they would in fact be metal ions. It worked for me nicelly when trying
in distiguish between Na+ or Mg2+. Perhaps this can give you more
support while making the decision.  

cheers, Marko 
      
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 Marko Hyvonen, PhD              tel:  +44-(0)1223-766 030
                                 lab:  +44-(0)1223-766 027
 Department of Biochemistry      fax:  +44-(0)1223-766 082
 University of Cambridge       email:  marko at cryst.bioc.cam.ac.uk 
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