What does the matthews_coeff indicate? You would expect more water than
that, but maybe you have a low Matthews_coeff indicating little solvent?
maybe you have lost the low resolution data which makes it harder to
find water? Maybe you have refined with bulk solvent scaling -
sometimes that also masks the water and you have to look at lower sigma
levels.
Your strong Fo-Fc peak might indicate a rogue bit of data..
Eleanor
Sabini, Elisabetta wrote:
Dear all,
what does it mean when a structure doesn't have many water molecules?
I have a 2.3A data set, 2 molecules in the AU (260 residues each), space
group C2221 - I haven't finished my water search but I don't seem to have
more than 20-30 obvious/good water molecules. The Rfac/Rfree are 22/30%,
the protein is modeled and the ligands are in.
I collected the data at APS SERCAT ID-22. Did I have a dry crystal (!!) or
did the beamline dried it up?!
How many water molecules should I expect at this resolution?
Also, what does it mean when a strong peak in the Fobs-Fc doesn't have the
corresponding 2Fobs-Fc map covering it even at very low sigma?
Thank you!
Eli :o)
PS: I have attached the statistics for the data set from XDS
