[Protein-crystallography] CNX MR and refinement

Maxwell laobao862 at hotmail.com
Thu Jul 20 10:52:01 EST 2006

Hi, all,
I am trying to determine a structure with Molecular replacement. The
data was collected to 1.7 A in R32 spacegroup with one molecule per
ASU. CNX found a solution and R factor and R-free started in mid 40s
and went to 35 and 43 after simulated annealing (with bulk solvent and
bfactor correction). Anyway, after several rounds of adjustment and
positional and individual B-factor refinement, the R factor is stuck at
27% with R-free of 31%. At this point, I have done anything I could
think of, but could not lower the R factors anymore. I have included
all the water molecules I could find. A look at the output of
positional and b-factor refinement, it seems to me that the R-factors
for the low resolution range is quite high,  R factor is 37% for 4.69 A
to 500 A with R-free of 48% for the same resolution range.
Is this an indication that my MR solution is problematic? Any other
refinement procedures I could use to lower the R-factors some more?
Thanks in advance.
Maxwell Wang, Ph. D.

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