[phenixbb] refine anomalous
Andreas Förster
docandreas at gmail.com
Mon Sep 8 00:22:33 PDT 2014
Dear all,
I've solved a structure from a SAD dataset collected at 1.54 Å. The
structure contains a good number of sulfurs and also what I think is a
potassium ion.
To verify, I chose a refinement strategy including "Anomalous groups".
This worked well in an important way - R values down by 2 percentage
points - but the refined f' and f" values are way off.
I start out with these parameters in *.eff:
anomalous_scatterers {
group {
selection = (name SD or name SG)
f_prime = 0.319342
f_double_prime = 0.557592
refine = *f_prime *f_double_prime
}
group {
selection = name K
f_prime = 0.365562
f_double_prime = 1.06736
refine = *f_prime *f_double_prime
}
}
What I get back is:
Anomalous scatterer group:
Selection: "(name SD or name SG)"
Number of selected scatterers: 15
f_prime: -1.15797
f_double_prime: 0.00577091
refine: f_prime f_double_prime
Anomalous scatterer group:
Selection: "name K"
Number of selected scatterers: 1
f_prime: -4.41689
f_double_prime: 0.00271946
refine: f_prime f_double_prime
I thought I'd get close to the book values for S and would be able to
identify the other anomalous scatterer by the refined f'/f" values.
Naiveté or stupidity?
Thank you.
Andreas
--
Andreas Förster
Crystallization and X-ray Facility Manager
Centre for Structural Biology
Imperial College London
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