[phenixbb] low resolution data/parameter ratio
Pavel Afonine
PAfonine at lbl.gov
Fri Aug 14 15:11:54 PDT 2009
Hi Gerwald,
> Two more quick questions:
> how would you identify the best strategy?
I would look at Rfree and Rfree-Rwork, and maps of course. To help in
deciding what are the "good / reasonable" values, use POLYGON (Acta
Cryst. D65, 297-300 (2009)) (phenix.polygon), local real-space
correlation (phenix.real_space_correlation). I think Nat bundled them
all into his magic tool called phenix.validation with will do this and
more (it is GUI based).
> I would aim for the lowest number of parameters with reasonably low
> Rfree?
Yes, this sounds right in general.
> Does phenix report the total number of parameters refined anywhere in
> the log?
It's trivial and not at the same time (at least the way I understand it,
of course I might be very wrong). It's trivial to compute the number of
refinable parameters given the strategy you choose, but how you will
count the restraints which are kind of quasi-observables, and what about
weight that if chosen too strong so it can turn the restraints into
quasi-constraints?
Pavel.
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