[phenixbb] Different stats with different number of macrocycles

Patrick Loll pat.loll at drexel.edu
Wed May 3 14:07:08 PDT 2017

I have an odd observation.

I am finishing a refinement at 2.5 Å, using the Phenix GUI. I performed a three-macrocycle refinement, and saw that the geometry (RMS bonds/angles) and R/Rfree all got better in the first macrocycle, and then worsened in the subsequent two macrocycles.

OK, fine. So I repeated the refinement, except I performed only a single macrocycle (starting from the exact same input coordinates). However, the statistics after this one-macrocycle job did not match the stats seen after 1 macrocycle in the 3-macrocycle job (?!). This doesn’t make sense to me; if you’re starting from the exact same coordinates, shouldn’t the first macrocycle always wind up at the same place, regardless of whether or not the program goes on to do additional macrocycles of refinement?

In case this isn’t clear:

In the 3-macrocycle job, after the first macrocycle, RMS bonds/angles = 0.005 Å/0.9 deg, R/Rfree = 0.208/0.236 (by the end of the third macrocycle, these numbers have changed to 0.009 Å/1.41 deg and 0.212/0.244)

At the end of the 1-macrocycle job, RMS bonds/angles = 0.008 Å/1.4 deg, R/Rfree = 0.209/0.240

This is Phenix version 1.11.1-2575-000.

Any insights welcome.


Patrick J. Loll, Ph. D.  
Professor of Biochemistry & Molecular Biology
Drexel University College of Medicine
Room 10-102 New College Building
245 N. 15th St., Mailstop 497
Philadelphia, PA  19102-1192  USA

(215) 762-7706
pat.loll at drexelmed.edu

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