[phenixbb] question about reflection file tools behavior

[Michael Thompson]

Hello All,

I have a question about the behavior of the reflection file tools within the PHENIX GUI:

I am trying to simply copy a set of FreeRFlags from a higher resolution dataset to a lower resolution dataset. The low-res dataset contains 35264 reflections in the original input mtz. The high-res set contains 43731 reflections. When I use the GUI to write a new mtz using the low-res amplitudes and the high-res FreeRFlags, the result is an mtz with 46323 reflections. I am confused about why the output has so many reflections, even more than the high res dataset? Also, I noticed that while both input mtz files have a low-res cutoff of 20A, the output mtz has a low-res cutoff around 75A. Can anyone please explain what is going on here? I would like my output file to have the same reflections as the input, and no more. 

I have noticed that the CCP4 program FreeRFlag seems to behave in a similar way, so my guess is that what is happening is a common procedure, but I'm at a loss for an explanation of why this is the case. Also, if there's a better way to implement what I am trying to do I'd be grateful to hear it (perhaps generate entirely new flags for both datasets using the same random seed?).

Thanks for the help!!

Mike





-- 
Michael C. Thompson

Graduate Student

Biochemistry & Molecular Biology Division

Department of Chemistry & Biochemistry

University of California, Los Angeles

miket at chem.ucla.edu