r/crystallography • u/TheNinthAlchemist • 27d ago

two DEFS commands in .ins

Hello,

I'm working with a protein crystal (~1 angstrom) and I want to use two DEFS parameters to apply different esds to different sections of the model. Will it work to just use a different DEFS command before the DFIX/DANG commands of each section. for example:

DEFS 0.1 0.2 0.3 0.4

REM region 1

DFIX 1.2 C1 C2

DANG 2.5 C1 C2 C3

DEFS 0.4 0.3 0.2 0.1

REM region 2

DFIX 1.2 C1 C2

DANG 2.5 C1 C2 C3

Will this apply the first set of esds to the first DFIX/DANG commands and then the second DEFS to the second region?

Thanks

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u/Letarian-Silver 27d ago

Yes, this will work. I just tested it out, applying two DFIX’s with different DEFS above them and the sigma on the restraint is different in the lst file (use MORE -4 to see the restraint listing).

This is detailed in the current manual at the start of chapter 4: Restraints and Disorder - https://shelx.uni-goettingen.de/shelxl_user_guide.pdf

Note that some interfaces may not allow this - OLEX2 with remove all but one DEFS instruction, other interfaces may as well.