Well - it is pretty tricky to get reliable anomalous signal after
detwinning, but I guess you can try!
There are 2 ways I would test - one is detwin assigning I+ and I- - it
is meant to handle the anom pairs correctly.. You can input the twin
operator and the twin factor.
Then SFCHECK will also detwin data - but you will need to read the
manual to see if it will handle anomaous data properly..
Eleanor
Jordi Benach wrote:
Hi,
I just got a MAD dataset (~2.5A) of a crystal that so far seems to
belong to P31 or P32 space group and that also scales pretty well
in P3121 or P3221. According to the UCLA twinning server, the
P31/P32 crystal is merohedrally twinned with a twinning fraction of
0.33 and following a twinning operation h,-h-k,-l. CNS gives a
twinning fraction of 0.42.
Although we have solved twinned crystals in the lab with similar
twinning fractions/resolution in the past using SOLVE or BnP/SHELX,
only realizing that the crystal was twinned during refinement when
the R values wouldn't go down.
In this P31/P32 case, however, I can't solve the twinned data with
any program, or at least I can't get interpretable electron density
maps. Any ideas, clues? Is there a way to get a program that will
detwin raw intensity data (like *.sca files directly from
scalepack)?
Thanks,
Jordi
