Hi Flip, sfcheck will consider some twinning relationships not investigated by the servers
for sfcheck version 7: %sfcheck
outputdir/
FILE_F my.mtz OUT U TEST Y <blank line> This will generate a postscript report including a potential twin law, if found. As you've implied other factors can lead to an apparent relationship between reflections, including scaling in the wrong space group, and this possibility will have to be eliminated separately. Also examine your spot morphology - if some of the streaky spots look 'split', then you may have a case of non-merohedral twinning. A particularly frustrating protein I worked with, that I strongly suspect as being non-merohedrally twinned, would give a appreciably different apparent twin fraction when I tweaked parameters at the spot integration stage, consistently across several crystals. Good luck! James Dr. James Irving NH&MRC C.J. Martin Fellow Division of Structural Biology Wellcome Trust Centre for Human Genetics Oxford University Roosevelt Drive, Oxford OX3 7BN UK email: [EMAIL PROTECTED] phone: +44 1865 287 550
