Michael, yes sorry I had (temporarily) forgotten about LABELIT. In the pseudo-precession image in the article (Fig. 3a) one can clearly see the TDS streaks along the axes which could easily fool you into misassigning the space group if all you have are the integrated intensities. Very nice!
Cheers -- Ian On 15 March 2013 17:10, Michael Thompson <[email protected]> wrote: > As a follow up to Ian's suggestion, the LABELIT software (sorry for a > non-CCP4 suggestion) will create artificial precession images from your raw > oscillation images. > > Documentation can be found here: > > http://adder.lbl.gov/labelit/ > > And an article describing the functionality can be found here: > > http://cci.lbl.gov/publications/download/CCN_2011_p15.pdf > > Hope it helps, > > Mike > > > > > > > > ----- Original Message ----- > From: "Ian Tickle" <[email protected]> > To: [email protected] > Sent: Friday, March 15, 2013 8:51:47 AM GMT -08:00 US/Canada Pacific > Subject: Re: [ccp4bb] space group determination problem > > > > > > > Hi Gengxiang, > > Personally I find it impossible to reliably assign a space group from > integrated reflections because you just don't know if the apparent > systematic absence violations are due to a TDS streak or overlapping > neighbouring strong spots. "In the old days" (i.e. when we had precession > cameras) we would never do this: we would look at the images and see if > there was actually a spot at the Bragg position. Now technology has > "advanced" and with rotation images it's much harder to do this. Maybe it's > possible to make pseudo-precession images? > > What I would do is assume the worst and assign it temporarily as P422; > then let the HA or MR program sort out the space group by trying all the > possibilities; it's only CPU time after all! > > > My 2p's worth. > > -- Ian > > > > > On 15 March 2013 15:09, gengxiang zhao < [email protected] > wrote: > > > Dear CCP4s, > > I am looking for more experienced concerns to determine which space group > my crystal is. At present, we take it as P42212 (#94). > > HKL is below: > > Intensities of systematic absences > h k l Intensity Sigma I/Sigma > > 0 0 9 -58.6 40.8 -1.4 > 0 0 11 -204.4 53.9 -3.8 > 0 0 13 -57.1 62.8 -0.9 > 0 0 15 -470.6 92.7 -5.1 > 0 0 17 -626.1 105.1 -6.0 > 0 0 19 -64.7 62.4 -1.0 > 0 0 21 266.6 75.9 3.5 > 0 0 23 1372.4 116.4 11.8 > 0 0 25 -543.9 84.8 -6.4 > 0 0 27 -396.8 93.1 -4.3 > 0 0 29 -598.8 102.1 -5.9 > 0 0 31 617.4 116.2 5.3 > 0 0 33 445.4 93.8 4.7 > 0 0 35 -64.5 89.5 -0.7 > 7 0 0 -241.4 134.7 -1.8 > 9 0 0 -375.8 55.5 -6.8 > 11 0 0 -39.1 61.8 -0.6 > 13 0 0 -356.1 78.1 -4.6 > 15 0 0 -262.6 65.6 -4.0 > 17 0 0 -324.7 89.3 -3.6 > 19 0 0 -178.7 88.5 -2.0 > 21 0 0 -726.3 115.3 -6.3 > 23 0 0 -189.4 131.0 -1.4 > 25 0 0 157.7 157.5 1.0 > 27 0 0 -591.5 213.4 -2.8 > 29 0 0 -111.7 198.4 -0.6 > 31 0 0 -94.2 247.0 -0.4 > 33 0 0 -169.8 306.5 -0.6 > 35 0 0 -71.2 347.8 -0.2 > 39 0 0 -82.8 417.9 -0.2 > > > Thanks a lot. > Best Wishes, > Gengxiang > > -- > Michael C. Thompson > > Graduate Student > > Biochemistry & Molecular Biology Division > > Department of Chemistry & Biochemistry > > University of California, Los Angeles > > [email protected] >
