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 <[log in to unmask]> 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" <[log in to unmask]>
To: [log in to unmask]
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 < [log in to unmask] > 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

[log in to unmask]