OK! John prompted me to look more carefully at the images and they don't seem to be consistent with any optics or detector effect.
Attached a Blowup (almost as strange as Antonioni's 1966 film with this name) of one of the areas. As others have pointed out already, the features are not round halos surrounding the spots though they look like this at first glance. They seem to consist of fuzzier subsidiary spots. If these spots were oriented in a 6 fold manner, this would, I think be consistent with a commensurate modulation with q=0.5a* (assuming the subsidiary spots are half way between the main spots). However, there seems to be some evidence that the subsidiary spots around each main spot are 30 degrees apart not 60 degrees. A bit difficult to see though. Looking at the movie, I think they are most visible for zones with constant l (h and k varying) though they presumably occur elsewhere. I presume the indexing would reveal this. It might be worth trying to index on a supercell with a=146A and see if there is anything left. Regards Colin > -----Original Message----- > From: CCP4 bulletin board [mailto:ccp...@jiscmail.ac.uk] On > Behalf Of John R Helliwell > Sent: 03 November 2010 17:00 > To: CCP4BB@JISCMAIL.AC.UK > Subject: Re: [ccp4bb] Strange spots > > Dear David, > Many thanks indeed for this movie and the extra info. > It is quite captivating! > > The 'strange spot' features do seem progress to other regions > of reciprocal space at approximately constant diffraction > resolution in an anti-clockwise manner.....but I am still > digesting your movie.... > > Behind the scenes discussion, between Colin Nave, James > Holton and myself, has been going on. Since Colin has been > the main leader in these I leave it to Colin to take it up > from here and I can chip in if I can add anything. > > Greetings, > John > > On Wed, Nov 3, 2010 at 3:53 PM, David Goldstone > <david.goldst...@nimr.mrc.ac.uk> wrote: > > Dear All, > > > > Thank you for the replies sorry about the delay in my > reply. Here is > > some more information, for those of you that are interested, to try > > fill in some gaps. > > > > The data was collected on our home source with osmic > vairmax-HF optics > > and an RAXISIV++ detector. We are investigating whether it is an > > optics issue but this is unlikely as other crystals in the > screening > > run didn't display this phenomenon. > > > > The crystal was grown in the presence of 12% glycerol and > transfered > > to 20% glycerol as a cryo. I haven't tried other cryos as crystals > > also grow in 20% glycerol and do not require further cryoprotectant. > > > > I have uploaded a movie showing a wedge of data showing how the > > circles around the spots progress. > > http://www.4shared.com/video/o8_YmInD/Spot_defect.html (~12mb > > download) > > > > The crystals index and scale in p6122 (a=b=73, c=110) with a single > > monomer in the ASU (by matthews, 45% solvent). We do however see a > > peak in the native patterson at (0,0,0.2 ~50% origin height). > > > > Cheers > > > > Dave > > > > > > On 29/10/2010 17:08, David Goldstone wrote: > >> > >> Dear All, > >> > >> Does anyone have any insight into what the circles around > the spots > >> might be? > >> > >> cheers > >> > >> Dave > > > > -- > > David Goldstone, PhD > > National Institute for Medical Research Molecular Structure The > > Ridgeway Mill Hill London NW7 1AA > > > > > > -- > Professor John R Helliwell DSc >
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