The detector issue could be resolved by moving it to a different distance and recording the pattern again.
In the absence of further info, my vote goes for James Holton's explanation - the effect could be due to optocal misaligenment
Colin
> -----Original Message-----
> From: CCP4 bulletin board [mailto:[log in to unmask]] On
> Behalf Of John R Helliwell
> Sent: 31 October 2010 12:47
> To: [log in to unmask]
> Subject: Re: [ccp4bb] Strange spots
>
> Dear Jurgen and Petr,
> I looked at the Princeton incommensurate link kindly provided by Petr.
> I see your point ie examples of a grouping of subsidiary
> spots around a central spot. But not continuous circles.
>
> I have now checked the Atlas of Optical Transforms (my office
> copy en route to Manchester United versus Tottenham Hotspur
> yesterday evening). Little help there.
>
> I also looked at Richard Welberry's Diffuse Scattering book
> (OUP/IUCr Monograph). This has a variety of
> circular-continuous halo effects from inorganic, and one
> organic, crystals and explanations of the crystal disorders
> they arise from; these halo effects seem identical to David
> Goldstone's.The main difference of the Welberry examples
> versus the David Goldstone example is the latter is
> restricted to one part of reciprocal space, at least from the
> one pattern shown.
> Basically we need more info from David Goldstone re the
> fidelity of his detector, pointed out in the earlier
> discussions as well, and/or more diffraction patterns,
> ideally as a movie clip of patterns as his crystal is rotated.
>
> Greetings,
> John
>
>
> On Sat, Oct 30, 2010 at 5:06 PM, Jürgen Bosch
> <[log in to unmask]> wrote:
> > I second Petr's opinion. These halos are different compared
> to John's book.
> > Strong reflections look perfect as can be seen in the red
> zoomed area.
> > weaker spots show the halos because the crystal lattice was
> disordered
> > (or because the crystals grew in a disordered or incommensurate
> > fashion). If you increase the contrast of the image you can
> see more
> > of those halos which have a sharp straight edge pointing at
> ~six corners around the spots.
> > The usual questions:
> > 1. how does the diffraction look like at room temperature
> in capillaries ?
> > 2. have you played with more than three different cryo's ? And what
> > was the result of it ?
> > 3. Is my assumption right, that you tried to freeze a large
> crystal ?
> > Try freezing a smaller one e.g. 50 µm and see how your high
> > resolutions spots behave. The rings we see are the typical
> remains of
> > weak ice rings ? Then you really should improve your cryo.
> > Jürgen
> >
> >
> >
> > -
> > Jürgen Bosch
> > Johns Hopkins Bloomberg School of Public Health Department of
> > Biochemistry & Molecular Biology Johns Hopkins Malaria Research
> > Institute
> > 615 North Wolfe Street, W8708
> > Baltimore, MD 21205
> > Phone: +1-410-614-4742
> > Lab: +1-410-614-4894
> > Fax: +1-410-955-3655
> > http://web.mac.com/bosch_lab/
> > On Oct 29, 2010, at 4:14 PM, Leiman Petr wrote:
> >
> > I think this is a poly-crystalline incommensurately
> modulated crystal, i.e.
> > incommensurately modulated crystal, which fractured upon freezing,
> > resulting in averaging of satellite spots.
> >
> > Fig. 3b from here:
> >
> http://www.princeton.edu/~actin/documents/Proteincrystalscanbeincommen
> > surate
> > lymodulated.pdf
> >
> > Petr
> >
> >
> >
> > On 10/29/10 6:08 PM, "David Goldstone"
> > <[log in to unmask]>
> > wrote:
> >
> > Dear All,
> >
> > Does anyone have any insight into what the circles around the spots
> >
> > might be?
> >
> > cheers
> >
> > Dave
> >
> >
> >
>
>
>
> --
> Professor John R Helliwell DSc
>
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