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 <jubo...@jhsph.edu> 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/Proteincrystalscanbeincommensurate > lymodulated.pdf > > Petr > > > > On 10/29/10 6:08 PM, "David Goldstone" <david.goldst...@nimr.mrc.ac.uk> > wrote: > > Dear All, > > Does anyone have any insight into what the circles around the spots > > might be? > > cheers > > Dave > > > -- Professor John R Helliwell DSc
