Hmmm..I just fail to see 'lines' in that diffraction map. I see spots along something that could be segments of diffraction rings, i.e. a number of these crystals in some clustered random orientations, similar to ice as you mention. I also wonder how there could be true diffraction 'lines': If it is a small molecule or salt, then the diffraction spots are pretty far apart in reciprocal space, and the chance of seeing diffraction lines of closely spaced adjacent RL points like we see in the lunes of a (single X) macromolecular rotation image is quite remote. If for example that spot cluster down left would be a 'line', then the lattice spacing would have to be quite large. Why some of the low resolution rings are not exactly rings either can have various reasons we can discuss off board.
Otherwise no dissent. Best, BR From: Matthew Franklin [mailto:mfrank...@nysbc.org] Sent: Tuesday, July 24, 2012 7:08 AM To: b...@hofkristallamt.org Cc: Bernhard Rupp (Hofkristallrat a.D.); CCP4BB@JISCMAIL.AC.UK Subject: Re: [ccp4bb] Question about weird diffraction map Hi Bernhard - Having the spots in regular lines indicates that this is a single crystal diffraction pattern (to a first approximation). I have seen ice rings which contain a few strong spots, probably from microcrystals of ice, but I haven't yet seen ice diffraction that shows a lattice of spots. So, the presence of the spot lattice, plus the spots below 3.9 A, allow one to say that this image isn't ice diffraction on top of weak/absent protein diffraction. Ergo, this crystal is not a macromolecule. Plus, I was trying to show Zhao that the spots aren't just scattered at random. - Matt On 7/23/12 5:25 PM, Bernhard Rupp (Hofkristallrat a.D.) wrote: > you'll see that some of them are arranged in regular lines. I am not sure I understand what the line argument implies? >indicates a very small unit cell, with dimensions probably < 10 A Very indicative also the few strong and isolated high resolution reflections Cheers, BR -- Matthew Franklin, Ph. D. Senior Scientist New York Structural Biology Center 89 Convent Avenue, New York, NY 10027 (212) 939-0660 ext. 9374
