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CCP4bb navigationCCP4bb <-- 1999 <-- November 1999 <-- 30 November 1999Subject: Fwd: Spooky, moving crystals From: Richard Gillilan reg8 {- at -} CORNELL {- dot -} EDU Date: 2008-07-21 I recently had exactly this problem only I caught the crystal frozen in the act of being catapulted out of the loop. I was using a thicker- than usual oil for cryoprotectant and kept seeing empty loops with what looked like long clear hairs attached. Finally, one loop had a graceful arc of frozen oil and on the very tip was the crystal! I wish I have taken a picture of it. There is an optimum magnet strength. To strong and you have problems like this, too weak and you find that users are knocking their base off the mount when they disengage the cryotongs. Especially in confined spaces, weak magnets are a problem. Richard Gillilan MacCHESS > > > On Jul 21, 2008, at 2:39 PM, Edward Snell wrote: > >> This reminded me of a haunted beamline that removed crystals from >> the loop. >> >> You'd loop the crystals up nicely, block the stream, transfer the >> crystal fast to the goniometer head, unblock the stream then look >> in the microscope - no crystal! After a few tries (and head >> scratching) the culprit was discovered to be a Hampton strong >> Magnetic Base that flipped the crystals out of the loops when you >> were mounting the pin. It was so strong that the pin 'clicked' >> onto the magnet. Interestingly, looking below the goniometer head, >> there was a whole graveyard of dead crystals lying there - many >> other users had the same problem. The magnet was replaced with a >> Hampton light magnetic base and the problem went away completely. >> With the concurrence of the beamline scientist the light base >> remained with the beamline for many years until a recent upgrade >> when they replaced the user with a guy called Sam. >> >> Of course, no names and no synchrotrons will be revealed ;) >> >> Seriously though, 10 to 20 minutes until the sample stops moving >> sounds very ominous. I may have misunderstood, but it sounds like >> you are warming the crystals for data collection after >> cryomounting them? Once cooled they should remain that way. >> >> Cheers, >> >> Eddie >> >> Edward Snell Ph.D. >> Assistant Prof. Department of Structural Biology, SUNY Buffalo, >> Hauptman-Woodward Medical Research Institute >> 700 Ellicott Street, Buffalo, NY 14203-1102 >> Phone: (716) 898 8631 Fax: (716) 898 8660 >> Email: esnell@hwi.buffalo.edu Telepathy: 42.2 GHz >> >> Heisenberg was probably here! >> >> >> -----Original Message----- >> From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf >> Of Kevin Jude >> Sent: Monday, July 21, 2008 2:20 PM >> To: CCP4BB@JISCMAIL.AC.UK >> Subject: Re: [ccp4bb] Spooky, moving crystals >> >> I've seen haunted crystals before - the culprit was indeed with the >> mounting of the pins in their bases (I was re-using some pins and >> apparently the adhesive had cracked or otherwise failed). >> Fortunately I >> never leave home without a tube of Duco cement and was able to >> correct >> the problem in situ. >> >> kmj >> >> Mark J. van Raaij wrote: >>> Dear all, >>> >>> in a recent synchrotron trip we had a problem with our crystals >>> moving >>> after mounting them onto the goniometer, in some cases they moved >>> out of >>> the beam and even out of the zoomed camera picture - it seemed >>> the pins, >>> upon equilibrating to room temperature, extended. It happened with >>> pre-mounted litho-loops only, not with pre-mounted mitegen loops >>> on the >>> same trip, so one possible cause is different metal allows used >>> in the >>> pins, somehow the mitegen ones being more suitable. >>> >>> We used two-component glue to stick the pins into the metal bases >>> (Spine), so that might be another possible culprit. Perhaps we >>> did not >>> allow sufficient time for the glue to react before freezing into >>> liquid >>> N2 and it continued its reaction upon thawing, somehow pushing >>> the pin a >>> bit out of the base. In this case the difference between >>> litholoops and >>> mitegen loops may have been the thickness of the pins, the latter >>> somehow allowing expansion of the glue along the sides, the >>> former not. >>> >>> In any case, I am wondering if any of you has seen this before, >>> so we >>> know how to avoid it in the future. >>> In some cases, it took 10-20 min. for the crystal to stop moving, >>> which, >>> with the current data collection speed and robotic mounting, is >>> significant. Fortunately, it did not affect our trip too much, as >>> we has >>> sufficient time in the end. >>> >>> Greetings, >>> >>> Mark >>> >>> Mark J. van Raaij >>> Dpto de Bioquímica, Facultad de Farmacia >>> Universidad de Santiago >>> 15782 Santiago de Compostela >>> Spain >>> http://web.usc.es/~vanraaij/ > CCP4bb navigationCCP4bb <-- 1999 <-- November 1999 <-- 30 November 1999 |
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