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: [EMAIL PROTECTED] Telepathy: 42.2 GHz Heisenberg was probably here! -----Original Message----- From: CCP4 bulletin board [mailto:[EMAIL PROTECTED] 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/
