I wonder whether flash-cooling from -10 degC would preserve those low mosaicity values?
JPK From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of mesters Sent: Thursday, February 06, 2014 8:40 AM To: CCP4BB@JISCMAIL.AC.UK Subject: Re: [ccp4bb] Room temperature data collection Hello Theresa, long time ago, we were having severe problems freezing crystals of a human carboxypeptidase (GCPII). At room temperature and at 4 degrees celcius (capillary mounted), we could only collect 2 to 3 images at X13 in Hamburg and that was it (we had no useful vitrification conditions, freezing killed the diffraction). I cannot recollect why but on one of the synchrotron trips we started to ramp the cryo-system to zero, -5, -10, and -15 degrees celcius (capillary mounted crystals from droplets with 200 NaCl, 5% (w/v) PEG 400, and 15% (w/v) PEG 1500). The capillaries were kept very short to circumvent condensation problems. At zero degrees, the crytsals lasted slightly longer. At -5 degrees Celcius we obtained about 40 images before the crystal was dead. At -10 degrees celsius, we finally managed to get useful datasets. At -15 no diffraction at all but the crystal did not appear frozen. We can guess what exactly happened but I like to think the solution got really viscous at -10 degrees celcius which in turn kept the radicals from moving around and destroying the crystal lattice (sort of like freezing)... Later, Alex McPherson told me that datasets of crystals of viruses were (and still are?) commonly collected at slightly sub-zero temperatures. I was unaware fo this method and "rediscovered" it by endless trail and error. The most notable thing about lowering the temperature from zero/-5 to finally -10 was the mosaicity, I have never seen values that low (0.06) in any of my structures before and thereafter (solvent content of crystals was 63,8% and packing interactions in one direction were limited). - J. - Am 06.02.14 10:51, schrieb Theresa Hsu: Dear crystallographers Just out of curiosity, is it possible to collect datasets from crystals at room temperature at synchrotron? Are fast detectors like Pilatus useful for this? Thank you. Theresa -- Dr. Jeroen R. Mesters Deputy and Group Leader Institute of Biochemistry, University of Lübeck Ratzeburger Allee 160, 23538 Lübeck, Germany phone: +49-451-5004065 (secretariate 5004061) fax: +49-451-5004068 http://www.biochem.uni-luebeck.de<Http://www.biochem.uni-luebeck.de> http://www.iobcr.org<Http://www.iobcr.org> [cid:image001.png@01CF2318.F15F36D0]
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