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Re: [ccp4bb] crystallisation and mosaicity |
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CCP4bb navigationCCP4bb <-- 2008 <-- June 2008 <-- 04 June 2008Subject: Re: crystallisation and mosaicity From: Charlie Bond Charles {- dot -} Bond {- at -} UWA {- dot -} EDU {- dot -} AU Date: 2008-06-04 dunking into liquid nitrogen is that a cushion of nitrogen gas persists around the crystal/loop so that 'freezing' is not so reproducible (hopefully an expert will elaborate on this). The same problem doesn't exist with liquid propane, but it has other issues... I generally default to using the cryostream unless I know by experiment that dunking works. Cheers, Charlie Ohren, Jeffrey wrote: > Could it be that evaporation on the way from the microscope to the cold > stream increases the effective cryo concentration as well as causing a > beneficial dehydration effect? > > There are quite a few publications that have carefully evaluated > optimizing cryo cooling. Check out Elspeth Garman's many excellent > papers on the subject as well as J. Appl. Cryst. (2006). 39, 244-251; > Methods 34 (2004) 415-423 and Acta Cryst. (2002). D58, 459-471, to name > a few. > > Jeff > > -----Original Message----- > From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of > Paul Paukstelis > Sent: Tuesday, June 03, 2008 11:59 PM > To: CCP4BB@JISCMAIL.AC.UK > Subject: Re: [ccp4bb] crystallisation and mosaicity > > I have also observed this. In my cases I have also been able to get away > > with using less cryoprotectant when freezing in the cryostream. > > --paul > > Daniel Pomeranz Krummel wrote: >> Dear Sajid, >> >> I have observed a consistent reduction in mosaicity (from approx. 0.95 > to >> 0.45) for one case by freezing the crystals in a cryostream (N2 > vapour) as >> opposed to submerging in liquid nitrogen. >> >> Have others observed this? >> >> Daniel >> >>> Dear All >>> >>> My protein size is ~30kD and crystallizes with >>> 19%Peg3350, 0.2M Nacl, and 0.1M Na Cacodylate buffer. >>> >>> Please refer the attached crystal image with this. The >>> crystal looks like good enough for home source. These >>> crystals appears in 4-5 days at room temp. >>> >>> Sometimes I'm getting crystals like this, but very few >>> in 24 well tray. Most of the time, I found the drop >>> contains needles. If I reduce the precipitant little >>> bit, I wont find any change in the drop even after >>> long time. Changing pH (or temp)of the buffer does not >>> help me any better. The crystal appears only around >>> 5.5pH. >>> >>> The problem is mosaicity. This crystal diffracted in >>> home source upto 3.2A and the mosaicity is 2.5degree. >>> Almost all the good crystal like this having same >>> mosaicity. >>> >>> Good cryo condition so far that I found was >>> 10%Glycerol with mother liquor. Other conditions >>> weekens the diffraction quality or increase mosaicity. >>> >>> In many crystal I could see some crack in the middle >>> of the crystal, it looks like twin crystal. Or the >>> crystal appears with some sattelite crystals. >>> >>> Can anyone suggest me some good way to overcome these >>> problems. >>> >>> Thankz >>> >>> Sajid >>> >>> >>> >>> From Chandigarh to Chennai - find friends all over India. Go to >>> http://in.promos.yahoo.com/groups/citygroups/ >>> >> > > > . > -- Charlie Bond Professorial Fellow University of Western Australia School of Biomedical, Biomolecular and Chemical Sciences M310 35 Stirling Highway Crawley WA 6009 Australia Charles.Bond@uwa.edu.au +61 8 6488 4406 CCP4bb navigationCCP4bb <-- 2008 <-- June 2008 <-- 04 June 2008 |
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