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:[EMAIL PROTECTED] 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/ >> > >
