Something to add into this discussion is also go fro the tiny crystals versus the big ones. BIGGER is not always BETTER - in particular if you try to freeze directly out of your conditions without an additional cryo-protectant. And with small or tiny I mean 10 micron, whatever you are capable of mounting. It is also important to keep the amount of liquid volume around the crystal low, so rather use a loop in which you scoop the crystal up instead of having a large loop with lots of liquid.
Then one last remark, LN2 versus cryo-stream freeze. Dipping in LN2 leads to a quicker freeze of your material. If you have the option to anneal your crystal after testing it in the beam try it out and assess the success or damage, this will be very different depending on what cryo-additives you have around. Good luck, Jürgen On Feb 7, 2012, at 9:28 AM, Jacob Keller wrote: One last thing--sometimes crystals can be frozen as is, particularly if you use mitegen mounts and get nearly all of the mother liquor off the crystals by dabbing the loop on the dry surface next to the drop several times. So simple it is always worth a try.... JPK On Tue, Feb 7, 2012 at 2:37 AM, Mark J van Raaij <[email protected]<mailto:[email protected]>> wrote: Rationalising it completely may only be possible once you know the nature of the crystal contacts, i.e. when you have solved the structure. Until then it is mainly a matter of experimenting. -----Original Message----- From: CCP4 bulletin board [mailto:[email protected]] On Behalf Of Theresa H. Hsu Sent: Monday, February 06, 2012 11:00 PM To: [email protected]<mailto:[email protected]> Subject: Re: [ccp4bb] Freezing crystal Hi all Thanks for all the suggestions which I will try soon. How do the crystallization condition (PEG vs. salts like ammonium sulfate) affect the croyprotectant condition? Do factors like presence of low concentration of high molecular weight PEG (> 2000) mean PEG is better? Do buffers and salts in protein also important? Trying to rationalize it :) Theresa -- ******************************************* Jacob Pearson Keller Northwestern University Medical Scientist Training Program email: [email protected]<mailto:[email protected]> ******************************************* ...................... Jürgen Bosch Johns Hopkins University Bloomberg School of Public Health Department of Biochemistry & Molecular Biology Johns Hopkins Malaria Research Institute 615 North Wolfe Street, W8708 Baltimore, MD 21205 Office: +1-410-614-4742 Lab: +1-410-614-4894 Fax: +1-410-955-2926 http://web.mac.com/bosch_lab/
