Dear Heng,
I assume you are growing your crystals using vapor diffusion. If your optimization efforts using various additives fail to give you suitable crystals you might consider trying to grow your crystals using a different technique. I would suggest a liquid diffusion based technique such as 1) the Granada box from Triana <http://www.trianatech.com/Eng/Home.htm> http://www.trianatech.com/Eng/Home.htm or 2) the Crystal Former from Microlytic <http://www.microlytic.com> www.microlytic.com. Several of our (Microlytic's) customers have been able to convert poor crystallization hits from vapor diffusion to well diffracting crystals using the Crystal Former. The liquid diffusion mixing kinetics allow a unique sampling of protein phase space compared to vapor diffusion techniques, and can consequently be considered an orthogonal crystallization tool. This may be what you need to grow well ordered crystals of your protein. - Morten From: CCP4 bulletin board [mailto:ccp...@jiscmail.ac.uk] On Behalf Of HanJie_HCT Tai Sent: Sunday, May 17, 2009 8:27 AM To: CCP4BB@JISCMAIL.AC.UK Subject: [ccp4bb] How to improve crystal which is twinning? Hi, I have a 22kDa protein that the floopy N & C terminus have been deleted. It was crystallized in 35%MPD/0.1m Tris (pH 8.5)/0.2M/(NH4)2SO4 in 2 - 3 days. Previously, a few small twining crystals were grown in this condition. I tried Hampton Research 96-additive screen . Additives such as glycerol, dioxane, etc didn't work well to improve/reduce twining issue. The 0.3% DMSO is the best additive I found that can grow a single crystal in the 1(pro)+0.8(buff)+0.2(add) drop. However, If looking careful under microscope it may be some other crystals growing inside that single crystal(hardly see under the microscope, but I can see it in other drops). I conducted the x-ray diffraction experiment for this 0.1x 0.1 mm crystal for which no cryoprotectant is required. The highest resolution is 2A but there are a lot of smear on the diffraction pattern. Thus, the index procedures failed due to the crystal quality. Do you have any brilliant ideas to improve the crystal growing condition in my case in order to get a truly single crystal? regards, Heng _____ Windows LiveT: Keep your life in sync. Check it out. <http://windowslive.com/explore?ocid=TXT_TAGLM_BR_life_in_synch_052009>
