Heng-- Two things you might want to try:
1. Drop ratios with your current conditions and DMSO additive. Use different concentrations of DMSO too. 2. Try using Hampton Crystal Screen and Crystal Screen 2 as additives. I generally do this by adding 5% of XS 1 & 2 to the wells. Once I find one of these reagents that improves crystal quality/diffraction, I optimize the concentration for that. You can do this with the Mosquito robot for 96 well format....or in the 24 well VDX trays. Hope this helps! annie Annie Hassell Glaxo Smithkline 5 Moore Drive RTP, NC 27709 919/483-3228 919/483-0368 (FAX) annie.m.hass...@gsk.com "HanJie_HCT Tai" <chemtai2...@hotmail.com> Sent by: "CCP4 bulletin board" <CCP4BB@JISCMAIL.AC.UK> 17-May-2009 08:27 Please respond to "HanJie_HCT Tai" <chemtai2...@hotmail.com> To CCP4BB@JISCMAIL.AC.UK cc 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 Live?: Keep your life in sync. Check it out.
