Another possible, and easy, way to optimize initial hits is to take your hit condition in the reservoir and add small volumes (say 10% or so) of other screen solutions. In this way you get small deviations from the initial hit condition that may lead to better crystals or at least gives you hints as what to try next. The only thing to watch out for is incompatibilities that could lead to salt crystals.
Bert van den Berg University of Massachusetts Medical School Program in Molecular Medicine Biotech II, 373 Plantation Street, Suite 115 Worcester MA 01605 Phone: 508 856 1201 (office); 508 856 1211 (lab) e-mail: [EMAIL PROTECTED] http://www.umassmed.edu/pmm/faculty/vandenberg.cfm -----Original Message----- From: CCP4 bulletin board on behalf of Ngo Duc Tri Sent: Thu 4/17/2008 4:09 AM To: CCP4BB@JISCMAIL.AC.UK Subject: [ccp4bb] SUMARY: Optimization of needle crystals Dear ccp4 Users, I would like to say thank you to all of your valuable advices to optimize the needle crystal and related problems when dealing with membrane protein. Here I report the summary of your advices to help other students who got the same problem: 1. Additive screening from Hampton Research maybe useful in some cases. 2. Can apply techniques/tricks that are used for soluble proteins, such as vary Mg2+ salt conc and identity, temperature, volume/reservoir ratio, protein conc. and even trying different detergents and/or mixtures including DDM 3. Round shape crystal is maybe detergent crystal, but other opinion shows that DDM cannot create crystal in aqueous solution. I am still confused about this problem but it's hard to optimize these kind of crystal. 4. Try to collect data on the micro-diffraction beamline (but the facilities is only available in US and Europe). 5. Powder diffraction also can be used to check the protein crystal or detergent crystal and even solve the structure. Thank you very much for your advices and suggestion! My best regards, TriNgo PhD Student- Sungkyunkwan University, Korea