hi Ngo, Reduce such showering by increasing the reservoir volume, or by increasing the protein concentration.
On Wed, Apr 16, 2008 at 4:08 PM, Van Den Berg, Bert < [EMAIL PROTECTED]> wrote: > Hi Ngo, > > your needles actually look like very thin plates. They seem promising to > me. From appearance its impossible to tell whether the crystals are > detergent or not. DDM is apparently known to form crystals, but I've never > really gotten any (DDM is very soluble). What temperature have you used? 4C > would favor forming DDM crystals. The round crystals are often seen in > membrane protein crystallization. They generally don't diffract, contain a > lot of detergent (maybe all detergent) and are very hard to get better (ie > get sharp edges and/or diffraction). > What I would do at this point is trying to get the needle/plate crystals > better (by using 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). For now I would go with the assumption that the crystals are protein. > > Good luck! > > > 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]://www.umassmed.edu/pmm/faculty/vandenberg.cfm > > > ------------------------------ > *From:* CCP4 bulletin board on behalf of Ngo Duc Tri > *Sent:* Wed 4/16/2008 9:48 AM > *To:* [email protected] > *Subject:* Re: [ccp4bb] Optimization of needle crystals? > > Dear experts, > > > You didn't mention which detergent in the conditions. From the picture it > > looks > > like crystals of detergent. > > > > > The initial buffer contains 50mM Tris 7.7, 100mM NaCl and 0.015% DDM. > > I got two forms of crystal: needle and round shape. > The needle crystals grow from conditions containing Mg2+ salt and high pH. > The round crystal grow from conditions containing Mg2+, high pH and small > PEG. > > I already fail to optimize the round shape (by changing the PEG > concentration as well as pH or protein concentration). So that's the reason > why I think about optimization of the needle form. > > Here I attach more pictures to show you the needle and the round crystal. > I never applied powder diffraction before so maybe it's hard for me to > confirm it's the crystal of detergent or not. > > Thank you very much for all of your helpful suggestion! > > My best regards, > TriNgo > PhD Student- Sungkyunkwan University, Korea > -- S.Jayashankar Research Student Institute for Biophysical Chemistry Hannover Medical School Germany
