Unfortunately, some crystals don't diffract at all. You may want to try to 100% verify that it's protein either by SDS-PAGE or mass-spec (100x100x100 micron crystal could contain ~0.5mcg of protein, so you my need to use silver staining). If it is, I'd consider trying to get diffracting crystals by
a) dehydration (chances are slim since you have no diffraction at all) b) microseeding c) additive screen (SilverBullets?) d) screening a lot of crystals (how small are the small ones? They may be good enough for microfocus beamlines and yes, smaller crystals generally tend to produce better diffraction quality) e) this one sounds silly, but make sure you are hitting the crystal with the beam (just shift it up and down a notch and take single shot - I've seen this "trick" actually working several times) The list is not comprehensive. But frankly, having non-diffracting crystals is a poor place to start, these guys waste a lot of time and often still don't diffract no matter what you try. Good luck, Ed. On Mon, 2010-08-30 at 21:24 -0400, qiangm zhang wrote: > Hi all, > > I got a crystal of one membrane protein (~60kD) from Na/K > phosphate condition (see getit_4), then I got the improved crystal > like getit_5 after trying seeding, different detergents, lipids and > additives. But this crystal does not diffract at all, I already tried > Izit staining which shows it is protein crystal (detergent crystal?). > Does anyone have any good suggestions for the optimization of this > membrane protein crystallization? Thank you in advance. > > > Best regards > > Qiangmin Zhang > > Biomedical Science Tower 3 > Room1034 > 3501 Fifth Avenue > Pittsburgh, PA 15260 > > > > > > > -- > 张强敏 -- Edwin Pozharski, PhD, Assistant Professor University of Maryland, Baltimore ---------------------------------------------- When the Way is forgotten duty and justice appear; Then knowledge and wisdom are born along with hypocrisy. When harmonious relationships dissolve then respect and devotion arise; When a nation falls to chaos then loyalty and patriotism are born. ------------------------------ / Lao Tse /
