Have you tried different cryoprotectants? Can make a huge difference. Also, have you shot an xtal at room temp - to see what the intrinsic diffraction limit is? Additive screens? If all else fails you may well need to explore a different expression construct.
Tony. Sent from my iPhone On 1 Aug 2012, at 19:52, "Yi-Liang Liu" <yiliang...@gmail.com> wrote: > Hi CCP4BBers, > > I have a protein crystallized with 0.2mM Mg acetate and PEG 8000 or 0.1mM > cacodylate, pH 6.5, 0.2 Mg acetate, PEG 3350. Both of the conditions gave > triangle pyramid like crystals. I brought the crystals to synchrotron using > 30% PEG 400 as cryoprotactant, the resolution was only be able to reach 4A or > worse. I have tried changing pH and concentrations of PEG, PEG types. I found > out this crystal only grew between pH 6.5~7.5 and PEG types did not change > the result of diffraction dramatically. I have also tried the seeding (break > it down and reseed in the same condition. Maybe I did it wrong?). It gave me > the similar results, not improving. Is there any simple way of improving it > before jumping into reengineering the protein. > > Thanks, > > Lucas
