Hi Rui, Several things you can do:
1 - use a beam line with extremely high flux (here at ESRF it would be ID23-1 and ID-29) so that the crystal(s) give their uttermost diffraction before they notice that they are being hit by something "nasty" --- you usually get only very few high resolution diffraction frames doing that; 2 - use the additive screens that are available from several vendors. Blind screen, and you only select thos conditions that do not have the protein precipitate but give you crystals (few of them per crystallisation droplet), and test them for diffraction quality (we've had lots of success with this approach at IBS/LBM); 3 - more extensive screening of initial conditions to discover new hits. Fred. > Message du 05/02/10 05:39 > De : "rui" > A : CCP4BB@JISCMAIL.AC.UK > Copie à : > Objet : [ccp4bb] how to improve resolution > > Hi, All, > > We are trying to crystallize a protein and found some initial hit in the > following conditions, > > pH 4.8, 0.2 M AS or some other salts ( NaCl,LiCl, MgCl2 ), 32% PEG4000 or > PEG3350 ). However the quality of the crystal is not so great,some of them > look like needle cluster(very long in length), some of them look like > multi-crystals or hollow inside. We tried to optimize the pH and PEG and > tested one that diffracts at 2.9A. For the next, how to improve > resolution?Any suggestions? Even mutate the protein to get a high resolution > is ok, generally what kind of mutation would make proteins crystallize > better? Thanks. >
