Hi all, I am working a extremely difficult crystal whose resolution is low (3.5-4 A for native ) and could not be solved by MR. I am looking for some advice on data collection strategies, bellow are the details:
Say that I have a rod shaped xtal which is 50 um * 150 um * 20 uM, and if i use a 15um * 15 um beam size to shoot it, hopefully we can have 8 different site along the length to collect data. say that it take 60 frames (1 degree each ) before xtal decays significantly, if I collect 0-15 and 180-195 on the first site, and 15-30 (195-210) successively …., it is true that for each site, the Friedel paris are collected in a identical or close conditions, however how about the diffrences between each site? For my xtal, the unit cell and diffraction intensities could vary much from one end of the rod to the other end. Actually in my last attempt to collect on 3 different site of a single crystal, the scale factor and B-scale changes dramatically between the three site, as a consequence, high error model were used in scaling (0.1), and I assume that such a high error model is also detrimental for the small difference between Friedel pairs as when scaling the data from different site together, the signals get averaged out, am I right? Could anyone give me some advice on data collection strategy to maximize the possibility to get a useful peak dataset? I am also wondering if a high error model is also detrimental if I went for isomorphous phasing instead of anomalous phasing? Thank you for everyone’s wonderful advises in advance! Bei Dr. Bei Yang Postdoctoral Scholar UC Berkeley, QB3 360 Stanley Hall Berkeley, CA 94720
