Hi, Phaser is pretty robust now if you have 2-fold tNCS (indicated by having only one large non-origin peak in the native Patterson map), and recent versions are better at dealing with higher order tNCS (i.e. 3 or more copies related by multiples of a single translation vector). However, getting higher order tNCS to work properly can take a bit more thought and analysis outside the program, and if you're unlucky enough to have 2 or more different independent tNCS vectors it's not sophisticated enough to deal with that.
One common problem is that tNCS interferes with proper space group identification. For instance, it can be difficult to tell whether you have a crystallographic 2(1) screw axis with a parallel NCS 2-fold, or crystallographic 2-fold with parallel NCS screw axis. Both of these will lead to tNCS, but one will be much closer to reality. Also, tNCS can obscure the detection of twinning, and sometimes a crystal has both pseudo-symmetry with twinning as well as tNCS. If you want to send me a Phaser log file (off-list), I might be able to make some suggestions about what to consider. Best wishes, Randy Read > On 8 May 2018, at 16:02, 苏纪勇 <sujy...@nenu.edu.cn> wrote: > > Dear Herman, I tried phaser. It worked. But there are a lot of crashes in the > structure. Meanwhile, R factors could not be lowered. I tried to use P1 to > process the data, but I do not know how many monomers in the asymetric unit. > Bests, JiYG > On 05/08/2018 22:50, herman.schreu...@sanofi.com > <mailto:herman.schreu...@sanofi.com> wrote: > Dear JiYG, > > Unless the tNCS has caused processing problems, Phaser should automatically > deal with tNCS and I would recommend to just give it a try. If it fails, you > could try more sophisticated approaches. > > Best, > Herman > > Von: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] Im Auftrag von ??? > Gesendet: Dienstag, 8. Mai 2018 16:41 > An: CCP4BB@JISCMAIL.AC.UK > Betreff: [EXTERNAL] [ccp4bb] tNCS problem > > Dear all, Recently, I collected a data set of a crystal of a big protein, > which contains 1000 amino acids. I processed the data to P2. But the data set > has tNCS problem. I want to do molecular replacement. Is there anyone know > how to deal with this problem? Thanks, JiYG > > ------ Randy J. Read Department of Haematology, University of Cambridge Cambridge Institute for Medical Research Tel: + 44 1223 336500 Wellcome Trust/MRC Building Fax: + 44 1223 336827 Hills Road E-mail: rj...@cam.ac.uk Cambridge CB2 0XY, U.K. www-structmed.cimr.cam.ac.uk
