As Randy pointed out, you should check Patterson map for off-origin peaks. There is also a small chance that you actually have P2 - systematic absences may result from tNCS nearly colinear with crystallographic axis.
On Thu, 2012-04-19 at 14:20 +0800, LISA wrote: > Hi all, > > I am trying to solve one structure by molecular replacement with > phaser in CCP4. This a complex of a multi-domain domains with small > ligand. I have structues of this protein in apo state and with other > similar ligand. The space group of this crystal is P21. This crystal > should have 4 molecules in ASU. I used the full protein as model but > did get any sol and LLG is below zero. Then each domain were used as > the search models in phaser with rotation and tranlsation. I can the > get high z score (>20), and LLG is raising. It looks like I get the > right sol, but it have more 50 clashes. Why phaser give wrong sol > with so high z socre? Can anyone give me some suggestion to solve my > strucutes? Thank you. > Best > > Lisa -- "I'd jump in myself, if I weren't so good at whistling." Julian, King of Lemurs