Re: [ccp4bb]: translational NCS

["M. Sundaramoorthy" <sundar@buerger.kumc.edu>]

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> but I managed to build the model manually, and have refined
> a couple of cycles so far. The 2fo-fc and fo-fc maps have  
> showed many new and nice features, which is encouraging, 
> but R/Rf is about 41/45.  
> 
	Do you use sigma cutoff in your refinement?. If the answer is yes,
	you might be throwing out more 2n+1 reflections than 2n
	reflections. That will introduce a serious systematic error. The
	best thing will be to use all the reflections including the ones
	with negative intensities. I haven't used REFMAC so far. So I am
	not sure if it can handle negative intensities. You may use
	SHELXL.

	As few others suggested, it may be a good idea to transform the
	lattice using some kind of soaking. We had a situation where heavy	
	atom soaking changed to smaller cell with no loss in the 
	diffraction quality and resoulion. 

	Similar was the experience with cocrystallizatin with heavy metal
	compounds in at least one case I read. In that case, there was
	even a great increase in the resolution ( Ref: Ronning et al.
	(2000) Nat. Struct. Biol. Vol. 7, 141-146.

	Another useful reference regarding pseudo-translation problem is
	Chook et al. (1998). Acta Cryst. D54, 822-827.

	Sundar