[ccp4bb]: Waters at atomic resolution

["S. Parthasarathy" <spartha@sanketh.mbu.iisc.ernet.in>]

***  For details on how to be removed from this list visit the  ***
***    CCP4 home page http://www.dl.ac.uk/CCP/CCP4/main.html    ***



	Dear all,

	I am in the process of refining a TIM-ligand complex at
	1.1 ang. resolution. R-factor is around 17.0 and anisotropic
	refinement is yet to be done.

	I have few questions before I treat my atoms anisotropic.

	Data was collected at 100K.  There are quite a few waters
	which have B-values greater than 40 or so.  For some these
	waters electron density is not spherical suggesting that they
	may be moving around.  
	
	The question is do people apply any B-value cut-off to accept the
	waters ? if so what should be  the meaningful value for a data
	collected at 100K ?

	(OR)  If one want to treat these waters to have half occupacies
	what is the generally recommended B-values or u*u value ?
	and at what stage one should assign half occupancies, before
	or after anisotropic refinement ?

	looking forward to your replies,

	S.Parthasarathy
	Molecular Biophysics Unit
	Indian Institute of Science
	Bangalore 560 012 India.