[ccp4bb] difference density ripples around Hg atoms

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CCP4bb <-- 2007 <-- August 2007 <-- 01 August 2007

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Subject: Re: how to bring back the missing density for half of the structure
From: "Fan, Hai-fu" fanhf {- at -} CRYST {- dot -} IPHY {- dot -} AC {- dot -} CN
Date: 2007-08-01

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Subject: Re: how to bring back the missing density for half of the structure
From: Eleanor Dodson ccp4 {- at -} YSBL {- dot -} YORK {- dot -} AC {- dot -} UK
Date: 2007-08-01

Subject: difference density ripples around Hg atoms
From: Klemens Wild Klemens {- dot -} Wild {- at -} BZH {- dot -} UNI-HEIDELBERG {- dot -} DE
Date: 2007-08-01

Dear friends of the Fourier transform,

I am refining a structure with 2 adjacent Hg atoms bound to cysteines of
different monomers in the crystal contacts, which means I need to refine
them as well. While the structure nicely refines (2.2 A data), I do not
get rid of negative density ripple layers next to them (-10 sigmas). My
question: is this likely due to anistropy of the soft mercury atoms
(anisotropic B refinement decreases the ripples) or is this likely a
summation truncation effect prominent for heavy atoms? Can I just
anistropically refine the mercuries while I keep the rest isotropic?
Never saw this in a PDB. Suggestions are very welcome.

Greetings

Klemens Wild

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CCP4bb <-- 2007 <-- August 2007 <-- 01 August 2007

Previous message:
Subject: Re: how to bring back the missing density for half of the structure
From: "Fan, Hai-fu" fanhf {- at -} CRYST {- dot -} IPHY {- dot -} AC {- dot -} CN
Date: 2007-08-01

Next message:
Subject: Re: how to bring back the missing density for half of the structure
From: Eleanor Dodson ccp4 {- at -} YSBL {- dot -} YORK {- dot -} AC {- dot -} UK
Date: 2007-08-01