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Re: [ccp4bb] difference density ripples around Hg atoms |
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CCP4bb navigationCCP4bb <-- 2007 <-- August 2007 <-- 01 August 2007Subject: Re: difference density ripples around Hg atoms From: Kevin Jude kjude {- at -} BERKELEY {- dot -} EDU Date: 2007-08-01 sigma peak for Hg is not that surprising! Anisotropic refinement was not helpful in reducing the ripples, as it is indeed a summation problem. It's a good idea to refine occupancy of the Hg, though, and to look for dual conformations of the cysteines. best wishes kmj Klemens Wild wrote: > 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 CCP4bb navigationCCP4bb <-- 2007 <-- August 2007 <-- 01 August 2007 |
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