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Re: [ccp4bb]: Cys modification

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On Mon, 17 Apr 2000, Manfred Buehner wrote:
> On Mon, 17 Apr 2000, Jeff Taylor wrote:
> > I've also been wondering about extra density
> Magnesium is not probable since it makes a lousy sulfide, How about
> zink?

Zinc has an absorption edge at 1.28 A, so should show up well in anomalous
difference Fourier maps collected at typical synchrotron wavelengths. I
see Zn in one of my structures and it shows up quite well at 1.08 A (SSRL
beamline 7-1) as compared with in-house Cu Kalpha (1.54 A). In my case it
shows up around carboxylic acids, but then all my Cys residues are tied up
in disulfides.

also, if this extra density is on the surface of your molecule, be aware
that what looks like multiple atoms may be multiple conformations.

"We are going to die, and that makes us the lucky ones" - Richard Dawkins
                        David J. Schuller
                        modern man in a post-modern world
                        University of California-Irvine