perhaps they are Cl-, K+, Ca2+ or some other heavier thing?
Mg2+ only has the same amount of electrons as a water molecule.
Mark J van Raaij
Dpto de Estructura de Macromoleculas
Centro Nacional de Biotecnologia - CSIC
c/Darwin 3
E-28049 Madrid, Spain
tel. (+34) 91 585 4616
http://wwwuser.cnb.csic.es/~mjvanraaij
> On 4 Aug 2016, at 16:00, Almudena Ponce Salvatierra <[log in to unmask]> wrote:
>
> Dear all,
>
> I am refining a structure that showed two positive peaks larger than 8 sigma. I assigned them as Mg ions, since I have them in the crystallization condition and also because it make sense, according to where they are located.
>
> However when I refine there's still all this green blob around the already properly placed Mg ions. I don't know why, they don't show large thermal factors or anything suspicious...
>
> I'm refining individual sites, individual adps, and TLS groups.
>
> The resolution I am talking about is 2.5 A.
>
> Any thoughts on this?
>
> Thank you very much
>
> Best wishes,
>
> Almudena
> --
> Almudena Ponce-Salvatierra
> Macromolecular crystallography and Nucleic acid chemistry
> Max Planck Institute for Biophysical Chemistry
> Am Fassberg 11 37077 Göttingen
> Germany
>
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