[phenixbb] Stretched Maps

Nathaniel Echols nechols at lbl.gov
Wed Oct 20 12:03:53 PDT 2010


On Wed, Oct 20, 2010 at 11:58 AM, Joel Weadge <joelweadge at hotmail.com> wrote:
> I have just finished doing molecular replacement and an initial round of
> refinement (with simulated annealing) on a number of different datasets.
> They have all be straightforward since most of them are either point mutants
> and/or co-crystal structures. However, two of the structures are giving me
> some trouble. The data appears to be of good quality and resolution (2.25
> and 2.55Å). The MR proceeds as normal with good scores and then in the
> subsequent round of refinement the maps (2Fo-Fc and Fo-Fc) look strange. The
> density is stretched or flattened in one direction. Can anyone help me with
> what I may be overlooking?

Since our list server rejected Joel's Coot screen capture, I've posted it here:

http://cci.lbl.gov/~nat/img/stretched.png

My semi-informed guess would be either severe anisotropy or systematic
incompleteness (i.e. didn't collect enough degrees).

-Nat



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