Tricky - perhaps this could be viewed as "anti-averaging" methodologically.
Use USF programs MAMA, IMP to generate a mask and optimize the NCS
operator (or skip this step if you feel you know yours accurately)
Use CCP4's MAPROT to rotate the map of one monomer onto the other
Conceivably use USF program COMDEM to create the "difference map"
assuming it will tolerate a weighting of -1. Or perhaps MAPROT will
take a negative scale. Or MAPMASK, or.... there's a range of map
manipulation programs that can scale an input map, but I've never tried
to invert one. Unless you actually wanted Fourier coefficients it
shouldn't be impossible to create a masked volume of the difference
between two maps after rotating one of them.
Phil Jeffrey
Princeton
On 3/10/17 5:24 PM, Oleg Zadvornyy wrote:
Dear All,
We are working on a tetrameric protein containing 2 heterodimers which
are related to each other by 2 fold symmetry. There are difference at
the active site between the two heterodimers in the crystals, and we
would like to make a difference map to compare one heterodimer to the
other. I would really appreciate your advise and suggestions how to
perform this comparison.
Thank you,
Oleg
--
Oleg A. Zadvornyy, PhD
Institute of Biological Chemistry,
Washington State University
237 Clark Hall
Pullman, WA 99163
Tel: (509)-335-9837
Lab: (509)-335-1958
