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Re: [ccp4bb]: Mapstretch
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Mark van Raaij wrote:
>
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> Dear crystallographic colleagues,
> Is there a way to "stretch" maps equally in all three dimensions using
> ccp4, mapman or another tool? I have an averaged map from EM (brix, ccp4
> and xplor format) which is about 1.5 times too small to fit my
> crystallographic model into. I guess something went wrong in the
> calculation of the EM-magnification, but I don't know with which program
> that map was made.
> Before people attack me - I just want to make a nice picture with
> bobscript showing which part of the protein my partial model fits into.
> --
> Mark van Raaij, m.vanraaij@chem.leidenuniv.nl
We find this is essential before using EM images for molecular
replacement - it is worth stretching or shrinking them by small
fractions ( 1% ) then seeing which image gives the best signal.
I do it by hand - if you use maptona4 you get an ascii dump of the map,
and by altering the cell dimension by 1% you effectively shrink or
expand the image.
Then you can run maptona4 again to convert the file back to give a
modified map.
Here is script of sorts..
maptona4 mapin hao-thelot_mlp1.map mapout hao-thelot_mlp1.ascii
You need to half the cell dimensions: equivalent to scaling by 2
vi hao-thelot_mlp1.ascii
TITLE
Hand 1 mlp map
AXIS Z X Y
GRID 50 52 56
XYZLIM 0 49 0 51 0 55
SPACEGROUP 1
MODE 2
CELL 20.125 21.260 23.240 91.700 113.300 107.700
RHOLIM -1.33909 1.00938 -0.476994E-09 0.158896
INDXR4 0 22
END HEADER
SECTION 0
maptona4 mapout hao-thelot_mlp1_by_2.map mapin
hao-thelot_mlp1.ascii