How to generate different resolution .mrc map from PDB structure by e2pdb2mrc.py

[张海平]

Hi eman2 user:

I want to generate different resolution  .mrc map from PDB structure by e2pdb2mrc.py, but when I used following command with different resolution set e.g. 20,100 , the resolutions of generated map seems haven't change at all. I don't know why. If I want to generate a real 20 or 100 resolution .mrc map from pdb structure, what kinds of command should I used? Do I need to change apix value accordingly? Thanks a lot.

e2pdb2mrc.py name.pdb name.mrc apix=1 res=20 center

e2pdb2mrc.py name.pdb name.mrc apix=1 res=100 center​

outcome of these two command seems totally same.

best regards

[Steven Ludtke]

You are missing the '--' in front of the options. 

e2pdb2mrc.py name.pdb name.hdf --apix=1 --res=20 --center

Note that this produces maps with specified "resolvabilities" not "resolutions" per-se. In Cryo-EM and to an extent, X-ray crystallography, "resolution" is a measure of signal-to-noise ratio, not how blurry the map is.  The amount of blurring is the "resolvability" and is a somewhat independent property.

To be clearer, if you had a 10 Å resolution map, and you low-pass filtered it to 15 Å (using a Gaussian or other low-pass filter that doesn't go to zero) it is still a 10 Å resolution map, and could be resharpened to recreate the sharper features.

e2pdb2mrc.py does not add any noise to the resulting maps, it only low-pass filters them, using a Gaussian filter. So in reality high resolution information is still present, just damped.

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