[3dem] Voxel Values (Scaling and Units) in cryoEM

[Benjamin Barad]

Hi everyone,

I wonder whether someone could comment on why the numeric voxel values of
maps in the EMDB (or elsewhere) have such large differences in their range.
Do the absolute values have physical meaning, and if so how should I
interpret the vast ranges in scale? What units should be ascribed to them?

Even if they are not physically meaningful, why is there such a dramatic
range in scaling?

For some examples, the map parameters for EMDB 5623 are as follows:
Minimum density:-0.555
Maximum density:1.20
Average density:-0.008
Standard deviation:0.049
Recommended contour level:0.25 (author)







By comparison, the map parameters for EMDB 2278 are:
Minimum density:-9.453
Maximum density:15.384
Average density:0.048
Standard deviation:1.252
Recommended contour level:1.35 (emdb)







And the map parameters for EMDB 6324 are:
Minimum density:-0.092
Maximum density:0.139
Average density:0.001
Standard deviation:0.005
Recommended contour level:0.016 (emdb)








Thanks,
Ben Barad
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