Isolating Ligands from Ribosome Reconstructions
Differences between volumes can be assessed by subtracting one
volume from the other; the result is a difference map.
Such differences provide one way to identify or isolate small masses
in 3D reconstructions. The
statistics of the volumes may be used to determine the significance
of 3-dimensional features (see pages 252-254 in
Three-Dimensional Electron Microscopy of Macromolecular
Assemblies by J. Frank).
Before subtracting volumes, make sure they are properly aligned.
- Check alignment of two volumes.
PK 3 to determine if volumes
are shifted relative to each other.
- Ligands can be isolated by creating a difference map.
computes difference bewteen two volumes.
- Alternatively, the SPIDER operation
computes the error and difference
between two volumes.
- For display and illustration purposes, this
recipe of interactive
operations in may be entered in SPIDER to extract and
isolate a mass from a volume:
Page updated: 09/15/06