Anisotropy of the molecular inertial ellipsoid in PDB
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We all know that protein molecules are "little balls" (globules). How
good this approximation is? It is possible that some protein molecules
(globules) are elongated or flattened? We cat describe the deviation
of the shape from the ideal sphere by exploring ellipsoid of inertia
of a protein molecule. (https://en.wikipedia.org/wiki/Moment_of_inertia,
https://en.wikipedia.org/wiki/Moment_of_inertia#Ellipsoid).

Questions:

- Examine the entire PDB - how much do molecules deviate from an ideal
  sphere?  Which are "flattened" and which are "stretched"? What
  parameters are the best to describe these deviations?

- What are the parameters distributions describing the "sphericity" of
  protein molecules? What are typical or atypical parameters values?
  In what molecules are they found?

- Is the ellipsoid shape representative for the entire molecule? Maybe
  better calculate ellipsoids for each domain, or for each chain? How
  to get information about the domains of a molecule ?

- Can we see the biological or physical reason of "non-sphericity" of
  protein molecules?

Program:

This research requires a program that reads PDB archive files and
determines and outputs values of the components of the inertia tensor
for each chain (each domain?). Think how to make these values
comparable for different proteins, i.e. calculate quantities that do
not depend on coordinates systems. Think about how to classify
according to these values molecules into 'spherical', 'flattened' and
'elongated' or some other way.