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RE: [ccp4bb]: STructure question!



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Here is a upper/lower/sloppy case estimate:

> > If I have a 9 residue peptide, what is the farthest distance
> > between the 
> > C-alpha atoms of the 1st and 9th residue. I know that ca-ca 
> > is 3.8A.  But I am not sure if it is 3.8x9 or is it different 
> > - can it be longer?
> 
 8 times only:
 
 *-1-*-2-*-3-*-4-*-5-*-6-*-7-*-8-*

 9 stars...

  Then: extended maximally considering no gyration around 
phi/psi ignoring steric restriction gives about 28A 
(pulling hard, so to speak) ~ (n/2)*(3.8*cos(30)+3.8)
(would look bad in ramachandran plot with one cluster
of overlying verbotens..., the so called torture case by ED)

for helix you know 3.6 residues/turn and rise of 5.4
- > low estimate 12A.
 
Free gyration is around 18-22 I wager.
 
Best, br
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