Questions about barrels

1. How to calculate axis of a barrel? (if we have the axis, maybe it will help us to calculate the bended strand)

2. Any other methods to calculate the bended angle which doesn't need pdbsum info?

• maybe I'll use this method to calculate the angle of the planes of ribbon in one strand, so that we can calculate the bended angle. (Because the method which calculates the angle between residues seems doesn't work)

3. why 1p3hA is n*=4, S*=8? it seems to me it's S should be more then 8.