The document SheetBridges.pdf has been placed on the website
http://homepage.mac.com/whitby/
It shows the assembly of sheet bridges and how they function in the
formation of the pleated sheet. The bridges, which connect the strands
of a pleated sheet, permit intervening strands to pass under or over.
A one strand bridge contains just four main chain units. Its span can
be extended to permit 6, 11, 16, ... sheet joined strands to pass
unimpeded. A sheet consisting of four pairs of parallel strands
arranged so that adjacent pairs are anti-parallel is shown. The bridge
arrangement for this eight strand sheet is depicted schematically.
