This is a beta-pleated sheet in which adjacent beta strands in the structure point in opposite directions, for example amino-terminal to carboxy-terminal, carboxy-terminal to amino-terminal, amino-terminal to carboxy-terminal, etc. Such sheets have narrowly spaced hydrogen bond pairs that alternate with widely spaced pairs. In each residue the main chain -NH and -CO groups point in the same direction, but which alternates with successive residues.