Beta pleated sheet parallel, antiparallel

The other structures that Pauling discovered by model-building are the j8-structures (pronounced beta), also known as the pleated sheet, from its appearance when many lengths of chain associate in parallel. They are formed by side-to-side association of almost fully extended chains, and the reason that two forms are possible is that adjacent chains may run in parallel or antiparallel (i.e. the same or opposite) directions, as shown here ... 

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