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A coupling motif formed by the two arms extending out from the parallel duplexes, to form a long column of anti-parallel duplexes (A) and a large channel extending along the c-axis, presumably occupied by water (B). The crystallographic 2-fold axes are indicated with an arrow and a cross. The parallel duplex regions protrude from the column like knobs at right angles. The flat end of each parallel duplex is stacked with another flat end of the adjacent parallel duplex.
