Antiparallel (biochemistry)

An example is the two complementary strands of a DNA double helix, which run in opposite directions alongside each other.

The nucleic acid sequences are complementary and parallel, but they go in opposite directions, hence the antiparallel designation.

The importance of an antiparallel DNA double helix structure is because of its hydrogen bonding between the complementary nitrogenous base pairs.

In beta sheets, sections of a single polypeptide may run side-by-side and antiparallel to each other, to allow for hydrogen bonding between their backbone chains.

However, an anti-parallel beta sheet is significantly more stable than a parallel structure due to their well aligned H-bonds, which are at a 90° angle.