Hydrogen bonding in Watson-Crick base pairs.
AU pairs are base pairs between adenine and uracil. AU pairs are sometimes referred to as UA pairs when uracil occurs 5' of adenine.
AU pairs are weaker than GC pairs. Depending on their location in the RNA molecule, AU pairs are comparable to or stronger than GU pairs.
Lab submissions ideally contain between 30 and 50% AU pairs. Designs that contain excessive AU pairs, called cub scouts, are at increased risk of misfolding.