One Cohesive End Ligation Unit is defined as the amount of
enzyme required to give 50% ligation of Hind III digested λ
DNA in 30 minutes at 16°C in 20 μl at a 5´ termini concentration
of 0.12 μM (300 μg/ml).
One Cohesive End Ligation Unit equals 0.015 Weiss (ATP-PP
exchange) units (4). Equivalently, one Weiss unit equals 67
Cohesive End Ligation Units.