Binding Kinetics of Bisintercalator Triostin a with Optical Tweezers Force Mechanics

The binding kinetics of the intercalative binding of Triostin A to lambda-DNA was investigated by measuring the force extension response of the DNA-ligand complexes with an optical tweezers system. These force response curves, containing the information about different binding properties, were analyzed based on a recent method (put forth by another research group) for monointercalators that was extended to bisintercalators. Our binding analysis reveals an exponential dependence of the association constant on the applied external force as well as a decreasing binding site size. In general, our results are in agreement with those for the monointercalator ethidium. However, to explain the high-force binding site size, a new model for bisintercalation of Triostin A at high forces is proposed.