Temperature dependence of DNA elasticity and cisplatin activity studied with a temperature-controlled magnetic tweezers system

Understanding the elastic property of DNA is one of the most fundamental issues in DNA science. The elastic property of DNA has been much studied at a single molecule level by using various micromanipulation tools, but its temperature dependence has only been studied in a limited range of temperatures. Here, we report our results regarding the elastic property of a single DNA molecule at high temperature. In order to accomplish that, we designed a simple ITO-based temperature-control system with which the temperature of the sample chamber in magnetic tweezers could be tuned up to 90 °C. Soft silicone tubing that circulates water at a certain preset temperature was wound around the objective, a dominant heat sink in the system. For temperatures beyond 50 °C, the DNA molecule appeared longer than its original length, presumably due to thermal melting of DNA, while its persistence length (ξ) was gradually decreased. In addition, we found that the activity of cisplatin (DNA-binding anti-cancer drug) on DNA was enhanced at high temperatures, resulting in more efficient DNA condensation.