One hundred-fold acceleration of DNA renaturation rates in solution

Solvents which accelerate DNA renaturation rates have been investigated. Addition of NaCl or LiCl to DNA in 2.4M Et₄NCl initially increases renaturation rates at 45°C and then leads to a loss of second-order behavior. The greatest accelerations are seen with LiCl and dilute DNA. Volume exclusion by dextran sulfate is the most effective method of accelerating DNA renaturation with concentrated DNA. Addition of dextran sulfate beyond 10-12% in 2.4M Et₄NCl fails to increase the acceleration beyond approximately 10-fold. Accelerations of 100-fold may be achieved with 35-40% dextran sulfate in 1M NaCl at 70°C. No other mixed solvent system was found to be more effective, although acceleration may be achieved in solvents containing formamide or other denaturants. The acceleration in 2M NaCl occurs without loss of the normal concentration and temperature dependence of DNA renaturation and is also independent of dextran sulfate concentration if sufficient dextran sulfate is used. Dextran sulfate may be selectively precipitated by use of 1M CsCl.