Macromolecular crowding accelerates the cohesion of DNA fragments with complementary termini

Macromolecular crowding increases the rate of nonenzymatic cohesion of the complementary ends of lambda DNA. Both lambda DNA and DNA fragments bearing the cohesive ends of lambda DNA are similarly affected. High concentrations of plasma albumin or Ficoll 70 increase the rate of cohesion by ca. 100-fold whereas high concentrations of polyethylene glycol 8000 cause greater than 2000-fold stimulation in this rate. These results have implications for the mechanism of polymer-stimulated enzymatic ligation of DNA or RNA. In addition, these crowding effects may help to explain the rapid cohesion of lambda DNA observed in vivo. An improved procedure for the recovery of DNA fragments separated by agarose gel electrophoresis is also described.