Trapping of DNA by thermophoretic depletion and convection.

188103-1 Thermophoresis depletes DNA from a heated spot. We quantify for the first time the thermal diffusion constant DT 0:4 10 8 cm2=sK for DNA, using fluorescent dyes and laser heating. For 5 kB DNA we extrapolate a 1000-fold depletion from a temperature difference of 50 K. Surprisingly, convection generated by the same heating can turn the depletion into trapping of DNA. Trapped DNA can form point geometries 20 m in diameter with more than 1000-fold enhanced concentrations. The accumulation is driven only by temperature gradients and offers a new approach to biological microfluidics and replicating systems in prebiotic evolution.