Determination of DNA melting temperatures in diffusion-generated chemical gradients

For fast and reliable determination of DNA melting temperatures with single-nucleotide resolution in a microfluidic setup, stable gradients of the denaturing agent formamide were generated by means of diffusion. Formamide lowers the melting temperature of DNA, and a given formamide concentration can be mapped to a corresponding virtual temperature along the formamide gradient. We applied this concept to determine the melting temperatures of five sets of dye- and quencher-labeled oligonucleotides of different lengths. Differences in the length of complementary sequences of only one nucleotide as well as a single nucleotide mismatch can be detected with this method. Comparison with conventional melting temperature measurements based on temperature scans yields very good agreement.