The effects of mismatches on hybridization in DNA microarrays: determination of nearest neighbor parameters. synthetic construct

Quantifying interactions in DNA microarrays is of central importance for a better understanding of their functioning. Hybridization thermodynamics for nucleic acid strands in aqueous solution can be described by the so-called nearest-neighbor model, which estimates the hybridization free energy of a given sequence as a sum of dinucleotide terms. Compared with its solution counterparts, hybridization in DNA microarrays may be hindered due to the presence of a solid surface and of a high density of DNA strands. We present here a study aimed at the determination of hybridization free energies in DNA microarrays. Experiments are performed on custom Agilent slides. The solution contains a single oligonucleotide. The microarray contains spots with a perfect matching complementary sequence and other spots with one or two mismatches: in total 1006 different probe spots, each replicated 15 times per microarray. The free energy parameters are directly fitted from microarray data. The experiments demonstrate a clear correlation between hybridization free energies in the microarray and in solution. The experiments are fully consistent with the Langmuir model at low intensities, but show a clear deviation at intermediate (non-saturating) intensities. These results provide new interesting insights for the quantification of molecular interactions in DNA microarrays. Keywords: experiment to assess technical aspects of hybridization in microarrays Overall design: The study consists of four experiments. Each experiments consists of one slide with eight identical microarrays which were hybridized with an identical solution but at a different concentration. Per experiment a single target sequence in solution was used for hybridization: target1 to target4 (Table 1 main manuscript or description of samples below). Each target oligo was bought in duplicate, referred to as oligos a and b. In experiment 1 and 2 a fragmentation step (f) was applied. More details can be found in the main manuscript especially Table 3.