In molecular biology, formamide (FA) is a commonly used denaturing agent for DNA. Although its influence on DNA duplex stability in solution is well established, little is known about immobilized DNA on microarrays. We measured thermal denaturation curves for oligonucleotides immobilized by two standard protocols: thiol self-assembling and pyrrole electrospotting. A decrease of the DNA denaturation temperature with increasing FA fraction of the solvent was observed on sequences with mutations for both surface chemistries. The average dissociation temperature decrease was found to be -0.58+/-0.05 degrees C/% FA (v/v) independently of grafting chemistry and probe sequence.
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