DNA Nanostructure Sequence-Dependent Binding of Organophosphates

understanding the molecular interactions between small molecules and double-stranded DNA has important implications on the design and development of DNA and DNA protein nanomaterials. Such materials can be assembled into a vast array of 1-, 2-, and 3D structures that contain a range of chemical and physical features where small molecules can bind via intercalation, groove binding, and electrostatics. In this work, we use a series of simulation-guided binding assays and spectroscopy techniques to investigate the binding of selected organophosphtates, methyl parathion, paraoxon, their common enzyme hydrolysis product pnitrophenol, and double-stranded DNA fragments and DNA DX tiles, a basic building block of DNA-based materials. Docking simulations suggested that the binding strength of each compound was DNA sequence-dependent, with dissociation Constants in the micromolar range. Microscale thermophoresis and fluorescence binding assays confirmed sequence-dependent binding and that paraoxon bound to DNA with Kd's between similar to 10 and 300 while methyl parathion bound with Kd's between similar to 10 and 100 mu M. p-Nitrophenol also bound to DNA but with affinities up to 650 mu M. Changes in biding affinity were due to changes in binding mode as revealed by circular dichroism spectroscopy. Based on these results, two DNA DX tiles were constructed and analyzed, revealing tighter binding to the studied compounds. Taken together, the results presented here add to our fundamental understanding of the molecular interactions of these compounds with biological materials and opens new possibilities in DNA-based sensors, DNA-based matrices for organophosphate extraction, and enzyme DNA technologies for organophosphate hydrolysis.