Effect of Ectoine on the Conformation and Hybridization of dsDNA in Monolayer Films: A Spectroelectrochemical Study

Abstract

Lack of long-time stability of dsDNA-based supramolecular assemblies is an important issue that hinders their applications. In this work, 20 base pairs long dsDNA fragments [(dCdG) 20 -65 %] composed of 65 % dCdG and 35 % dAdT nucleotides were tethered via a thiol to the surface of a gold electrode. The selfassembled (dCdG) 20 -65 % monolayer was immersed in solutions containing ectoine, a compatible solute. Electrochemical results showed that these monolayers were stable for one month. In situ IR spectroscopy indicated that ectoine interacts weakly with the phosphate-ribose backbone, dehydrating the phosphate groups and stabilizing the A-DNA conformation. This structural reorganization led to a reorientation of nucleic acid base pairs and a local disruption of the double-helix structure. However, the conformation and orientation of the dsDNA fragment was stable in the À 0.4 < E < 0.3 potential range. As a direct interaction between ectoine and dsDNA, the enzymatic reaction of exonuclease VII hydrolyzing the ester phosphate bond in ssDNA, was blocked. We show that the addition of a compatible solute to the electrolyte solution stabilized the dsDNA structure despite structural rearrangements.