Stepwise electrochemical deposition and single-molecule conductance of nucleic acid analogues. (20th June 2020) - Elshahawy, Mohammad
Abstract: The stepwise synthesis of an electronically conducting, single strand DNA analogue is described. A gold electrode was first modified with a monolayer of 4-amino thiophenol, which acts as both a linker and polymerization initiation site. The electrode was then placed in a solution of an aniline-thymine monomer, tert-butyl N-{3-[2-(5-methyl-2, 4-dioxo-1, 2, 3, 4 tetrahydropyrimidin-1-yl) acetamido]phenyl} carbamate (t-BOC protected thymine aniline derivative). Applying a sufficiently positive potential triggers oxidative coupling, but, since the amine group of the incoming monomer is t-BOC protected, only a single monomer is added. The aniline amino group can then be deprotected and activated using trifluoroacetic acid to allow the next stepwise electro-addition of the aniline functionalized nucleic acid. In single-molecule STM measurements, the distance-dependent tunneling current for the aniline-thymine pentamer gives a conductance of 1.2 nS which is consistent with that observed for pure aniline oligomers. The molecular length of 2.7 ± 0.3 nm, as determined from the break-off distance, is in-line with structural modelling. While the principle is illustrated for up to ten cycles (10 mer formed) the approach allows the number of cycles and sequence of nucleic acids to be arbitrarily controlled within the electronically conducting DNA analogue.