Visible‐Light Photoresponsivity of a 4‐(Dimethylamino)azobenzene Unit Incorporated into Single‐Stranded DNA: Demonstration of a Large Spectral Change Accompanying Isomerization in DMSO and Detection of Rapid (<i>Z</i>)‐to‐(<i>E</i>) Isomerization in Aqueous Solution

Abstract

Abstract We demonstrate significant visible‐light photoresponsivity in a synthesized oligonucleotide containing a built‐in pseudo‐nucleotide possessing a 4‐(dimethylamino)azobenzene (4‐DMAzo) side chain. In dry DMSO as solvent, two clearly distinguishable spectra corresponding to the ( E ) and ( Z ) forms of the 4‐DMAzo moiety tethered to the oligonucleotide were recorded with a conventional spectrophotometer before and after irradiation with 420 nm wavelength light, which induced ( E )‐to‐( Z ) isomerization. In addition, ( Z )‐to‐( E ) isomerization was accelerated by irradiation with either visible ( λ = 550 nm) or UV ( λ = 350 nm) light, demonstrating reversible photoresponsivity of the pseudo‐oligonucleotide. In aqueous solutions the ( Z )‐to‐( E ) thermal isomerization of the photoresponsive pseudo‐oligonucleotide was very rapid and was only detectable by laser flash photolysis.(© Wiley‐VCH Verlag GmbH &amp; Co. KGaA, 69451 Weinheim, Germany, 2007)