Abstract
Newly designed and synthesized diarylethene (DAE) derivatives with aliphatic amine sidearms and one with two pyrenes, revealed excellent photo-switching property of central DAE core in MeOH and water. The only exception was bis-pyrene analogue, its DAE core very readily photochemically closed, but reversible opening completely hampered by aromatic stacking interaction of pyrene(s) with cyclic DAE. In this process, pyrene fluorescence showed to be a reliable monitoring method, an open form characterized by strong emission at 480 nm (typical for pyrene-aggregate), while closed form emitted weakly at 400 nm (typical for pyrene-DAE quenching). Only open DAE-bis-pyrene form interacted measurably with ds-DNA/RNA by flexible insertion in polynucleotide grooves, while self-stacked closed form did not bind to DNA/RNA. For the same steric reasons, flexible open DAE-bis-pyrene form was bound to at least three different binding sites at bovine serum albumin (BSA), while rigid, self-stacked closed form interacted dominantly with only one BSA site. Preliminary screening of antiproliferative activity against human lung carcinoma cell line A549 revealed that all DAE-derivatives are non-toxic. However, bis-pyrene analogue efficiently entered cells and located in the cytoplasm, whereby irradiation by light (315–400 nm) resulted in a strong, photo-induced cytotoxic effect, typical for pyrene-related singlet oxygen species production.
Highlights
Low molecular weight photo-switch incorporated into DNA structure was able to control two single-stranded DNAs to reversibly intertwine into ds-DNA [22]
We described the synthesis of three novel diarylethene (DAE) photoswitches and fully characterized their spectroscopic and photochemical properties in MeOH and aqueous solution
[13] Intriguingly, photoinduced cyclisation kinetics of DAE showed to be concentration-dependent, for c(DAE-dye) > mM significantly slowing down, which was attributed to aromatic stacking interactions of DAE at such high concentrations: property not previously reported for DAE analogues
Summary
Synthetic small molecules targeting DNA, RNA or proteins by non-covalent interactions are of utmost scientific and biomedical interest [1], among which dyes attract attention because spectrophotometric probing is essential in the biomedical research [2,3], and due to theranostic applications by combining, e.g., fluorimetric probing with biological (therapeutic) activity [4,5]. In respect to DNA-controlled non-covalent binders, the pioneering work of Feringa et al showed how small molecule non-covalently bound to ds-DNA can upon photo-induced reversible chemical transformation influence DNA structure [13]. Low molecular weight photo-switch incorporated into DNA structure was able to control two single-stranded DNAs to reversibly intertwine into ds-DNA [22]
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