Light-Induced Modulation of Chiral Functions in G-Quadruplex–Photochrome Systems

Abstract

The design of artificially engineered chiral structures has received much attention, but the implementation of dynamic functions to modulate the chiroptical response of the systems is less explored. Here, we present a light-responsive G-quadruplex (G4)-based assembly in which chirality enrichment is induced, tuned, and fueled by molecular switches. In particular, the mirror-image dependence on photoactivated azo molecules, undergoing trans -to- cis isomerization, shows chiral recognition effects on the inherent flexibility and conformational diversity of DNA G4s having distinct handedness (right- and left-handed). Through a detailed experimental and computational analysis, we bring compelling evidence on the binding mode of the photochromes on G4s, and we rationalize the origin of the chirality effect that is associated with the complexation event.

Linear and Nonlinear Optical Properties of Azobenzene Derivatives Modified with an (Amino)naphthalene Moiety

“… 18 The physicochemical and structural changes accompanying their E – Z photoisomerization, i.e., the photochromic effect, have been widely exploited to provide the strategy for material modification by means of light stimulation. 19 , 20 Up to now, azo compounds have been used to modulate the properties of supramolecular systems, 21 − 23 biomolecules (DNA, protein), 24 , 25 ion channels and receptors, 26 , 27 polymers, 28 and liquid crystals, 29 , 30 in solution as well as on surfaces and bulk materials, transferring effects from the molecular level to the macroscopic scale. 31 In general, the E – Z isomerization is induced by UV irradiation and the return to the initial state can be achieved either by visible light or thermally.…”

“…The interest in development of molecular switches − arises from the fact that imparting external sensitivity to molecular systems is an efficient way to control on-demand their structure, properties, and functions and hence offers multiple applications in materials − and biological sciences. − Among various external triggers, light is the most desired kind of stimulus, because spatiotemporal resolution, excitation tunability, and biocompatibility are achieved through remote control. ,, A particularly important group of light-sensitive compounds in this context are azobenzenes (ABs) . The physicochemical and structural changes accompanying their E – Z photoisomerization, i.e., the photochromic effect, have been widely exploited to provide the strategy for material modification by means of light stimulation. , Up to now, azo compounds have been used to modulate the properties of supramolecular systems, − biomolecules (DNA, protein), , ion channels and receptors, , polymers, and liquid crystals, , in solution as well as on surfaces and bulk materials, transferring effects from the molecular level to the macroscopic scale . In general, the E – Z isomerization is induced by UV irradiation and the return to the initial state can be achieved either by visible light or thermally. , However, especially in biology, due to limitations concerning one-photon excitation such as light penetration depth or toxicity of UV light, the two-photon (2P) excitation of the photochromic molecules may appear useful. , The longer excitation wavelengths provide deeper and safer tissue penetration in comparison to that of the conventional linear (one-photon) absorption species.…”

Parallel G-Quadruplex DNA Structures from Nuclear and Mitochondrial Genomes Trigger Emission Enhancement in a Nonfluorescent Nano-aggregated Fluorine–Boron-Based Dye

“… 1 In particular, noncanonical four-stranded DNA structures such as intercalated motifs (i-DNAs) and G4s have received increasing scientific attention, not only for being implicated in key biological processes, 2 − 4 but also for their predictable and controllable properties. Indeed, such structures can afford complex nanometer scale systems suited for molecular computing, 5 , 6 transport, 7 , 8 amplification of chirality, 9 and biosensing 10 − 17 applications. While i-DNAs are predominantly formed under acidic conditions (pH < 7), 18 − 20 G4s are thermodynamically stable at physiological pH.…”

“…In particular, noncanonical four-stranded DNA structures such as intercalated motifs (i-DNAs) and G4s have received increasing scientific attention, not only for being implicated in key biological processes, − but also for their predictable and controllable properties. Indeed, such structures can afford complex nanometer scale systems suited for molecular computing, , transport, , amplification of chirality, and biosensing − applications. While i-DNAs are predominantly formed under acidic conditions (pH < 7), − G4s are thermodynamically stable at physiological pH. , G4s are composed of stacked G-tetrads octa-coordinated by a central metal ion (usually K + ) and further stabilized by intraquartet hydrogen bonds. , Owing to their polynucleotide constitution and dynamic conformation, G4s show high polymorphism in solution.…”