Reversible Photoisomerization in Thin Surface Films from Azo-Functionalized Guanosine Derivatives.

Matjaž Ličen,Silvia Pieraccini,Irena Drevenšek-Olenik,Stefano Masiero

doi:10.1021/acsomega.1c01879

Abstract

Two novel azo-functionalized guanosine derivatives were synthesized, and their photoisomerization process was investigated in molecular monolayers at the air–water interface and in the Langmuir–Blodgett (LB) films on solid substrates. Measurements of surface pressure vs area isotherms, surface potential measurements, UV–visible (vis) absorption spectroscopy, Brewster angle microscopy (BAM), and atomic force microscopy (AFM) were performed. Despite not having a typical amphiphilic molecular structure, the derivatives formed stable films on the water surface. They could also undergo repeated photoisomerization in all of the investigated thin-film configurations. The observations suggest that in the films at the air–water interface, the molecules first exhibit a conformational change, and then they reorient to an energetically more favored orientation. In the LB films transferred onto solid substrates, the isomerization process occurs on a similar time scale as in solution. However, the isomerization efficiency is about an order of magnitude lower than that in solution. Our results show that DNA nucleobases functionalized with azobenzene moieties are suitable candidates for the fabrication of photoactive two-dimensional (2D) materials that can provide all beneficial functionalities of DNA-based compounds.

Highlights

Because of their versatility and many appealing structural and physical properties, DNA and its components and their derivatives are emerging candidates for use in a wide range of applications, from memory devices,[1,2] various self-assembled nanostructures,[3−12] molecular computing units,[13−21] and nanosensors[22−27] to biocompatible electronics.[28−41] Among the four DNA nucleobases, guanosine stands out due to its ability to form stable and robust noncanonical structures with other guanosine molecules, in particular G-quadruplexes
It is known that base pairing can take place in the Langmuir film of a selected nucleoside when its complementary nucleobase is introduced either to the air−water interface[66−69] or into the water subphase.[70−80] In our recent study, we demonstrated that hydrogen bonding between guanosine and Received: April 8, 2021
The surface pressure vs area isotherms measured in five consecutive compression−expansion cycles of the GAzo and GAzo[3] Langmuir films and the Brewster angle microscopy (BAM)

Summary

INTRODUCTION

Because of their versatility and many appealing structural and physical properties, DNA and its components and their derivatives are emerging candidates for use in a wide range of applications, from memory devices,[1,2] various self-assembled nanostructures,[3−12] molecular computing units,[13−21] and nanosensors[22−27] to biocompatible electronics.[28−41] Among the four DNA nucleobases, guanosine stands out due to its ability to form stable and robust noncanonical structures with other guanosine molecules, in particular G-quadruplexes. Among different methods for controlling hydrogen bonding,[53] lightdriven control is often favored because it is noninvasive and offers precise spatial and temporal regulation Such a control can be implemented by modification of a nucleobase with a photoactive moiety so that its binding to other nucleobases can be regulated by irradiation with light of a specific wavelength.[54−56] The most common of such moieties are azobenzene derivatives. The results show that these very simple derivatives form stable Langmuir and LB films whose configurational state can be repeatedly switched by optical irradiation

EXPERIMENTAL RESULTS

DISCUSSION AND CONCLUSIONS

MATERIALS AND METHODS

■ ACKNOWLEDGMENTS

■ REFERENCES

Brewster Angle Microscopy and Atomic Force