Photoisomerizable Guanosine Derivative as a Probe for DNA Base-Pairing in Langmuir Monolayers

Abstract

Mixtures of azo-functionalized amphiphilic derivatives of guanosine and of amphiphilic derivatives of other DNA nucleobases were deposited at an air–water interface and repeatedly irradiated with light of 340 and 440 nm wavelengths. The consequent switching between cis and trans configurations of the azobenzene moiety caused changes in the surface pressure of the film, which were analyzed using a model based on the two-dimensional Van der Waals equation of state. For mixed films of guanosine and cytidine derivatives, the analysis revealed a significant modification of the strength of intermolecular interaction caused by the optical irradiation, while no such modifications were identified in mixed films involving other nucleobases. The difference is attributed to light-induced breaking of the hydrogen bonding that is established only between specific nucleobases. The results demonstrate that photosensitive nucleoside derivatives can be used as an efficient probe for base-pairing in Langmuir monolayers.

The Past and the Future of Langmuir and Langmuir–Blodgett Films

“…Their binding constants and binding stoichiometry were quantified using elemental analysis by X-ray photoelectron spectroscopy (XPS) on the corresponding LB films. Molecular recognition of sugars, − nucleic acid bases, − amino acids, − peptides, − nucleotides, − and related molecules − was demonstrated, as illustrated in Figure . For example, hydrogen-bonding-based recognition of aqueous thymine derivatives by diaminotriazine-functionalized amphiphiles was confirmed at the air–water interface .…”

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

“…Therefore, they provide an attractive possibility that isomerization of the azobenzene group can be used to regulate their base pairing in various thin-film configurations. 81 This effect will be investigated in a separate study. However, the fraction of the molecules in the films that are switched upon irradiation is considerably smaller than the fraction of the molecules switched in solution.…”

“…The observed irradiation-induced changes in the absorption spectra of the films demonstrate that the investigated molecules can undergo a reversible photoisomerization both at the air–water interface and also after their LB deposition onto solid substrates. Therefore, they provide an attractive possibility that isomerization of the azobenzene group can be used to regulate their base pairing in various thin-film configurations . This effect will be investigated in a separate study.…”

“…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 − or into the water subphase. − In our recent study, we demonstrated that hydrogen bonding between guanosine and its complementary nucleoside (cytidine) at the air–water interface could be manipulated by optical irradiation . Besides the azobenzene moiety, guanosine molecules used in that study also possessed two hydrocarbon chains, which are generally believed to be necessary for the formation of molecular films at the water surface.…”

“… 70 − 80 In our recent study, we demonstrated that hydrogen bonding between guanosine and its complementary nucleoside (cytidine) at the air–water interface could be manipulated by optical irradiation. 81 Besides the azobenzene moiety, guanosine molecules used in that study also possessed two hydrocarbon chains, which are generally believed to be necessary for the formation of molecular films at the water surface. In this work, we report on the light-driven control of guanosine derivatives functionalized solely with the azobenzene moieties.…”