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Azobenzene-Substituted Triptycenes: Understanding the Exciton Coupling of Molecular Switches in Close Proximity.

ABSTRACT: Herein, we report a series of azobenzene-substituted triptycenes. In their design, these switching units were placed in close proximity, but electronically separated by a sp³ center. The azobenzene switches were prepared by Baeyer-Mills coupling as key step. The isomerization behavior was investigated by ¹ H NMR spectroscopy, UV/Vis spectroscopy, and HPLC. It was shown that all azobenzene moieties are efficiently switchable. Despite the geometric decoupling of the chromophores, computational studies revealed excitonic coupling effects between the individual azobenzene units depending on the connectivity pattern due to the different transition dipole moments of the π→π* excitations. Transition probabilities for those excitations are slightly altered, which is also revealed in their absorption spectra. These insights provide new design parameters for combining multiple photoswitches in one molecule, which have high potential as energy or information storage systems, or, among others, in molecular machines and supramolecular chemistry.

SUBMITTER: Kunz A

PROVIDER: S-EPMC9401047 | biostudies-literature | 2022 Jul

REPOSITORIES: biostudies-literature

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Azobenzene-Substituted Triptycenes: Understanding the Exciton Coupling of Molecular Switches in Close Proximity.

Kunz Anne A Oberhof Nils N Scherz Frederik F Martins Leon L Dreuw Andreas A Wegner Hermann A HA

Chemistry (Weinheim an der Bergstrasse, Germany) 20220603 38

Herein, we report a series of azobenzene-substituted triptycenes. In their design, these switching units were placed in close proximity, but electronically separated by a sp<sup>3</sup> center. The azobenzene switches were prepared by Baeyer-Mills coupling as key step. The isomerization behavior was investigated by <sup>1</sup> H NMR spectroscopy, UV/Vis spectroscopy, and HPLC. It was shown that all azobenzene moieties are efficiently switchable. Despite the geometric decoupling of the chromopho ...[more]

PMID: 35499252

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Project description:Background and purposeThe photo-isomerizable local anaesthetic, quaternary ammonium-azobenzene-quaternary ammonium (QAQ), provides rapid, optical control over pain signalling without involving genetic modification. In darkness or in green light, trans-QAQ blocks voltage-gated K+ and Na+ channels and silences action potentials in pain-sensing neurons. Upon photo-isomerization to cis with near UV light, QAQ blockade is rapidly relieved, restoring neuronal activity. However, the molecular mechanism of cis and trans QAQ blockade is not known. Moreover, the absorption spectrum of QAQ requires UV light for photo-control, precluding use deep inside neural tissue.Experimental approachElectrophysiology and molecular modelling were used to characterize the binding of cis and trans QAQ to voltage-gated K+ channels and to develop quaternary ammonium-ethylamine-azobenzene-quaternary ammonium (QENAQ), a red-shifted QAQ derivative controlled with visible light.Key resultstrans QAQ was sixfold more potent than cis QAQ, in blocking current through Shaker K+ channels. Both isomers were use-dependent, open channel blockers, binding from the cytoplasmic side, but only trans QAQ block was slightly voltage dependent. QENAQ also blocked native K+ and Na+ channels preferentially in the trans state. QENAQ was photo-isomerized to cis with blue light and spontaneously reverted to trans within seconds in darkness, enabling rapid photo-control of action potentials in sensory neurons.Conclusions and implicationsLight-switchable local anaesthetics provide a means to non-invasively photo-control pain signalling with high selectivity and fast kinetics. Understanding the mode of action of QAQ and related compounds will help to design of drugs with improved photo-pharmacological properties.Linked articlesThis article is part of a themed section on Recent Advances in Targeting Ion Channels to Treat Chronic Pain. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.12/issuetoc.

Project description:BackgroundAccording to Waddington's epigenetic landscape concept, the differentiation process can be illustrated by a cell akin to a ball rolling down from the top of a hill (proliferation state) and crossing furrows before stopping in basins or "attractor states" to reach its stable differentiated state. However, it is now clear that some committed cells can retain a certain degree of plasticity and reacquire phenotypical characteristics of a more pluripotent cell state. In line with this dynamic model, we have previously shown that differentiating cells (chicken erythrocytic progenitors (T2EC)) retain for 24 h the ability to self-renew when transferred back in self-renewal conditions. Despite those intriguing and promising results, the underlying molecular state of those "reverting" cells remains unexplored. The aim of the present study was therefore to molecularly characterize the T2EC reversion process by combining advanced statistical tools to make the most of single-cell transcriptomic data. For this purpose, T2EC, initially maintained in a self-renewal medium (0H), were induced to differentiate for 24H (24H differentiating cells); then, a part of these cells was transferred back to the self-renewal medium (48H reverting cells) and the other part was maintained in the differentiation medium for another 24H (48H differentiating cells). For each time point, cell transcriptomes were generated using scRT-qPCR and scRNAseq.ResultsOur results showed a strong overlap between 0H and 48H reverting cells when applying dimensional reduction. Moreover, the statistical comparison of cell distributions and differential expression analysis indicated no significant differences between these two cell groups. Interestingly, gene pattern distributions highlighted that, while 48H reverting cells have gene expression pattern more similar to 0H cells, they are not completely identical, which suggest that for some genes a longer delay may be required for the cells to fully recover. Finally, sparse PLS (sparse partial least square) analysis showed that only the expression of 3 genes discriminates 48H reverting and 0H cells.ConclusionsAltogether, we show that reverting cells return to an earlier molecular state almost identical to undifferentiated cells and demonstrate a previously undocumented physiological and molecular plasticity during the differentiation process, which most likely results from the dynamic behavior of the underlying molecular network.

Dataset Information

Azobenzene-Substituted Triptycenes: Understanding the Exciton Coupling of Molecular Switches in Close Proximity.

Publications

Azobenzene-Substituted Triptycenes: Understanding the Exciton Coupling of Molecular Switches in Close Proximity.

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