trans-AzoTAB

trans-AzoTAB is a photoresponsive potassium/sodium/calcium channel modulator and DNA-binding agent. trans-AzoTAB undergoes trans-cis isomerization driven by light, with variable polarity and DNA affinity. trans-AzoTAB also enhances voltage-gated potassium currents and inhibits sodium and calcium currents in cardiomyocytes, thereby reducing spontaneous electrical activity and excitation conduction velocity. In addition, trans-AzoTAB induces compaction and frozen conformation of λ-phage DNA, and non-sequence-dependently inhibits transcription and translation processes in the dark; its activity can be reversed and restored by visible light after activation with ultraviolet irradiation. trans-AzoTAB can serve as a probe for two-photon optical regulation of myocardial excitability, and is used to construct photoresponsive interfacial polymer structures ^{[1] [2] [3] [4]}.

In Vitro, Trans-AzoTAB (1-100 μM; ≥3 min) inhibits voltage-gated peak sodium currents in isolated neonatal rat ventricular myocytes in a concentration-dependent manner, with an EC50 of 60 μM, and reduces the current density by approximately 60% at 100 μM^[1]. Trans-AzoTAB (100 μM; ≥3 min) inhibits L-type voltage-gated calcium currents in isolated neonatal rat ventricular myocytes by approximately 60%, and this inhibitory effect is reversible via near-ultraviolet light-induced isomerization of Trans-AzoTAB to cis-AzoTAB^[1]. Trans-AzoTAB (100 μM; ≥3 min) increases the voltage-gated steady-state potassium current in isolated neonatal rat ventricular myocytes to approximately 145% of the control level, and this enhancing effect is reversible via near-ultraviolet light-induced isomerization of Trans-AzoTAB to cis-AzoTAB^[1]. trans-AzoTAB (0.0-2.0 mM) induces end-grafted λ-phage DNA to form a frozen surface-adsorbed conformation at concentrations ≥0.3 mM; its lateral extension continuously increases before reaching the freezing threshold, remains stable in the intermediate concentration range, and decreases at concentrations ≥0.8 mM^[2]. trans-AzoTAB (0.0-3.0 mM; 20 min) reversibly regulates the transcriptional activity of T4 genomic DNA with *E. coli* RNA polymerase and DNA conformation in a light-dependent manner; under dark conditions, it completely inhibits transcription at concentrations ≥2.0 mM, and up to 80% of the activity can be restored after 10 min of irradiation with 365 nm ultraviolet light^[3]. trans-AzoTAB (0.0-3.0 mM; 20 min) enables reversible regulation of the transcriptional activity of a 5 kb linearized plasmid carrying T7 RNA polymerase via light; transcriptional activity is completely inhibited at concentrations ≥2.0 mM under dark conditions, and after 10 min of irradiation with 365 nm ultraviolet light, transcriptional activity recovers to exceed the control level without altering the nature of the transcript^[3].

References:
[1]. Frolova SR, et al. Photocontrol of Voltage-Gated Ion Channel Activity by Azobenzene Trimethylammonium Bromide in Neonatal Rat Cardiomyocytes. PLoS One. 2016;11(3):e0152018. Published 2016 Mar 25.
[2]. Sun Y L, et al. Photocontrol of end-grafted lambda-phage DNA[J]. Soft Matter, 2011, 7(12): 5578-5584.
[3]. Estévez-Torres A, et al. Sequence-independent and reversible photocontrol of transcription/expression systems using a photosensitive nucleic acid binder. Proc Natl Acad Sci U S A. 2009;106(30):12219-12223.
[4]. Shcherbakov D, et al. Optical control of cardiac cell excitability based on two-photon infrared absorption of AzoTAB[J]. arXiv preprint arXiv:1401.0346, 2014.