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Herein we demonstrate the synthesis of a helicene-based imidazolium salt. The salt was prepared by starting from racemic 2-methyl[6]helicene, which undergoes radical bromination to yield 2-(bromomethyl)[6]helicene. Subsequent treatment with 1-butylimidazole leads to the corresponding salt 1-butyl-3-(2-methyl[6]helicenyl)-imidazolium bromide. The prepared salt was subsequently characterized by using NMR spectroscopy and X-ray analysis, various optical spectrometric techniques, and computational chemistry tools. Finally, the imidazolium salt was immobilized onto a SiO2 substrate as a crystalline or amorphous deposit. The deposited layers were used for the development of organic molecular semiconductor devices and the construction of a fully reversible humidity sensor.

The quaternary isoquinoline alkaloid, sanguinarine (SG) plays an important role in both traditional and modern medicine, exhibiting a wide range of biological activities. Under physiological conditions, there is an equilibrium between the quaternary cation (SG+) and a pseudobase (SGOH) forms of SG. In the gastrointestinal tract, SG is converted to dihydrosanguinarine (DHSG). All forms exhibit bright fluorescence. However, their spectra overlap, which limited the use of powerful techniques based on fluorescence spectroscopy/microscopy. Our experiments using a combination of steady-state and time-resolved techniques enabled the separation of individual components. The results revealed that (a) the equilibrium constant between SG+ and SGOH is pKa = 8.06, while fluorescence of DHSG exhibited no changes in the pH range 5-12, (b) the SGOH has excitation/emission spectra with maxima at 327/418 nm and excited-state lifetime 3.2 ns, the spectra of the SG+ have maxima at 475/590 nm and excited-state lifetime 2.4 ns. The DHSG spectra have maxima at 327/446 nm and 2-exponential decay with components 4.2 and 2.0 ns, (c) NADH is able to convert SG to DHSG, while there is no apparent interaction between NADH and DHSG. These techniques are applicable for monitoring the SG to DHSG conversion in hepatocytes.

Electrochemistry of membrane proteins is complicated by the fact that the studied substances are poorly soluble or insoluble in aqueous environment. The solubilization of proteins using surfactants (detergents) affects the electrochemical analysis or even renders it impossible. In the present study, the electrochemistry of the transmembrane protein Na+/K+‐ATPase (NKA) and its water‐soluble isolated cytoplasmic loop C45 is described. The proteins were studied using adsorptive transfer cyclic voltammetry and square‐wave voltammetry on basal‐plane pyrolytic graphite electrode (PGE) as well as constant‐current chronopotentiometric stripping analysis on hanging mercury drop electrode (HMDE). The nonionic surfactant octaethylene glycol monododecyl ether (C12E8) was used for NKA solubilization. Under these conditions the oxidation currents of Tyr and Trp (peak Y: +0.55 V and peak W: +0.7 V, vs. Ag/AgCl/3 M KCl) and catalytic reduction currents (peak H: −1.8 V) of NKA and C45 loop can be observed. Using the experimental procedures suggested in this study, we were able to investigate the oxidation, reduction and adsorption of NKA and C45 at femtomole level without the necessity of labeling by electroactive markers or techniques based on protein immobilization within the lipid bilayer attached to the electrode surface.