A blue-shifted anion channelrhodopsin from the Colpodellida alga Vitrella brassicaformis.

Microbial rhodopsins, a family of photoreceptive membrane proteins containing the chromophore retinal, show a variety of light-dependent molecular functions. Channelrhodopsins work as light-gated ion channels and are widely utilized for optogenetics, which is a method for controlling neural activities by light. Since two cation channelrhodopsins were identified from the chlorophyte alga Chlamydomonas reinhardtii, recent advances in genomic research have revealed a wide variety of channelrhodopsins including anion channelrhodopsins (ACRs), describing their highly diversified molecular properties (e.g., spectral sensitivity, kinetics and ion selectivity). Here, we report two channelrhodopsin-like rhodopsins from the Colpodellida alga Vitrella brassicaformis, which are phylogenetically distinct from the known channelrhodopsins. Spectroscopic and electrophysiological analyses indicated that these rhodopsins are green- and blue-sensitive pigments (λmax = ~ 550 and ~ 440 nm) that exhibit light-dependent ion channeling activities. Detailed electrophysiological analysis revealed that one of them works as a monovalent anion (Cl-, Br- and NO3-) channel and we named it V. brassicaformis anion channelrhodopsin-2, VbACR2. Importantly, the absorption maximum of VbACR2 (~ 440 nm) is blue-shifted among the known ACRs. Thus, we identified the new blue-shifted ACR, which leads to the expansion of the molecular diversity of ACRs.

Aggregation-Induced Emission in Tetrathia[8]circulene Octaoxides via Restriction of the Dynamic Motion of their Negatively Curved π-Frameworks.

Curved polycyclic aromatic hydrocarbons exhibit intriguing properties, but their flexible and dynamic nature is often considered to be unfavorable for achieving excellent emission properties. In this study, we prepared tetrathia[8]circulene octaoxides that adopt a negatively curved conformation. We found that these molecules exhibit aggregation-induced emission (AIE) that originates from the restriction of the dynamic motion of their saddle-shaped π-frameworks in the solid and aggregated states.

Irreverent Nature of Dissymmetry Factor and Quantum Yield in Circularly Polarized Luminescence of Small Organic Molecules.

Recently, a rational modification of small organic molecules has attracted considerable attention for designing advanced materials with enhanced circularly polarized luminescence (CPL) activity. A particular emphasis has been placed on fully allowed π-π* transition of rigid aromatic systems, due to their relatively superior emission properties or quantum yields of luminescence (Φlum). However, their dissymmetry factors (g lum), differential left and right CPL intensities, are typically disappointingly low at least in one to two orders of magnitude. Truly useful organic CPL materials, rated by a circular polarization luminosity index (ΛCPL) per single molecule, possess both |g lum| and Φlum values high. However, how to improve these two factors simultaneously with a proper molecular design is an open question. Here, we addressed this issue by theoretical and statistical inspection on a possible relation of the g lum and Φlum values. According to the analysis, we propose simple, unpretentious, yet pertinent guidelines for designing superior organic CPL materials for the future with large ΛCPL values.

Synthesis of Tetraaza[8]circulenes from Tetrathia[8]circulenes through an SNAr-Based Process.

The synthesis of highly planar tetraaza[8]circulenes from tetrathia[8]circulenes through oxidation followed by a nucleophilic aromatic substitution reaction with arylamines is presented. Photophysical and electrochemical properties of tetraaza[8]circulenes were investigated and compared to those of tetrathia[8]circulenes. The tetraaza[8]circulene exhibited bright fluorescence both in solution and solid states.