Control of Chromophore Symmetry by Positional Isomerism of Peripheral Substituents

The first example of the control of porphyrinoid chromophore symmetry based on the positional isomerism of peripheral substituents has been achieved by preparing tetraazaporphyrins (TAPs) with C_4h, D_2h, C_2v, and C_s symmetry due to the relative arrangement of peripheral tert‐butylamino and cyano groups as push and pull substituents, respectively. The four structural isomers were successfully isolated and characterized by ¹H NMR spectroscopy and X‐ray crystallography. The band morphology in the Q‐band region varies depending on the molecular symmetry due to the significant perturbation introduced into the chromophore by the push and pull substituents. The C_4h and C_2v isomers exhibit a single Q band, whereas the Q bands of the D_2h and C_s isomers show a marked splitting. The magnetic circular dichroism spectra indicate that the push–pull TAPs retain the properties of the 16‐membered 18π‐electron perimeter generally observed for porphyrinoids. Theoretical calculations have demonstrated that the perturbation introduced by the substituents lowers the D_4h symmetry of the parent TAP π‐conjugated system, and this results in significant spectral changes. A novel approach to the fine‐tuning of the spectral properties of porphyrinoids based on changes in the chromophore symmetry is described.     

Thermal or Mechanical Stimuli‐Induced Photoluminescence Color Change of a Molecular Assembly Composed of an Amphiphilic Anthracene Derivative in Water

Molecular assemblies that change photoluminescence color in response to thermal or mechanical stimulation without dissociation into the monomeric states in water are described herein. A dumbbell‐shaped amphiphilic compound forms micellar molecular assemblies in water and exhibits yellow photoluminescence derived from excimer formation of the luminescent core, which contains a 2,6‐diethynylanthracene moiety. Annealing of the aqueous solution induces a photoluminescence color change from yellow to green (λ_{em, max}=558→525 nm). The same photoluminescence color change is also achieved by rubbing the yellow‐photoluminescence‐emitting molecular assemblies adsorbed on glass substrates with cotton wool in water. The observed green photoluminescence is ascribed to micelles that are distinct from the yellow‐photoluminescence‐emitting micelles, on the basis of transmission electron microscopy observations, atomic force microscopy observations, and dynamic light scattering measurements. We examined the relationship between the structure of the molecular assemblies and the photophysical properties of the anthracene derivative in water before and after thermal or mechanical stimulation and concluded that thermal or mechanical stimuli‐induced slight changes of the molecular‐assembled structures in the micelles result in the change in the photoluminescence color from yellow to green in water.     

Development of a certified reference material for the determination of perfluorooctanoic acid

A certified reference material (CRM) for the determination of perfluorooctanoic acid (PFOA) has been issued as NMIJ CRM 4056-a by the National Metrology Institute of Japan, National Institute of Advanced Industrial Science and Technology (NMIJ/AIST). Purity (kg kg^?1) based on a titration method was determined by subtracting the mass fractions of impurities measured using liquid chromatography/mass spectrometry (LC/MS) from those of acids expressed as PFOA measured by a neutralization potentiometric titration. To validate an obtained result, purity based on a mass balance method was determined by subtracting the mass fractions of impurities, measured using LC/MS, Karl-Fischer titration (KFT), and vacuum evaporation, from 1 kg kg^?1. Results from both titration and mass balance methods were in agreement within the accepted limits of uncertainty. The certified purity of NMIJ CRM 4056-a was determined to be 0.959 kg kg^?1, calculated as the mean of the results obtained with the two methods. The standard uncertainty of the certified purity was evaluated from purity evaluations as well as from sample homogeneity and stability obtained from LC/MS and KFT analyses. Consequently, the expanded uncertainty was estimated to be 0.005 kg kg^?1 with a coverage factor of k = 2.     

Acidic‐pH‐Activatable Fluorescence Probes for Visualizing Exocytosis Dynamics

Live imaging of exocytosis dynamics is crucial for a precise spatiotemporal understanding of secretion phenomena, but current approaches have serious limitations. We designed and synthesized small‐molecular fluorescent probes that were chemically optimized for sensing acidic intravesicular pH values, and established that they can be used to sensitively and reliably visualize vesicular dynamics following stimulation. This straightforward technique for the visualization of exocytosis as well as endocytosis/reacidification processes with high spatiotemporal precision is expected to be a powerful tool for investigating dynamic cellular phenomena involving changes in the pH value.     

Study of the thermal degradability of poly(α-methylstyrene) with modified end groups

To induce degradabilities in polymers in response to environmental conditions, endm odification reactions of poly(α-methylstyrene) (PMS) derivatives were carried out. 2-Phenylallyl halide derivatives such as 2-phenylallyl bromide, 2-(p-tolyl)allyl bromide, and α-trifluoromethylstyrene were found to be suitable end-modification agents. For example, the ω-2-phenylallyl-PMS derivative was prepared with almost quantitative functionality by the reaction of the living PMS derivative with 2-phenylallyl bromide. In a similar way, ω-3,3-difluoro-2-phenylallyl- and ω-2-(4-toly)allyl-PMS derivatives were synthesized. Based on thermogravimetric analysis, the onset of the degradation temperature of the endmodified PMS derivatives decreased in the following order: ω-hydrogen- > ω-3,3-difluoro-2-phenylallyl- > ω-2-phenylallyl- > ω-2-(p-tolyl)allyl-PMS. Actually, the onset temperature of ω-2-(p-tolyl)allyl-PMS derivatives was 50°C lower than that of ω-H-PMS derivatives. These results indicate that the active species is produced effectively at the endunsaturated bond, which initiates depolymerization of the polymer at rather low temperatures. Therefore, it is concluded that a 2-phenylallyl substituent at the end of the PMS chain induces effective degradation through a radical mechanism.     

Organic electroluminescent and nonlinear optical materials

The multilayer electroluminescent(EL) devices composed of vacuum-sublimed organic films are discussed with the aims of achieving high luminance and proposing an optical micro-cavity. For the former purpose, requirements for confinements of carriers and excitons within the thin emissive layer are shown by taking accounts of ionization potentials, electron affinities and excitation energies in organic thin films. Concerning the interference effect of emitted light, we show the variation in the intensity of emission and a strongly directional light from the micro-cavity. Second-order nonlinear optical(NLO) films are designed by preparing noncentrosymmetric LB multilayers composed of an pyrazine derivative with large hyperpolarizability and arachidic acid. Third-order nonlinear optical(NLO) films are proposed by using polyarylenevinylene films. In order to fabricate excellent third-order nonlinear optical(NLO) films, highly oriented polyarylenevinylene films are prepared by using a LB technique.     

Syntheses of β-amidovinyltellurides and oxazoles by addition reactions of alkynes with benzenetellurinyl trifluoromethanesulfonate in acetonitrile

Benzenetellurinyl trifluoromethanesulfonate in conjunction with acetonitrile readily effected amidotellurinylation reactions with alkynes. Most of the addition reactions proceeded in a trans fashion to form the (E)-β-acetamidovinyl phenyl telluroxides. Subsequently, it was found that the prevailing Markovnikov adducts from terminal alkynes immediately isomerized to (Z)-isomers which were isolated as the corresponding vinyltellurides. On the other hand, the adducts derived from internal alkynes thermally underwent a spontaneous intramolecular cyclization to be transformed eventually into oxazoles.     

Effects of Roxadustat on Erythropoietin Production in the Rat Body

Anemia is a major complication of chronic renal failure. To treat this anemia, prolylhydroxylase domain enzyme (PHD) inhibitors as well as erythropoiesis-stimulating agents (ESAs) have been used. Although PHD inhibitors rapidly stimulate erythropoietin (Epo) production, the precise sites of Epo production following the administration of these drugs have not been identified. We developed a novel method for the detection of the Epo protein that employs deglycosylation-coupled Western blotting. With protein deglycosylation, tissue Epo contents can be quantified over an extremely wide range. Using this method, we examined the effects of the PHD inhibitor, Roxadustat (ROX), and severe hypoxia on Epo production in various tissues in rats. We observed that ROX increased Epo mRNA expression in both the kidneys and liver. However, Epo protein was detected in the kidneys but not in the liver. Epo protein was also detected in the salivary glands, spleen, epididymis and ovaries. However, both PHD inhibitors (ROX) and severe hypoxia increased the Epo protein abundance only in the kidneys. These data show that, while Epo is produced in many tissues, PHD inhibitors as well as severe hypoxia regulate Epo production only in the kidneys.     

Presence of β-Turn Structure in Recombinant Spider Silk Dissolved in Formic Acid Revealed with NMR

Spider dragline silk is a biopolymer with excellent mechanical properties. The development of recombinant spider silk protein (RSP)-based materials with these properties is desirable. Formic acid (FA) is a spinning solvent for regenerated Bombyx mori silk fiber with excellent mechanical properties. To use FA as a spinning solvent for RSP with the sequence of major ampullate spider silk protein from Araneus diadematus, we determined the conformation of RSP in FA using solution NMR to determine the role of FA as a spinning solvent. We assigned ¹H, ¹³C, and ¹⁵N chemical shifts to 32-residue repetitive sequences, including polyAla and Gly-rich regions of RSP. Chemical shift evaluation revealed that RSP is in mainly random coil conformation with partially type II β-turn structure in the Gly-Pro-Gly-X motifs of the Gly-rich region in FA, which was confirmed by the ¹⁵N NOE data. In addition, formylation at the Ser OH groups occurred in FA. Furthermore, we evaluated the conformation of the as-cast film of RSP dissolved in FA using solid-state NMR and found that β-sheet structure was predominantly formed.