Double Heterohelicenes Composed of Benzo[b]- and Dibenzo[b,i]phenoxazine: A Comprehensive Comparison of Their Electronic and Chiroptical Properties.

Heterohelicenes are potential materials in molecular electronics and optics because of their inherent chirality and various electronic properties originating from the introduced heteroatoms. In this work, we comprehensively investigated two kinds of double NO-hetero[5]helicenes composed of 12H-benzo[b]phenoxazine (BPO) and 13H-dibenzo[b,i]phenoxazine (DBPO). These helicenes exhibit good electron-donor properties reflecting the electron-rich character of their monomers and were demonstrated to work as p-type semiconductors. The enantiomers of these helicenes show the largest class of dissymmetry factors for circularly polarized luminescence (CPL) (|gCPL| > 10-2) among helicenes reported to date. Interestingly, the signs of CPL are opposite for BPO and DBPO double helicenes of the same helicity. The origin of the large gCPL values and the inversion of the CPL sign was addressed by analysis of the transition electronic dipole moments and transition magnetic dipole moments based on TD-DFT calculations.

Oxidative stress inducers potentiate 2,3,7,8-tetrachlorodibenzo-p-dioxin-mediated pre-cardiac edema in larval zebrafish.

We reported the involvement of oxidative stress and prostaglandins including thromboxane and prostacyclin in pre-cardiac edema (early edema) caused by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). While the involvement of oxidative stress in TCDD-induced toxicity has been frequently reported, the mechanism of its action is still unclear. In the present study, oxidative stress inducers including paraquat, hydrogen peroxide (H2O2) and rotenone augmented early edema (edema) induced by a low concentration of TCDD (0.1 ppb) at 55 hr post fertilization (hpf), while each of them alone did not cause edema. Edema caused by TCDD plus oxidative stress inducers was almost abolished by antioxidants, an antagonist for thromboxane receptor (ICI-192,605) and an agonist for prostacyclin receptor (beraprost), suggesting that the site of action of these inducers was in the regular signaling pathway after activation of aryl hydrocarbon receptor type 2 (AHR2) by TCDD. Oxidative stress inducers also enhanced edema caused by an agonist for the thromboxane receptor (U46619), and the enhancement was also inhibited by antioxidants. Sulforaphane and auranofin, activators of Nrf2 that is a master regulator of anti-oxidative response, did not affect U46619-evoked edema but almost abolished TCDD-induced edema and potentiation by paraquat in both TCDD- and U46619-induced edema. Taken together, the results suggest that oxidative stress augments pre-cardiac edema caused by TCDD via activation of thromboxane receptor-mediated signaling in developing zebrafish. As paraquat and other oxidative stress inducers used also are environmental pollutants, interaction between dioxin-like compounds and exogenous source of oxidative stress should also be considered.

Synthesis and Electronic Properties of Directly Linked Dihydrodiazatetracene Dimers.

5,12-Dihydro-5,12-diazatetracene (DHDAT) dimers with different substitution patterns are synthesized: a symmetric one with a C-C bond between the monomer units (1) and two asymmetric ones with a C-N bond between the monomer units (2 and 3). The DHDAT units are planar in the C-C linked dimer 1 but perpendicularly oriented in the C-N linked dimers 2 and 3 (from X-ray analysis). The electronic ground-state interaction between the two units is large in 1 and small in 2 and 3. The emission behavior of 3 is different from that of other dimers and its monomer; it displays positive solvatochromism, characteristic for electron donor-acceptor molecules, despite its donor-donor type structure. Compound 3 exhibits a unique multi-step thermochromic emission behavior. The emission behavior is attributed to the asymmetric distribution of the HOMO and LUMO of DHDAT.

Phylogenetic and antigenic analysis of bovine parainfluenza virus type 3 isolated in Japan between 2002 and 2019.

Bovine parainfluenza virus type 3 (BPIV3) is one of the most important viral respiratory pathogens of cattle. In addition to the classical BPIV3 genotype A (BPIV3a), new genetic groups, genotype B (BPIV3b) and C (BPIV3c), have been identified and isolated in certain parts of the world. The present study aimed to investigate the genetic and antigenic characteristics of BPIV3 circulating in Japan. Seventy-three BPIV3 field strains were isolated from nasal samples of cattle between 2002 and 2019. Phylogenetic analysis of the phosphoprotein and hemagglutinin-neuraminidase genes showed that the isolates clustered into two genotypes, BPIV3a (49 %) and BPIV3c (51 %). The BPIV3a strains had more wide genetic variation than the rest of the genotypes. Additionally, new variants were obtained and designated them tentatively as subgroup 4 of the BPIV3a. The first Japanese BPIV3c was isolated in 2012, but here the BPIV3c NM2 strain was isolated from a sample collected four years earlier than the previous report. The antigenicity of ten BPIV3 strains including all three genotypes was assessed with a viral cross-neutralization test. Anti-sera against BPIV3a and BPIV3b cross-reacted well with both homologous and heterologous viruses. On the other hand, anti-sera against BPIV3c had reduced cross-reactivity to the heterologous viruses. Overall, our findings showed that genetically and antigenically divergent BPIV3 is prevalent in cattle in Japan. These results could provide a reference for molecular epidemiological characterization of BPIV3 and vaccine development.

Doxifluridine-conjugated 2-5A analog shows strong RNase L activation ability and tumor suppressive effect.

RNase L is activated by 2',5'-oligoadenylates (2-5A) at subnanomolar levels to cleave single-stranded RNA. We previously reported the hypothesis that the introduction of an 8-methyladenosine residue at the 2'-terminus of the 2-5A tetramer shifts the 2-5A binding site of RNase L. In this study, we synthesized various 5'-modified 2-5A analogs with 8-methyladenosine at the 2'-terminus. The doxifluridine-conjugated 8-methyladenosine-substituted 2-5A analog was significantly more effective as an activator of RNase L than the parent 5'-monophophorylated 2-5A tetramer and showed a tumor suppressive effect against human cervical cancer cells.

Photoconversion of 6,13-α-diketopentacene in the crystalline phase.

The photoconversion of a crystalline-phase precursor, 6,13-dihydro-6,13-ethanopentacene-15,16-dione (PDK), into pentacene was examined. Upon irradiation with 470 nm light, the photoconversion proceeded even in the crystalline phase. Although the rate of the crystalline phase photoconversion was much slower than that in solution, quantitative photoconversion was achieved upon lengthy photoirradiation. The photoconversion of PDK was also confirmed at the single µm-sized crystal level by observing fluorescence images and spectra of the PDK crystal using confocal microscopy. Destruction of the crystal was observed when some of the PDK molecules in the crystal were photoconverted into pentacene. These results indicate that the crystalline-phase photoconversion of PDK proceeded through the destruction of the crystal. Quantitative photoconversion was achieved as a result.