Disentangling Excimer Emission from Chiral Induction in Nanoscale Helical Silica Scaffolds Bearing Achiral Chromophores

The synthesis and characterization of diketopyrrolopyrroles and perylenemonoimidodiesters linked to a substituted benzoic acid in the ortho, meta, and para positions, are reported. Grafting of these dyes on the surface of chiral silica nanohelices is used to probe how the morphology of the platform at the mesoscopic level affects the induction of chiroptical properties onto achiral molecular chromophores. The grafted structures are weakly (diketopyrrolopyrroles) or strongly (perylenemonoimidodiesters) emissive, exhibiting both locally-excited state emission and a broad, structureless emission assigned to excimers. The dissymmetry factors obtained using circular dichroism highlight optimized supramolecular organization between the chromophores for enhancing the chiroptical properties of the system. In the ortho- derivatives, poor organization due to steric hindrance is reflected in a low density of chromophores on walls of the silica-nanostructures (<0.1 vs. >0.3 and up to 0.6 molecules/nm² for the ortho and meta or para derivatives, respectively) and lower g_abs values than in the other derivatives (g_abs<2×10⁻⁵ vs 6×10⁻⁵ for the ortho and para derivatives, respectively). The para derivatives presented a better organization and increased values of g_abs. All grafted chromophores evidence varying degrees of excimer emission which was not found to directly correlate to their grafting density.     

Genetic and expression analysis of SNPs in the human deoxyribonuclease II: SNPs in the promoter region reduce its in vivo activity through decreased promoter activity

Five SNPs in the human DNase II gene have been reported to be associated with rheumatoid arthritis (RA). Genotype and haplotype analysis of 14 SNPs, nine SNPs of which reported in the NCBI dbSNP database in addition to these five SNPs, was performed in healthy subjects. The enzymatic activities of the amino acid substituted DNase II corresponding to each SNP and serum DNase II in healthy Japanese, and promoter activities derived from each haplotype of the RA‐related SNPs were measured. Significant correlations between genotype in each RA‐related SNP and enzymatic activity levels were found; alleles associated with RA exhibited a reduction in serum DNase II activity. Furthermore, the promoter activities of each reporter construct corresponding to predominant haplotypes in three SNPs in the promoter region of the gene exhibited significant correlation with levels of serum DNase II activity. These findings indicate these three SNPs could alter the promoter activity of DNASE2, leading to a decline in DNase II activity in the serum through gene expression. Since the three SNPs in the promoter region of the DNase II gene could affect in vivo DNase II activity through reduction of the promoter activity, it is feasible to identify these SNPs susceptible to RA.     

Halichoblelides B and C,potent cytotoxic macrolides from a Streptomyces species separated from a marine fish

Halichoblelide B (1) and C (2), novel macrolides with potent cytotoxicity against tumor cells in culture, have been isolated from a strain of Streptomyces hygroscopicus originally derived from the marine fish Halichoeres bleekeri, and their absolute stereostructures have been elucidated on the basis of spectroscopic analyses using 1D and 2D NMR techniques and chemical transformations. These compounds exhibited significant cytotoxicity against human cancer cell lines.     

Complexation behaviour of a CT complex composed of 9,10-bis(3,5-dihydroxyphenyl)anthracene and viologen derivatives

A chiral charge-transfer (CT) complex was formed using achiral 9,10-bis(3,5-dihydroxyphenyl)anthracene (BDHA) as an electron donor and achiral 1,1′-dimethyl-4,4′-bipyridinium dichloride (MVCl₂) as an electron acceptor. This chiral CT complex can include n-alkyl alcohol molecules as guests. On the other hand, when 1,1′-diphenyl-4,4′-bipyridinium dichloride and 1,1′-dibenzyl-4,4′-bipyridinium dichloride were used as electron acceptors, achiral CT complexes without guests were formed. It was found that the chiral crystallisation of the BDHA/MVCl₂–CT host system was caused by steric and electric intermolecular interactions between host component molecules BDHA and MVCl₂ during crystallisation.     

Stereoselective synthesis of 3-alkylideneoxindoles via palladium-catalyzed domino reactions

We have developed efficient catalytic methods for the stereoselective and diversity synthesis of various (E)-, (Z)-, and disubstituted 3-alkylideneoxindoles and 3-alkylidenebenzofuran-2-ones via palladium-catalyzed Heck/Suzuki-Miyaura, Heck/Heck, and Heck/carbonylation/Suzuki-Miyaura domino reactions.     

Colored supramolecular charge-transfer host system using 10,10′-dihydroxy-9,9′-biphenanthryl and 2,5-disubstituted-1,4-benzoquinone

A colored charge-transfer (CT) host complex is formed using racemic (rac)-10,10′-dihydroxy-9,9′-biphenanthryl, which has a large and widely π-conjugated phenanthrene ring, as the electron donor and 2,5-disubstituted-1,4-benzoquinone as the electron acceptor. This CT host complex can include aromatic molecules as guests and its color and diffuse reflectance spectra (DRS) change according to the type of guest molecules included. Characteristically, it is possible to tune the color and DRS of the inclusion CT complex by changing the type of the component 2,5-disubstituted-1,4-benzoquinone.     

Effect of molecular weight on the morphology of polystyrene/poly(methyl methacrylate) composite particles prepared by the solvent evaporation method

The effect of molecular weight on the morphology of polystyrene (PS)/poly(methyl methacrylate) (PMMA) composite particles was investigated. PS/PMMA composite particles with different molecular weights (M*=MwPS+MwPMMA)/2 approximately 2x10(4)-1x10(6) g.mol(-1)) were prepared by the release of toluene (T) from PS/PMMA/T (1/1/24, w/w/w) droplets dispersed in an aqueous solution of polyoxyethylene nonylphenyl ether nonionic surfactant (Emulgen 911). As T evaporated, the spherical droplets phase separated, resulting in snowmanlike composite particles with Janus morphology. The nonspherical shape was closely related to the morphology, which depended on M*. The interfacial tension between the phase-separated PS and PMMA phases increased with an increase in M*, and this would allow the formation of the snowmanlike shape to decrease the interfacial area between the PS and the PMMA phases.