Ion valence-gated photochromism of an aza-crowned diarylethene.

A non-photochromic diarylethene 2o with an N-phenylaza-15-crown-5 was synthesized. When the nitrogen atom in the aza-crown ring was protonated, it became photochromic due to the prevention of a twisted intramolecular charge transfer (TICT). Although addition of a monovalent metal cation (Li+, Na+, K+, Rb+, Cs+, Cu+, Ag+) in acetonitrile could not stop the TICT so that it was not photochromic, the addition of a multivalent metal cation (Mg2+, Ca2+, Sr2+, Ba2+, Fe2+, Ni2+, Al3+, Sb5+) changed 2o to be photochromic due to the strong attraction of the lone pair on the nitrogen atom. In the presence of excess Cu2+, 2o was oxidized to be EPR-detectable 2o·+, which was thermally unstable as well as inert towards visible-light irradiation. However, 2o·+ was further oxidized to be fairly stable 2o2+ by the irradiation of 365-nm light in the presence of Cu2+. ESI-MS measurements strongly suggested the generation of 2o·+ by mixing 2o with Cu(ClO4)2 in acetonitrile, and the transformation of 2o·+ to 2o2+ by successive 365-nm light irradiation. Fe3+ similarly worked as the oxidant, but the two-step oxidation of 2o to 2o2+ occurred more easily.

Ambient pH signaling regulates expression of the serine protease gene (spr1) in pine wilt nematode-trapping fungus, Monacrosporium megalosporum.

We have cloned and characterized spr1, a putative serine protease gene, from a nematode-trapping fungus, Monacrosporium megalosporum. The gene was present as a single copy in the genome. The predicted protein sequence of spr1 is homologous to the putative cuticle-degrading serine proteases PII and Azo1 from the nematode-trapping fungus, Arthrobotrys oligospora. In the 5' untranslated region near the initiation codon, consensus sequences to an AreA binding site, a well-known mediator of nitrogen metabolite repression in the fungus Aspergillus nidulans, a CreA binding site, a carbon response regulator in A. nidulans, and a PacC binding site, a transcription factor that responds to ambient pH signals in A. nidulans were found. However, spr1 was not regulated by carbon or nitrogen source, and exogenous protein did not induce expression of spr1. The transcription of the spr1 gene of this fungus was significantly affected by ambient pH. Based on RT-PCR, the product of the spr1 gene was not transcribed at pH 4, whereas under alkaline conditions such as pH 8 and 9, the spr1 gene was transcribed well. These results indicate that the spr1 gene is controlled only by a PacC homologue. Moreover, the expression profile of the spr1 gene corresponded with the pH-dependent physiology of this fungus.

Acetylacetonato-based pincer-type nickel(ii) complexes: synthesis and catalysis in cross-couplings of aryl chlorides with aryl Grignard reagents.

In this work, three different types of acetylacetonato-based pincer-type nickel(ii) complexes (2) were prepared. Complex 2a possessed the tridentate ONN ligand, which was constructed by the condensation reaction of acetylacetone with N,N-diethylethylenediamine. Complex 2b contained the PPh2 donor group in contrast to the NEt2 group in 2a, i.e., an ONP ligand framework. Complex 2c was composed of the NNN ligand, which was prepared by the reaction of 4-((2,4,6-trimethylphenyl)amino)pent-3-en-2-one with N,N-diethylethylenediamine. In addition to X-ray diffraction analysis, these complexes were characterized spectroscopically. Their catalytic activity for a cross-coupling reaction of aryl halides with aryl Grignard reagents was also evaluated. Among these complexes, 2b acted as an effective catalyst for the cross-coupling reaction using aryl chlorides as electrophiles. The electronic properties of these Ni(ii) complexes were investigated by cyclic voltammetry and density functional theory calculations.

Synthesis and hybridization properties of oligonucleotides containing (2S,3R)-9-(2,3,4-trihydroxybutyl)adenine.

The synthesis and properties of oligonucleotides (ONs) containing 9-(2,3,4-trihydroxybutyl)adenine, A(C2) and A(C3), are described. The ON containing A(C2) involves the 3'-->4' and 3-->5' phosphodiester linkages in the strand, whereas that containing A(C3) possesses the 3'-->4' and 2'-->5' phosphodiester linkages. It was found that incorporation of the analogs, A(C2) or A(C3), into ONs significantly reduces the thermal and thermodynamic stabilities of the ON/DNA duplexes, but does not largely decrease the thermal and thermodynamic stabilities of the ON/RNA duplexes as compared with the case of the ON/DNA duplexes. It was revealed that the base recognition ability of A(C2) is greater than that of A(C3) in the ON/RNA duplexes.

Practical remediation of the PCB-contaminated soils.

A practical method for the elimination of PCBs from PCB-contaminated soil has been developed by the combination of Soxhlet extraction using a newly-developed modified Soxhlet extractor possessing an outlet valve on the extraction chamber with the chemical degradation. Various types of PCBs contaminated in soils could be completely extracted in refluxing hexane, and the subsequent hydrodechlorination could also be completed within 1 h in a hexane-MeOH (1 : 5) solution in the presence of Pd/C and Et3N under ordinary hydrogen pressure and temperature without the transfer of the extracted PCBs to other reaction container (a complete one-pot procedure). The present system is quite useful as a simple, safe, mild and reliable remediation method of PCB-contaminated soil.

Circadian rhythm of atrioventricular conduction predicts long-term survival in patients with chronic atrial fibrillation.

The R-R interval of the electrocardiogram during atrial fibrillation (AF) appears absolutely irregular. However, the Poincaré plot of the R-R interval reveals a sector shape of distribution that is unique to AF. Furthermore, the height of lower envelope (LE1.0) of the distribution and the degree of scatter above the envelope (scattering index) may reflect the refractoriness and concealment of atrioventricular (AV) conduction, respectively. We previously observed that both the LE1.0 and scattering index show clear circadian rhythms in patients with chronic AF and that the rhythms are blunted in those with congestive heart failure and chronic AF. In the present study, we examined if the blunted circadian rhythm of the AV conduction has prognostic value in patients with chronic AF. We studied a retrospective cohort of 120 patients who underwent 24h Holter monitoring at baseline. During an observation period of 33 +/- 16 mon, there were 25 deaths (21%) including 13 cardiac and 8 stroke deaths. All patients showed significant circadian rhythms in both LE1.0 and scattering index with acrophases occurring at night; however, patients dying subsequently from cardiac causes, but not those from fatal stroke were blunted in the circadian rhythms (the amplitudes were < 55% of those in surviving patients). Furthermore, the reduced circadian amplitude of scattering index was an increased risk for cardiac death even after adjustment of coexisting cardiovascular risks [adjusted relative risk (95% confidence interval) per 1-SD decrement, 4.24 (1.54-11.6)]. When patients were divided by the circadian amplitude of the scattering index of 36.5 msec (mean minus 1-SD), the 5yr cardiac mortality below and above the cutoff was 57 and 6%, respectively (log-rank test, p < 0.001). We conclude that the blunted circadian rhythm of AV conduction is an independent risk for cardiac death in patients with chronic AF.

Practical method for PCB degradation using Pd/C-H2-Mg system.

Polychlorinated biphenyls (PCBs) were mainly used as lubricants and coolants in electrical equipment. However, their chemical stabilities as well as hydrophobic properties caused persistent environmental pollution and damage to human health based on their bioaccumulative property. PCBs are currently targeted for worldwide elimination and should be disposed by 2028 based on the Stockholm Convention on Persistent Organic Pollutants. The conventional PCB degradation methods require high-heat, high-pressure or/and strongly basic conditions. The development of a safer and more practical method, therefore, is desired. We have reported a catalytic degradation method of PCBs based on a palladium on carbon (Pd/C)-catalyzed dechlorination in the presence of Et(3)N under ambient hydrogen pressure and temperature. In this study, we demonstrate a more practical system using magnesium metal instead of Et(3)N for the dechlorination of a variety of aromatic chlorides. The method was applicable for the complete degradation of a variety of PCB mixtures, such as Aroclor 1242, 1248, 1254 and PCBs removed from a capacitor to produce only biphenyl and magnesium chloride as the maritime component, both of which are less toxic and easily separable. Moreover, the Pd/C could be recovered and reused at least five times without any loss of catalytic activity. The present Pd/C-Mg-H(2) system is a simple, safe, inexpensive, and environmentally-benign degradation method of PCBs.

Pd/C-catalyzed dechlorination of polychlorinated biphenyls under hydrogen gas-free conditions.

The simultaneous use of catalytic amount of palladium on carbon (Pd/C) and Mg metal (1.5-2.0 equiv vs. Cl numbers of the substrates) in MeOH achieved the complete dechlorination of a variety of aryl chlorides at room temperature under a nitrogen atmosphere in the absence of hydrogen gas. The present method could be successfully used for the detoxification of PCBs based on the dechlorination reaction. Both virgin PCBs, such as Aroclors 1242, 1248 and 1254, and used PCBs as a high-tension capacitor oil, were smoothly dechlorinated into harmless biphenyl without any byproducts within 2h at rt. The distinctive features of this method are convenience and safety due to no needs for the pretreatment of catalyst and Mg and complete degradation of PCBs under mild conditions without hydrogen gas.

NMR study for self-aggregation of 1-butyl-3-methylimidazolium bromide in aqueous solution.

Self-aggregation of 1-butyl-3-methylimidazolium bromide ([bmim]Br) in D(2)O has been investigated using NMR spectroscopy. The (1)H spin-lattice relaxation times (T(1)) of the [bmim](+) increased with the decrease of concentration in the range of 0.1-3.0 mol dm(-3) as expected, however, in contrast, the (1)H-T(1) decreased below 0.1 mol dm(-3). The estimated (13)C-activation energies indicated that the rotational mobility of the butyl-chain was more restricted than that of the imidazole ring at 0.1 mol dm(-3), whereas such a significant difference was not observed at 3.0 mol dm(-3). These results suggest that [bmim](+) forms micelle-like aggregations below 0.1 mol dm(-3) in D(2)O.

Polyketide synthase gene responsible for citrinin biosynthesis in Monascus purpureus.

Citrinin produced by Aspergillus, Penicillium, and Monascus species is a polyketide compound that has nephrotoxic activity in mammals and is bactericidal toward gram-positive bacteria. To avoid the risk of citrinin contamination in other fermentation products produced by Monascus purpureus, knowledge of the citrinin biosynthetic genes is needed so that citrinin-nonproducing strains can be generated. We cloned a polyketide synthase (PKS) gene from M. purpureus with degenerate primers designed to amplify the conserved region of a ketosynthase domain of a fungal PKS. A 13-kb genomic DNA fragment was identified that contained a full-length PKS gene (pksCT) of 7,838 bp with a single 56-bp intron. pksCT encodes a 2,593-amino-acid protein that contains putative domains for ketosynthase, acyltransferase, acyl carrier protein (ACP), and a rare methyltransferase. There was no obvious thioesterase domain, which usually is downstream of the ACP domain in multi-aromatic-ring PKSs. pksCT transcription was correlated with citrinin production, suggesting that the pksCT gene product was involved in citrinin biosynthesis. Homologous recombination between the wild-type allele and a truncated disruption construct resulted in a pksCT-disrupted strain of M. purpureus. The disruptant did not produce citrinin, but a pksCT revertant generated by successive endogenous recombination events in the pksCT disruptant restored citrinin production, indicating that pksCT encoded the PKS responsible for citrinin biosynthesis in M. purpureus.