Palladium-catalyzed selenoacylation of allenes leading to the regioselective formation of functionalized allyl selenides

Palladium-catalyzed regio- and stereoselective selenoacylation of allenes with selenol esters proceeded to produce functionalized allyl selenides with the acyl moiety at the inner carbon and the SePh group at the terminal carbon in high yields. A mechanism accounting for the observed regio- and stereoselectivities is proposed based on the results of DFT calculations.     

Nucleic Acid-to-Small Molecule Converter through Amplified Hairpin DNA Circuits

Many microRNAs (miRNAs) are characteristically found in cancer cells, making miRNAs promising marker biomolecules for cancer diagnosis and therapeutics. However, it is challenging to use miRNA as a cancer signature because it is difficult to convert the nucleic acid sequence information into molecular functionality. To address this challenge, we realize nucleic acid-to-small molecule converters using hairpin DNA circuits. Harnessing a Staudinger reduction as a trigger for the conversion, we constructed hybridization chain reaction (HCR) and catalytic hairpin assembly (CHA) circuits that respond to oncogenic miR-21. Fluorophore and dye molecules were released in response to miR-21 through the HCR, providing fluorogenic and chromogenic readouts. Selective cytotoxicity in miR-21-abundant cells was realized by the CHA to release the anticancer drug SN-38. This would be the first example of selective activation of a small-molecule prodrug triggered by oncogenic miRNA in human living cells.     

Reductive amination of furfural toward furfurylamine with aqueous ammonia under hydrogen over Ru-supported catalyst

Poly(N-vinyl-2-pyrrolidone)-capped ruthenium-supported hydroxyapatite (Ru-PVP/HAP) shows significant activity for the synthesis of furfurylamine (FAM) via the reductive amination of furfural. As-prepared 5 wt% Ru-PVP/HAP affords 50 % yield of FAM in 25 % NH₃ aqueous solution under pressurized H₂ gas (2.5 atm), and the highest yield approaches 60 % at 4.0 H₂ atm. Comparison between the activities over four Ru-supported HAP catalysts prepared with different methods and the results of X-ray absorption spectroscopy suggested that the metallic Ru cluster is the active center for the reductive amination of furfural. Transmission electron microscope and inductively-coupled plasma analysis indicated that the as-prepared 5 wt% Ru-PVP/HAP catalyst possessed 4.0 wt% PVP-capped Ru clusters with average diameter of 1.7 ± 0.3 nm on HAP support. It was also demonstrated that the reductive amination approach with Ru-PVP/HAP catalyst, NH₃ aq. and pressurized H₂ gas has capability for transformation of aromatic aldehydes to the corresponding aromatic amines. According to these results, it is concluded that Ru(0) cluster supported on HAP will represent a suitable catalyst for widely-usable reductive amination to convert an aldehyde functionality towards an amine.     

Degradation of bisphenol A by <Emphasis Type="Italic">Bacillus pumilus</Emphasis> isolated from kimchi,a traditionally fermented food

Novel bisphenol A (BPA)-degrading bacterial strains, designated as BP-2CK, BP-21DK, and BP-22DK, were isolated from kimchi, a traditionally fermented food. These isolates were identified as Bacillus pumilus and efficiently degraded BPA in a medium supplemented with nutrients such as peptone, beef extract, and yeast extract. Strains BP-2CK, BP-21DK, and BP-22DK successfully degraded 25, 25, and 50 ppm of BPA, respectively, and all strains exhibited BPA-degrading activity in the presence of 10% NaCl. Accumulation of the metabolites including 4-hydroxyacetophenone, one of the intermediates produced by the other BPA-degrading bacteria, was not observed in BPA degradation by the isolated strains. These results indicate that the isolated food-derived bacteria are applicable for the construction of efficient and safer systems for the removal of BPA.     

Succinct data structures for flexible text retrieval systems

We propose succinct data structures for text retrieval systems supporting document listing queries and ranking queries based on the tf*idf (term frequency times inverse document frequency) scores of documents. Traditional data structures for these problems support queries only for some predetermined keywords. Recently Muthukrishnan proposed a data structure for document listing queries for arbitrary patterns at the cost of data structure size. For computing the tf*idf scores there has been no efficient data structures for arbitrary patterns.Our new data structures support these queries using small space. The space is only 2/ times the size of compressed documents plus 10n bits for a document collection of length n, for any 0<1. This is much smaller than the previous O(nlogn) bit data structures. Query time is O(m+qlogn) for listing and computing tf*idf scores for all q documents containing a given pattern of length m. Our data structures are flexible in a sense that they support queries for arbitrary patterns.     

Circularly polarized luminescence of rhodamine B in a supramolecular chiral medium formed by a vortex flow

Sucked into the vortex: Hydrogels with embedded Rhodamine?B dye showed stir-induced circularly polarized luminescence (CPL; see picture), the sense of which can be controlled by switching the stir direction from clockwise (CW) to counterclockwise (CCW) with slow cooling from the sol to gel states. The chiral alignment of the dye was erased by heating the sample above the gel-sol transition temperature.     

Mass migration on a polymer surface caused by photoinduced molecular rotation

We demonstrated the formation of a photoinduced surface relief grating using thin films comprising a photochromic molecular motor, 9-(2-phenyl-2,3-dihydro-cyclopenta[a]naphthalen-1-ylidene)-9H-fluorene. Results show that mass migration occurred by patterned light irradiation prepared from interfered laser beams and a photomask.     

A single-cell drug efflux assay in bacteria by using a directly accessible femtoliter droplet array

Active efflux of drugs, such as antibiotics, from a cell is one of the major mechanisms that cause multi-drug resistance in bacteria. Here we report a method to assess drug efflux activity in individual Escherichia coli cells enclosed and isolated in a directly accessible femtoliter droplet array with a fluorogenic compound. The inhibitory effect of a chemical compound on an exogenously expressed efflux pump system from pathogenic bacteria was easily detected at the single-cell level. We also present a proof-of-principle experiment to screen for the gene encoding a drug efflux pump by collecting individual droplets containing single cells in which the drug efflux activity was restored after introduction of the exogenous gene from pathogenic bacteria. Our approach will be a useful tool to screen novel pump inhibitors and efflux pump genes, and to overcome infectious diseases caused by multi-drug-resistant bacteria.     

Reverse enantioselectivity in the lipase-catalyzed desymmetrization of prochiral 2-carbamoylmethyl-1,3-propanediol derivatives

Enantioselective acetylation of 2-carbamoylmethyl-1,3-propanediol derivatives was catalyzed effectively by lipase PS to give monoacetates with high enantioselectivity: The enantioselectivity depended on the 2-carbamoylmethyl groups. The reaction of N-monoalkylcarbamoylmethyl-1,3-propanediol afforded the monoacetate with the (S)-configuration, whereas N,N-dialkylcarbamoylmethyl-1,3-propanediol gave the monoacetate with the (R)-configuration.