Photochemical reaction of silyl-substituted 1,4-disila(dewar-benzene) with isocyanide and phenylacetylene

The irradiation of silyl-substituted 1,4-disila(Dewar-benzene) 1 with light of wavelength λ > 320 nm in the presence of 2,6-dimethylphenyl-isocyanide or phenylacetylene produced 1,4-bis(di-tert-butylmethylsilyl)-2,3,5,6-tetraethyl-7-(2,6-dime-thylphenylimino)-1,4-disilabicyclo[2.2.1]hepta-2,5-diene 5 or 1,4-bis(di-tert-butylmethylsilyl)-2,3,5,6-tetraethyl-1-(2-phenylethynyl)-1,4-disilacyclohexa-2,5-diene 6 , respectively. The molecular structures of 5 and 6 were determined by spectroscopic data and X-ray crystallography. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:87–92, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20411     

Topologically-Interlocked Minicircles as Probes of DNA Topology and DNA-Protein Interactions

DNA minicircles exist in biological contexts, such as kinetoplast DNA, and are promising components for creating functional nanodevices. They have been used to mimic the topological features of nucleosomal DNA and to probe DNA-protein interactions such as HIV-1 and PFV integrases, and DNA gyrase. Here, we synthesized the topologically-interlocked minicircle rotaxane and catenane inside a frame-shaped DNA origami. These minicircles are 183 bp in length, constitute six individual single-stranded DNAs that are ligated to realize duplex interlocking, and adopt temporary base pairing of single strands for interlocking. To probe the DNA-protein interactions, restriction reactions were carried out on DNAs with different topologies such as free linear duplex or duplex constrained inside origami and free or topologically-interlocked minicircles. Except the free linear duplex, all tested structures were resistant to restriction digestion, indicating that the topological features of DNA, such as flexibility, curvature, and groove orientation, play a major role in DNA-protein interactions.     

DNA Origami Scaffolds as Templates for Functional Tetrameric Kir3 K+ Channels

In native systems, scaffolding proteins play important roles in assembling proteins into complexes to transduce signals. This concept is yet to be applied to the assembly of functional transmembrane protein complexes in artificial systems. To address this issue, DNA origami has the potential to serve as scaffolds that arrange proteins at specific positions in complexes. Herein, we report that Kir3 K⁺ channel proteins are assembled through zinc‐finger protein (ZFP)‐adaptors at specific locations on DNA origami scaffolds. Specific binding of the ZFP‐fused Kir3 channels and ZFP‐based adaptors on DNA origami were confirmed by atomic force microscopy and gel electrophoresis. Furthermore, the DNA origami with ZFP binding sites nearly tripled the K⁺ channel current activity elicited by heterotetrameric Kir3 channels in HEK293T cells. Thus, our method provides a useful template to control the oligomerization states of membrane protein complexes in vitro and in living cells.     

Stable and Highly Efficient Electrochemical Production of Formic Acid from Carbon Dioxide Using Diamond Electrodes

High faradaic efficiencies can be achieved in the production of formic acid (HCOOH) by metal electrodes, such as Sn or Pb, in the electrochemical reduction of carbon dioxide (CO₂). However, the stability and environmental load in using them are problematic. The electrochemical reduction of CO₂ to HCOOH was investigated in a flow cell using boron‐doped diamond (BDD) electrodes. BDD electrodes have superior electrochemical properties to metal electrodes, and, moreover, are highly durable. The faradaic efficiency for the production of HCOOH was as high as 94.7 %. Furthermore, the selectivity for the production of HCOOH was more than 99 %. The rate of the production was increased to 473 μmol m^?2 s^?1 at a current density of 15 mA cm^?2 with a faradaic efficiency of 61 %. The faradaic efficiency and the production rate are almost the same as or larger than those achieved using Sn and Pb electrodes. Furthermore, the stability of the BDD electrodes was confirmed by 24 h operation.     

A new secolactarane-type sesquiterpene from Strobilurus tephanocystis

A new sesquiterpenoid, strobiluric acid has isolated from the liquid culture extract of the fungus Strobilurus stephanocystis together with seven known sesquiterpenoids. Their structures were established based on spectroscopic data.     

Diastereoselective synthesis of useful building blocks by crotylation of beta-branched alpha-methylaldehydes with potassium crotyltrifluoroborates

The diastereoselective construction of stereotriads having consecutive methyl, hydroxy, and methyl substituents was realized by the substrate-controlled crotylation of beta-branched alpha-methylaldehydes with potassium crotyltrifluoroborates. Especially, crotylation of 2-(1,3-dithian-2-yl)propanal with potassium ( E)-crotyltrifluoroborate afforded, in good yield and with excellent diastereoselectivity, a useful building block that has different and potential functional groups on both ends.     

Preparation of apatite-type-silicate-supported precious metal catalysts for selective catalytic reduction of NOx

Apatite-type silicate supported precious metal catalysts were prepared and investigated for their catalytic activity in selective catalytic NO reduction. Single-phase La_9.33Si₆O₂₆ and La_8.33ASi₆O_25.5 (A=Ca, Sr, Ba) were obtained by a sol-gel method. Pd/La_9.33Si₆O₂₆ catalyst exhibited high activity for oxidation of C₃H₆, comparable to Pd/Al₂O₃ catalyst, although the specific surface area of La_9.33Si₆O₂₆ was lower than that of Al₂O₃. In addition, Pt/La_9.33Si₆O₂₆ catalyst exhibited higher activity for selective catalytic reduction of NO than Pt/Al₂O₃ catalyst. Substitution of Ba²⁺ for La³⁺ of La_9.33Si₆O₂₆ led to increased catalytic activity at low temperature.