A biochemical sniffer-chip for convenient analysis of gaseous formaldehyde from timber materials

A biochemical gas-sensor (sniffer-chip) with formaldehyde dehydrogenase (FALDH) was developed for convenient analysis of gaseous formaldehyde with high gas-selectivity. The sniffer-chip for formaldehyde in the gas phase was constructed by immobilizing FALDH to a Pt-electrode coated hydrophilic PTFE membrane. The oxidation current of NADH produced by the enzymatic reactions was measured by amperometric analysis. The calibration range of the sniffer-chip for formaldehyde in the gas phase was from 40 to 2000 ppb, which encountered the maximum permissible concentration of formaldehyde vapor in the residential house (80 ppb) and formaldehyde detection limit for the human sense of smell (410 ppb). As the resident-environmental application, the sniffer-chip was possible to measure the formaldehyde concentration from some timber materials (3 kinds of interior timber and 2 kinds of exterior formwork timber) within 3 min. The calculated concentration value by a regression analysis was consistent with those of a commercially available gas sensor and a gas detector tube for formaldehyde. The FALDH sniffer-tip would be effective and convenient approach to detect and measure gaseous formaldehyde with high gas-selectivity at the residential atmosphere. Correspondence: Kohji Mitsubayashi, Department of Biomedical Devices and Instrumentation, Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, 2-3-10 Kanda-Surugadai, Chiyoda-ku, Tokyo 101-0062, Japan     

Superperiodic assembly of 2,6-diethynylpyridine through weak hydrogen bonds at the 1-phenyloctane/HOPG interface

Regardless of the absence of alkyl chains and conventional hydrogen bonding sites as well as its small size, 2,6-diethynylpyridine forms an ordered array at the interface between 1-phenyloctane and highly oriented pyrolytic graphite (HOPG) under room temperature conditions, as revealed by scanning tunneling microscopy. We propose a model for the superperiodic molecular arrangement with reference to the bulk crystal structure, in which the surface pattern is governed by weak C-H...N and C-H...pi hydrogen bonds as well as the periodic potential of the underlying graphite surface.     

Stimuli induced structural changes of gold nanoparticle assemblies having sequential alternating amphiphilic peptides at the surface

Gold nanoparticles having sequential alternating amphiphilic peptide chains, Phe-(Leu-Glu)8, on the surface have been prepared. We describe structural control of the amphiphilic peptide coated gold nanoparticle assembly by a conformational transition of the surface peptides. Under the acidic condition, the conformation of the surface amphiphilic peptide was converted to a beta-sheet structure from an aggregated alpha-helix by incubation. Under this condition, the amphiphilic peptide coated gold nanoparticles formed a nanosheet assembly. The plasmon absorption maximum of the gold nanoparticles shifted to a shorter wavelength with the formation of the beta-sheet assembly of the surface peptide. This suggests that the structure of the peptide coated gold nanoparticle assembly could be controlled by the conformational transition of the surface peptide. Furthermore, the core gold nanoparticle could be fixed in the beta-sheet assembly in the state that stood alone. This system may be useful for novel molecular devices that exhibit quantized properties.     

Ion chemistry of 1H-1,2,3-triazole. 2. Photoelectron spectrum of the iminodiazomethyl anion and collision induced dissociation of the 1,2,3-triazolide ion

The 363.8 nm photoelectron spectrum of the iminodiazomethyl anion has been measured. The anion is synthesized through the reaction of the hydroxide ion (HO-) with 1 H-1,2,3-triazole in helium buffer gas in a flowing afterglow ion source. The observed spectrum exhibits well-resolved vibronic structure of the iminodiazomethyl radical. Electronic structure calculations have been performed at the B3LYP/6-311++G(d,p) level of theory to study the molecular structure of the ion. Equilibrium geometries of four possible conformers of the iminodiazomethyl anion have been obtained from the calculations. Spectral simulations have been performed on the basis of the calculated geometries and normal modes of these conformationally isomeric ions and the corresponding radicals. The spectral analysis suggests that the ions of two conformations are primarily formed in the aforementioned reaction. The relative abundance of the two conformers substantially deviates from the thermal equilibrium populations, and it reflects the potential energy surfaces relevant to conformational isomerization processes. The electron affinities of the ( ZE)- and ( EE)-iminodiazomethyl radicals have been determined to be 2.484 +/- 0.007 and 2.460 +/- 0.007 eV, respectively. The energetics of the iminodiazomethyl anion is compared with that of the most stable structural isomer, the 1,2,3-triazolide ion. Collision-induced dissociation of the 1,2,3-triazolide ion has also been studied in flowing afterglow-selected ion flow tube experiments. Facile fragmentation generating a product ion of m/ z 40 has been observed. DFT calculations suggest that fragmentation of the 1,2,3-triazolide ion to the cyanomethyl anion and N2 is exothermic. The stability of the ion is discussed in comparison with other azolide ions with different numbers of N atoms in the five-membered ring.     

Simple and effective 3D recognition of domoic acid using a molecularly imprinted polymer

We have developed a simple and effective molecular imprinting technique to target compounds with flexible structure. Domoic acid (DA), an amnesic shellfish poison, was used as the target compound while many acidic compounds (mono-, di-, and tricarboxylic acids) were used as template molecules for molecularly imprinted polymers (MIPs). Evaluation of selective recognition abilities using liquid chromatography revealed that the highest selective recognition ability for DA was found when pentane-1,3,5-tricarboxylic acid (1,3,5-PeTA) was used as the template. Computer modeling studies of the DA structure suggested that the observed selective recognition depended on the structural changes in DA at the recognition site of the MIPs as well as spatial distance between the COOH groups in DA and 1,3,5-PeTA. Using the 1,3,5-PeTA-MIP, we could easily purify DA from blue mussel extracts by solid-phase extraction.     

Structure of the vinyldiazomethyl anion and energetic comparison to the cyclic isomers

The 351.1 nm photoelectron spectrum of the vinyldiazomethyl anion has been measured. The ion is generated through the reaction of the allyl anion with N(2)O in helium buffer gas in a flowing afterglow source. The spectrum exhibits the vibronic structure of the vinyldiazomethyl radical in its electronic ground state as well as in the first excited state. Electronic structure calculations have been performed for these molecules at the B3LYP/6-311++G(d,p) level of theory. A Franck-Condon simulation of the X (2)A' state portion of the spectrum has been carried out using the geometries and normal modes of the anion and radical obtained from these calculations. The simulation unambiguously shows that the ions predominantly have an E conformation. The electron affinity (EA) of the radical has been determined to be 1.864 +/- 0.007 eV. Vibrational frequencies of 185 +/- 10 and 415 +/- 20 cm(-1) observed in the spectrum have been identified as in-plane CCN bending and CCC bending modes, respectively, for the X (2)A' state. The spectrum for the A (2)A' state is broad and structureless, reflecting large geometry differences between the anion and the radical, particularly in the CCN angle, as well as vibronic coupling with the X (2)A' state. The DFT calculations have also been used to better understand the mechanism of the allyl anion reaction with N(2)O. Collision-induced dissociation of the structural isomer of the vinyldiazomethyl anion, the 1-pyrazolide ion, has been examined, and energetics of the structural isomers is discussed.     

Superacid‐catalyzed Friedel–Crafts phosphination of 2‐hydroxybiphenyls with phosphorus trichloride

Cyclic phosphorus compounds, 6H‐dibenz[c,e][1,2]oxaphosphorin‐6‐oxide derivatives, were efficiently synthesized by the Friedel–Crafts reaction of 2‐hydroxybiphenyls with phosphorus trichloride in the presence of superacids, especially trifluoromethanesulfonic acid (TfOH) as a catalyst. TfOH was investigated for the first time as an effective catalyst for the aromatic phosphination of 2‐hydroxybiphenyls.     

Influence of Ar background gas pressure on composition and crystal orientation in PLD-Fe(Se1−xTex) thin films

Fe(Se_1?xTe_x) thin films on (1 0 0) SrTiO₃ were fabricated by a pulsed laser deposition method, and their crystal orientation, compositional shifts and superconducting properties were characterized by X-ray diffraction, scanning electron microscope combined with energy dispersive X-ray spectroscopy, etc. Compositional shift is one of the major problems during the fabrication of Fe(Se_1?xTe_x) films due to its containing high volatile elements such as Se and Te. The compositional shifts were found dependent on the Ar background gas pressure (P_Ar), which was suppressed by the increase of P_Ar. In addition, it was revealed that the temperature window for the crystallization of the films was shifted to higher temperature region and wider temperature range with the increase of P_Ar.