Naoko Iwasawa

Phase transition of tetrakis(octylthio)tetrathiafulvalene (TTC8–TTF) and crystal structure analysis

Tetrakis(octylthio)tetrathiafulvalene (TTC8–TTF) crystallizes into two different phases (Forms I and II). Form I undergoes a slightly endothermic, phase transition at ca. 33 °C with a steep increase in the resistivity and a decrease in the drift mobility. Powder X-ray diffraction confirms that this transition is the result of a structural transformation from Form I to Form II. The microscopic origin of the phase transition is ascribed to a subtle repulsive motion in the nearest-neighbour octyl chains which results in the decrease in the transfer integrals between the neighbouring π-electron moieties of TTC8–TTF molecules within a segregated column.

A Fluorous Biphasic Solvent Extraction System for Lanthanides with a Fluorophilic β-Diketone Type Extractant

The properties of a fluorous solvent extraction system for trivalent lanthanide metal ions are reported. A fluorinated extractant, 4,4,5,5,6,6,7,7,8,8,9,9,9-tridecafluoro-1-(2-thienyl)-1,3-nonanedione, and HFE-7200 (C4F9OC2H5) as the extraction solvent were chosen. With this fluorous extractant/solvent combination, higher extraction ratios and separation factors compared to a conventional organic solvent system (thenoyltrifluoroacetone in CHCl3) were achieved for 5 heavy lanthanide ions (Lu, Yb, Tm, Er and Ho). On the other hand, light lanthanide ions (Nd, Pr, Ce and La) are hardly extracted, therefore enabling the mutual separation of light lanthanides from middle or heavy lanthanide ions.

Syntheses, Structures, and Thermal, Transport and Nonlinear Optical Properties of Tyc -Txf Compounds

Abstract The syntheses, electric and structural properties of a series of uncapped C6X4Y4 compounds (tetrakis(n-alkylchalcogeno)- tetrachalcogenafulvalenes; TYC -TXF) and nonlinear electric and optical properties of their CTn complexes are described.

Real-time monitoring and detection of primer generation-rolling circle amplification of DNA using an ethidium ion-selective electrode

An electrochemical detection system for an isothermal DNA amplification method using an ion-selective electrode (ISE) was developed as a low-cost, simple and real-time monitoring system. The system is based on potentiometry using an ethidium ion (Et(+)) selective electrode that relies on monitoring DNA amplification by measuring potential changes in the reaction solution containing ethidium bromide (EtBr) as an intercalator to DNA. With progressing primer generation-rolling circle amplification (PG-RCA) under isothermal condition at 37°C, EtBr is bound to the newly formed DNA, resulting in a lowered free EtBr concentration in the sample solution. In this case, the Et(+) ISE potential allows real-time monitoring of the PG-RCA reaction in the range of 10 nM - 1 μM initial target DNA.

Azide- and Dye-Conjugated Coelenterazine Analogues for a Multiplex Molecular Imaging Platform

Native coelenterazine (nCTZ) is a common substrate to most marine luciferases and photoproteins. In this study, nine novel dye- and azide-conjugated CTZ analogues were synthesized by conjugating a series of fluorescent dyes or an azide group to the C-2 or C-6 position of the nCTZ backbone to obtain bulkiness-driven substrate specificity and potential chemiluminescence/bioluminescence resonance energy transfer (C/BRET). The investigation on the optical properties revealed that azide-conjugated CTZs emit greatly biased bioluminescence to ALucs and ca. 130 nm blue-shifted bioluminescence with RLuc8.6 in living animal cells or lysates. The corresponding kinetic study explains that azide-conjugated CTZ exerts higher catalytic efficiency than nCTZ. Nile red-conjugated CTZ completely showed red-shifted CRET spectra and characteristic BRET spectra with artificial luciferase 16 (ALuc16). No or less spectral overlap occurs among [Furimazine-NanoLuc], [6-N3-CTZ-ALuc26], [6-pi-OH-CTZ-RLuc8.6], and [6-N3-CTZ-RLuc8.6] pairs, because of the substrate-driven luciferase specificity and color shifts, providing a crosstalk-free multiplex bioassay platform. The unique bioluminescence system appends a new toolbox to bioassays and multiplex molecular imaging platforms. This study is the first example that systematically synthesized fluorescent dye-conjugated CTZs and applied them for a bioluminescence assay system.

Steric hindrance effects in tripodal ligands for extraction and back-extraction of Ag+

A novel series of tripodal ligands with thiophenylether arms connected to an anchoring nitrogen has been investigated. Seven tripodal ligands were synthesized by combining methyl, isopropyl, and tert-butyl residue bearing thiophenylether sites as groups with different steric hindrance effects. The tripodal ligands allowed for the extraction of Ag+ ions from the aqueous phase into a chloroform phase by forming 1 : 1 complexes with Ag+. Back-extraction was performed with 1 M HNO3 aqueous solution. Each ligand showed different extraction and back-extraction efficiency for Ag+, affected by changes in steric hindrance caused by the various combinations of sidearms. These results are further supported by X-ray single crystal structural analysis.