Yasumasa Fukushima

Colorimetric chemosensor for ATP based on phthalimide-appended poly(2,5-dimethoxyaniline)

We have designed a colorimetric conjugated polymer (PDMAp) for selective ATP sensing based on poly(2,5-dimethoxyaniline) bearing phthalimide which can form hydrogen bonds with adenine. PDMAp have been synthesized via chemical oxidative polymerization with CSA and DDQ and dedoping with an aqueous ammonia solution. PDMAp was displayed to signal the colorimetric selective detection for ATP over various nucleotides such as ADP, AMP, CTP, TTP, and GTP in DMSO–water (9:1, v/v) mixture. The absorption spectral change can be attributed to a doping process of ATP to PDMAp through hydrogen bonds between phthalimide and adenine as well as electrostatic interactions between the phosphate group of ATP and the backbone of PDMAp.

Colorimetric detection of oxalate in aqueous solution by a pyrogallol red‐based Cu2+ complex

The pyrogallol red (PR)-based Cu2+ complex was proven to be an effective and selective colorimetric chemosensing ensemble for recognition of oxalate over other anions in a perfect aqueous solution. The addition of oxalate to the PR-Cu2+ complex resulted in a colour change from purple to orange colour due to the regeneration of PR by the chelation of oxalate with Cu2+ , while other anions did not induce any significant colour change. Moreover, it was revealed that no obvious interference was observed during the titrations with oxalate into each other anion. Therefore, the PR-Cu2+ complex can be used as a simple and practical colorimetric chemosensor for detecting oxalate.

Colorimetric chemosensor based on a carminic acid and Pb 2+ complex for selective detection of cysteine over homocysteine and glutathione in aqueous solution

We have developed a colorimetric chemosensor for the selective and sensitive detection of Cys based on the complex (CA-2Pb2+) between a commercially available natural organic dye, carminic acid (CA) and Pb2+ in pure aqueous solution at physiological pH. The addition of Cys to the CA-2Pb2+ solution resulted in a distinct color change from purple to red together with a remarkable absorption spectral change by the restoration of CA through a displacement mechanism with formation of the Cys-Pb2+ complex, whereas other amino acids and glutathione induce no or minimal spectral and color changes. Moreover, the other amino acids and GSH do not affect the detection ability of CA-2Pb2+ for Cys. The reversibility even through several cycles was established for practical applications. The results indicate that CA-2Pb2+ may be useful as a potential colorimetric and naked-eye chemosensor for Cys over Hcy and GSH in aqueous solution.

Colorimetric chemosensor for Fe2+ and Fe3+ based on a ternary mixture of an anionic dye, a cationic polyelectrolyte, and a metal chelator in aqueous solution

A new colorimetric chemosensor based on a simple ternary mixture of an anionic dye, pyrogallol red (PR), a cationic polyelectrolyte, poly(diallyldimethylammonium chloride) (PDADMAC), and a metal chelator, N-(2-hydroxyethyl) ethylenediaminetriacetic acid (HEDTA) for the colorimetric detection of Fe2+ and Fe3+ has been developed in an aqueous solution buffered at pH 5. Upon addition of Fe2+ or Fe3+ to the mixture, the absorption spectra showed a bathochromic shift; correspondingly, the solution color changed from red to blue, whereas other metal ions basically resulted in insignificant spectral and color changes. From the competitive experiments, no obvious interferences for the colorimetric detection of Fe2+ and Fe3+ were observed in the presence other metal ions. The results indicated that the mixture could be used as a potential Fe2+ and Fe3+ colorimetric and naked eye chemosensor in aqueous media. This research demonstrates that the ternary ensemble consisted of an organic dye, an oppositely charged polyelectrolyte, and a metal chelator is a versatile and convenient tool for the facile preparation of a novel chemosensor system.

Colorimetric Determination of Pb 2+ in Perfect Aqueous Solution Using Carminic Acid as a Selective Chemosensor

The commercially available natural organic dye, carminic acid (CA), an anthraquinone derivative bearing hydroxyl and carboxyl groups as recognition sites was found to be a colorimetric probe for Pb2+ in perfect aqueous solution under neutral conditions with specific selectivity and high sensitivity. Upon addition of Pb2+, the absorption maximum of CA showed a large red shift, and the resulted color change from red to purple could be easily identified even by the naked eye. The chemical stoichiometric ratio between CA and Pb2+ was determined to be 1:2 through Job plot, Pb2+ titration, and kinetic experiments. Moreover, other environmental relevant metal ions induced no or minimal spectral and color changes. The reversibility of Pb2+ to CA with EDTA even through several cycles was established for practical applications. The results indicated that CA can be a good candidate for simple, convenient and reversible colorimetric detection of Pb2+ in aqueous solution even though it was hard to be applied to determine Pb2+ on the water testing by US EPA.

Salinarchaeum chitinilyticum sp. nov., a chitin-degrading haloarchaeon isolated from commercial salt

Two chitin-degrading halophilic archaeal strains, MC-74T and MC-23, were isolated from commercial salt samples. Cells were motile, rod-shaped and stained Gram-negative. Colonies were vermillion-pigmented. Strains MC-74T and MC-23 were able to grow with 1.5-5.1 M NaCl (optimum, 2.6-3.1 M) at pH 6.0-10.0 (optimum, pH 7.0) and at 20-50 °C (optimum, 40 °C). The orthologous 16S rRNA gene sequence similarity between the two strains was 99.8 %, and the closest phylogenetic relative was Salinarchaeum laminariae JCM 17267T with 99.3-99.5 % similarity. The level of DNA-DNA relatedness between the two strains was 93 and 94 % (reciprocally), and those between the two strains and Salinarchaeumlaminariae JCM 17267T were 35-36 % and 38-39 % (reciprocally). The polar lipids of both strains were phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester and phosphatidylglycerol sulfate. Glycolipids were not detected. Based on the phenotypic and phylogenetic analyses, the strains represent a novel species of the genus Salinarchaeum, for which the name Salinarchaeum chitinilyticum sp. nov. is proposed. The type strain is MC-74T (=JCM 19597T=KCTC 4262T), isolated from solar salt produced in France. Strain MC-23, isolated from a commercial solar salt sample produced in China, is an additional strain of the species.