[Single-Laboratory Validation Study of Determination of Patulin by GC-MS in Juice].

We examined whether the analytical method of patulin (a mycotoxin found in fruit juice) developed in Nagano prefecture meets the criteria in the Codex Procedural Manual and Guidelines on Analytical Terminology. The trueness, repeatability, within-laboratory reproducibility and HorRat value were 98.8-103.4%, less than 6.4, 8.1 and 0.4%, respectively, for apple juice and pear juice.Thus, the trueness and precision met the required criteria.

Characterization of a novel DyP-type peroxidase from Streptomyces avermitilis.

DyP-type peroxidases are a heme peroxidase family with unique properties whose members are widely distributed from prokaryotes to eukaryotes. DyP-type peroxidases are subdivided into class P, I and V based on structure-based sequence alignment. Class V enzymes possess degradation activities for anthraquinone dyes, and include extra sequences compared with class P and I. Class V enzymes are mainly found in fungi, with only two such proteins, AnaPX and DyP2, reported in bacteria. Here, we heterologously expressed, purified and biochemically characterized SaDyP2 protein, predicted to belong to class V. SaDyP2 was purified as a ∼50 kDa enzyme containing a heme cofactor and was found to oxidize the typical peroxidase substrates, ABTS and DMP. SaDyP2 was generally thermostable and exhibited a lower optimal pH, a feature typical of DyP-type peroxidases. It also degraded anthraquinone dyes, a specific substrate of DyP-type peroxidases, although the kcat for SaDyP2 was lower than that for other class V enzymes. The Km value of SaDyP2 for anthraquinone dye was similar to that of other enzymes of this class. Homology modeling revealed that the structure of SaDyP2 best fit that of class V enzymes.

Selective formation of twisted intramolecular charge transfer and excimer emissions on 2,7-bis(4-diethylaminophenyl)-fluorenone by choice of solvent.

We designed and synthesized a donor-acceptor-donor dye consisting of a 2,7-disubstituted fluorenone with diethylaminophenyl moieties present as strong electron donating groups. Switching between twisted intramolecular charge transfer (TICT) emission and excimer emission was achieved, with no ground state changes, by simply changing the solvent used. In a nonpolar solvent, excimer emission was observed; with increasing polarity, the emission gradually disappeared, and the TICT emission appeared.