High-performance liquid chromatography with fluorescence detection for the simultaneous determination of 3,4-methylenedioxymethamphetamine, methamphetamine and their metabolites in human hair using DIB-Cl as a label

This paper describes a highly sensitive HPLC method for the simultaneous determination of 3,4-methylenedioxymethamphetamine (MDMA), 3,4-methylenedioxyamphetamine (MDA), amphetamine (AP) and methamphetamine (MP) in human hair samples. The amphetamines investigated were derivatized with the fluorescent reagent, DIB-Cl to yield highly fluorescent DIB-derivatives, which were then analyzed by HPLC with fluorescence detection at excitation and emission wavelengths of 325 nm and 430 nm, respectively. The separation was achieved on an ODS column with an isocratic mobile phase composed of acetonitrile-methanol-water (30:40:30, v/v/v). The limits of detection for the four compounds obtained by the proposed method ranged from 11 to 200 pg/mg. The method was successfully applied to the determination of MDMA and MDA in hair samples obtained from MDMA abuser.     

Reversing the Handedness of Self‐Assembled Porous Molecular Networks through the Number of Identical Chiral Centres

Scanning tunnelling microscope observations at the 1‐phenyloctane/graphite interface reveal how chiral structural information at the molecular level is transferred and expressed structurally at the 2D supramolecular level for a porous system. The chirality of self‐assembled molecular networks formed by chiral dehydrobenzo[12]annulene (cDBA) derivatives having three chiral chains and three achiral chains, alternatingly, is compared with those of cDBAs having six chiral chains reported previously. While for all cDBAs homochiral surfaces are formed, their handedness is not simply a reflection of the absolute configuration of the stereogenic centres. Both the number of stereogenic centres as well as the length of the achiral chains determine the supramolecular handedness, providing a deep insight into the supramolecular chirality induction mechanisms at play. Moreover, these cDBAs act to induce chirality in porous networks formed by achiral DBAs.     

Determination of a new type of phosphodiesterase-5 inhibitor, thioquinapiperifil, in a dietary supplement promoted for sexual enhancement

A new type of phosphodiesterase-5 (PDE-5) inhibitor, thioquinapiperifil (1), was found in dietary supplements. LC-MS analysis indicated that the supplements contain two major compounds. One was identified as thiodenafil (synonym: thiosildenafil) by direct comparison with the authentic compound. The other showed a molecular weight of 448, and accurate mass measurement showed its elemental composition to be C(24)H(28)N(6)O(1)S(1). Together, the mass and NMR spectrometric data revealed that the compound is an imidazoquinazoline derivative: 3-ethyl-1,3-dihydro-8-[[[2-[4-(hydroxymethyl)-1-piperidinyl]phenyl]methyl]amino]-2H-imidazo[4,5-g]quinazoline-2-thione. This compound had been synthesized as a PDE-5 inhibitor, formerly reported as KF31327 by Kyowa Hakko Kogyo Co., Ltd. Considering this compound's general properties, it has been renamed thioquinapiperifil with the agreement of Kyowa Hakko Kogyo Co., Ltd. The detection of imidazoquinazoline-type compounds in dietary supplements has not been reported. Quantitative analysis showed that the contents of 1 and thiodenafil in the products were about 13-15 mg/tablet (43-48 microg/mg) and about 0.4 mg/tablet (1 microg/mg), respectively.     

Effects of the extensional rate on two-dimensional turbulence of semi-dilute polymer solution flows

An experimental study has been performed to investigate the relationship between the extensional viscosity of polymers and the turbulent drag reduction. In order to obtain the flow which is mostly dominated by extensional flow, two-dimensional (2D) grid turbulence made by flowing soap films was used. Extensional rate added to the flow was controlled by changing the conformation of the grid. Polyethylene oxide, as a flexible polymer, and hydroxypropyl cellulose, as a rigid rod-like polymer were added to the flow. Several extensional rates affect polymer behaviors, which induce different effects. Drag reduction effects of polymers under several extensional rates were visualized and analyzed by image processing. Rheological properties of the polymer solutions were also measured by a rheometer. The results indicated that the mechanisms of energy transfer are different in the streamwise and normal directions. The critical concentration to observe drag reduction effects in 2D turbulence was changed by the extensional rate. When extensional rate is higher, the effects were started to observe from lower concentration. These results were confirmed to correspond to the drag reduction effects obtained by classical pressure drop experiments in a pipe flow.     

Quantum Dynamics and Kinematics from a Statistical Model Selected by the Principle of Locality

Quantum mechanics predicts correlation between spacelike separated events which is widely argued to violate the principle of local causality. By contrast, here we shall show that the Schrödinger equation with Born’s statistical interpretation of wave function and uncertainty relation can be derived from a statistical model of microscopic stochastic deviation from classical mechanics which is selected uniquely, up to a free parameter, by the principle of Local Causality. Quantization is thus argued to be physical and Planck constant acquires an interpretation as the average stochastic deviation from classical mechanics in a microscopic time scale. Unlike canonical quantization, the resulting quantum system always has a definite configuration all the time as in classical mechanics, fluctuating randomly along a continuous trajectory. The average of the relevant physical quantities over the distribution of the configuration are shown to be equal numerically to the quantum mechanical average of the corresponding Hermitian operators over a quantum state.     

β-d-Xylosidase from Geobacillus thermoleovorans IT-08: Biochemical Characterization and Bioinformatics of the Enzyme

The gene encoding a thermostable β-d-xylosidase (GbtXyl43B) from Geobacillus thermoleovorans IT-08 was cloned in pET30a and expressed in Escherichia coli; additionally, characterization and kinetic analysis of GbtXyl43B were carried out. The gene product was purified to apparent homogeneity showing M _r of 72 by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The enzyme exhibited an optimum temperature and pH of 60 °C and 6.0, respectively. In terms of stability, GbtXyl43B was stable at 60 °C at pH 6.0 for 1 h as well as at pH 6–8 at 4 °C for 24 h. The enzyme had a catalytic efficiency (k _cat/K _M) of 0.0048?±?0.0010 s^?1 mM^?1 on p-nitrophenyl-β-d-xylopyranoside substrate. Thin layer chromatography product analysis indicated that GbtXyl43B was exoglycosidase cleaving single xylose units from the nonreducing end of xylan. The activity of GbtXyl43B on insoluble xylan was eightfold higher than on soluble xylan. Bioinformatics analysis showed that GbtXyl43B belonging to glycoside hydrolase family 43 contained carbohydrate-binding module (CBM; residues 15 to 149 forming eight antiparallel β-strands) and catalytic module (residues 157 to 604 forming five-bladed β-propeller fold with predicted catalytic residues to be Asp287 and Glu476). CBM of GbtXyl43B dominated by the Phe residues which grip the carbohydrate is proposed as a novel CBM36 subfamily.