Glucose and lactate biosensors prepared by a layer-by-layer deposition of concanavalin A and mannose-labeled enzymes: electrochemical response in the presence of electron mediators.

An electrochemical response of glucose and lactate biosensors which were prepared by coating a platinum electrode with a thin film composed of concanavalin A and mannose-labeled glucose oxidase (GOx) or lactate oxidase (LOx) was evaluated in the presence of ferrocene derivatives as electron mediator. Both glucose and lactate biosensors showed catalytic current to glucose and lactate, respectively, in cyclic voltammetry, suggesting that the ferrocene derivatives can mediate electron transport smoothly from the reduced forms of GOx and LOx in the thin films to the electrode. Among the three kinds of ferrocene derivatives used, ferrocenylmethanol was found to be the most suitable electron mediator because of its low oxidation potential. The glucose and lactate sensors gave useful calibration graphs, in which higher detection limits were reached as compared with those observed when the sensors were operated in the absence of electron mediator.     

Amphidinolides T2, T3, and T4, new 19-membered macrolides from the dinoflagellate Amphidinium sp. and the biosynthesis of amphidinolide T1.

Three new 19-membered macrolides, amphidinolides T2 (2), T3 (3), and T4 (4), structurally related to amphidinolide T1 (1) have been isolated from two strains of marine dinoflagellates of the genus Amphidinium. The structures of 2-4 were elucidated on the basis of spectroscopic data. The absolute configurations at C-7, C-8, and C-10 of 1-4 were determined by comparison of NMR data of their C-1-C-12 segments with those of synthetic model compounds for the tetrahydrofuran portion. The biosynthetic origins of amphidinolide T1 (1) were investigated on the basis of 13C NMR data of a 13C enriched sample obtained by feeding experiments with [1-(13)C], [2-(13)C], and [1,2-(13)C2] sodium acetates and 13C-labeled sodium bicarbonate in the cultures of the dinoflagellate. These incorporation patterns suggested that amphidinolide T1 (1) was generated from four successive polyketide chains, an isolated C1 unit formed from C-2 of acetates, and three unusual C2 units derived only from C-2 of acetates. Furthermore, it is noted that five oxygenated carbons of C-1, C-7, C-12, C-13, and C-18 were not derived from the C-1 carbonyl, but from the C-2 methyl of acetates.     

Trapping of 1,8-biradical intermediates by molecular oxygen in photocycloaddition of naphthyl-N-(naphthylcarbonyl)carboxamides; formation of novel 1,8-epidioxides and evidence of stepwise aromatic cycloaddition.

The photocycloaddition reaction of naphthyl-N-(naphthylcarbonyl)carboxamides (1) was examined under argon and oxygen atmospheres. In addition to the [2 + 2] and [4 + 4] cycloadducts, 3 and 4, respectively, novel 1,8-epidioxides (5) were formed under oxygen atmosphere. The transient absorption at lambda max of 360 nm with the lifetime of 360 ns was observed by laser flash photolysis of 1c and was interpreted as the absorption of biradical intermediate 2. On the basis of the anti stereochemistry of 5, which was different from that of the major [4 + 4] cycloadducts, syn-4, it was deduced that equilibrium between biradical intermediates syn-2 and anti-2 would exist. Retro [2 + 2] cycloaddition of 3 was responsible for the efficient trapping of the biradical intermediate with molecular oxygen. The photocycloaddition of the anthryl derivatives, 9-anthryl-N-(methylethyl)-N-(naphthylcarbonyl)carboxamides (7), afforded the [4 + 4] cycloadducts (8) exclusively in a quantitative yield even under oxygen atmosphere. The absence of trapping with molecular oxygen was interpreted to be due to the lack of retro [4 + 4] cycloaddition of 8.     

Experimental study of underwater rock drilling using a pulsed Ho:YAG laser-induced jets

This paper is primarily an assessment of laser-induced water jets for boring rock surfaces. It also reports the result of preliminary experiments of pulsed Ho:YAG laser-induced jets applied to drill a submerged rock specimen. The irradiation of pulsed Ho:YAG laser beams at 3 Hz inside a thin metal tube produces intermittent water vapor bubbles which result in liquid jet discharge from the exit of the metal tube. The laser-induced water jets are visualized by shadowgraphs and images are recorded by a high-speed digital video camera. High stagnation pressures were eventually generated by the jet impingements. Simultaneously shock waves of about 22.7 MPa were generated at bubble collapse, which effectively cracked the surface of the rock specimens. Repeated exposures of these laser-induced jets against submerged rock specimens have a potential to practically bore holes on rock surfaces.     

First observation of the P-wave spin-singlet bottomonium states hb(1P) and hb(2P)

We report the first observations of the spin-singlet bottomonium states h(b)(1P) and h(b)(2P). The states are produced in the reaction e(+)e(-)→h(b)(nP)π(+)π(-) using a 121.4 fb(-1) data sample collected at energies near the Υ(5S) resonance with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider. We determine M[h(b)(1P)]=(9898.2(-1.0-1.1)(+1.1+1.0)) MeV/c(2) and M[h(b)(2P)]=(10,259.8±0.6(-1.0)(+1.4)) MeV/c(2), which correspond to P-wave hyperfine splittings ΔM(HF)=(+1.7±1.5) and (+0.5(-1.2)(+1.6)) MeV/c(2), respectively. The significances of the h(b)(1P) and h(b)(2P) are 5.5σ and 11.2σ, respectively. We find that the production of the h(b)(1P) and h(b)(2P) is not suppressed relative to the production of the Υ(1S), Υ(2S), and Υ(3S).     

Pyrrole-Based π-System–PtII Complexes: Chiroptical Properties and Excited-State Dynamics with Microsecond Triplet Lifetimes

Heteroleptic Pt^II complexes comprising π-extended dipyrrins and 2-phenylquinoline were prepared. Single-crystal X-ray analysis disclosed the stepped conformations of two ligand moieties in these Pt^II complexes. The enantiomers could be separated by HPLC and their configurations were determined from CD spectroscopy results and TD-DFT calculations. Transient absorption measurements revealed excited-state dynamics characterized by fast intersystem crossing and microsecond-order triplet-state lifetimes.     

Atomically Precise Alloy Nanoclusters

Metal nanoclusters (NCs) have a particle size of about one nanometer, which makes them the smallest unit that can give a function to a substance. In addition, metal NCs possess physical and chemical properties that are different from those of the corresponding bulk metals. Metal NCs with such characteristics are expected to be important for use in nanotechnology. Research on the precise synthesis of metal NCs and elucidation of their physical/chemical properties and functions is being actively conducted. When metal NCs are alloyed, it is possible to obtain further various electronic and geometrical structures and functions. Thus, research on alloy NCs has become a hot topic in the study of metal NCs and the number of publications on alloy NCs has increased explosively in recent years. Such publications have provided much insight into the effects of alloying on the electronic structure and function of metal NCs. However, the rapid increase in knowledge has made it difficult for researchers (especially those new to the field) to grasp all of it. Therefore, in this review, we summarize the reported chemical composition, geometrical structure, electronic structure, and physical and chemical properties of Au_n−xM_x(SR)_m, Ag_n−xM_x(SR)_m, Au_n−xM_x(PR₃)_l(SR)_m, and Ag_n−xM_x(PR₃)_l(SR)_m (Au=gold, Ag=silver, M=heteroatom, PR₃=phosphine, and SR=thiolate) NCs. This review is expected to help researchers understand the characteristics of alloy NCs and lead to clear design guidelines to develop new alloy NCs with intended functions.     

Double-Gyroid Nanostructure Formation by Aggregation-Induced Atropisomerization and Co-Assembly of Ionic Liquid-Crystalline Amphiphiles

We report a new molecular-design principle for creating double-gyroid nanostructured molecular assemblies based on atropisomerization. Ionic amphiphiles containing two imidazolium rings close to each other were designed and synthesized. NMR data revealed that the rotation of the imidazolium rings is restricted, with an activation energy as high as 63 kJ mol⁻¹ in DMSO-d₆ solution (DFT prediction for a model compound in the vacuum: 90–100 kJ mol⁻¹). Due to the restricted rotation, the amphiphiles feature “double” atropisomeric axes in their ionic segments and form three stable atropisomers: meso, R, and S. These isomers co-organize into -type bicontinuous cubic liquid-crystalline mesophases through nanosegregation of the ionic and non-ionic parts. Considering the intrinsic characteristic of -type bicontinuous cubic structures that they are composed of intertwined right- and left-handed single gyroids, we propose that the simultaneous presence of both R- and S-atropisomers is an important contributor to the formation of double-gyroid structures.