Insight into the pathway for biosynthesis of sesquarterpenes in nonpathogenic Mycobacterium species: identification of heptaprenylcycli-14E,18E-diene

A new sesquarterpene, heptaprenylcycli-14E,18E-diene, was isolated from Mycobacterium chlorophenolicum cells grown up to the stationary phase. The absence of heptaprenylcycli-14Z,18E-diene indicates that only (E,E,E)-geranylgeranyl diphosphate may be utilized as an intermediate of sesquarterpene biosynthesis in the stationary phase, in contrast with the logarithmic growth phase in which both (E,E)-farnesyl diphosphate and (E,E,E)-geranylgeranyl diphosphate are used. Further, our findings suggest that the stepwise reduction of the polyprenyl group in sesquarterpene biosynthesis might proceed in a different order from that in chlorophyll biosynthesis.     

Intermolecular Communication on a Liposomal Membrane: Enzymatic Amplification of a Photonic Signal with a Gemini Peptide Lipid as a Membrane‐Bound Artificial Receptor

A supramolecular system that can activate an enzyme through photo‐isomerization was constructed by using a liposomal membrane scaffold. The design of the system was inspired by natural signal transduction systems, in which enzymes amplify external signals to control signal transduction pathways. The liposomal membrane, which provided a scaffold for the system, was prepared by self‐assembly of a photoresponsive receptor and a cationic synthetic lipid. NADH‐dependent L ‐lactate dehydrogenase, the signal amplifier, was immobilized on the liposomal surface by electrostatic interactions. Recognition of photonic signals by the membrane‐bound receptor induced photo‐isomerization, which significantly altered the receptor’s metal‐binding affinity. The response to the photonic signal was transmitted to the enzyme by Cu²⁺ ions. The enzyme amplified the chemical information through a catalytic reaction to generate the intended output signal.     

Direct measurement of the laplace pressure in a very thin liquid film

Meniscus force plays an important part in magnetic storage devices, scanning probe microscopy, and micromachines, because the meniscus force increases steeply as the clearance between solid surfaces decreases down to submicrometers. Recently increased experimental and analytical studies on the subject have been published from the point of view of mechanical engineering. Meniscus force is generated by the Laplace pressure within the thin liquid film. Investigating the Laplace pressure is a direct way to clarify the generation mechanism of meniscus force. However, no appropriate measuring method of the Laplace pressure is available for a very thin liquid film confined by solid surfaces. This paper proposes a simple method of direct measurement of the Laplace pressure for the cases. The principle of the measurement method is described. Measurement is conducted using the measuring device. Experimental results on the Laplace pressure show good agreement with the theoretical predictions.     

Anodic oxidation of organic compounds based on the cation exchange reaction between KBF4 and solid-supported acids

We have developed a novel electrolytic system for anodic oxidation of organic compounds based on the cation exchange reaction between potassium tetrafluoroborate (KBF₄) and solid-supported acids. It was clarified by cyclic voltammetry as well as preparative electrolyses that hydrogen tetrafluoroborate (HBF₄) derived from the cation exchange reaction acts as a supporting electrolyte in MeCN. On the basis of the electrolytic system, anodic oxidation of 1,2,4-trimethoxybenzene was carried out to provide the corresponding homocoupling product in quantitative yield. Furthermore, anodic oxidation of benzyl alcohols having not only electron-donating but also electron-withdrawing groups at the para position was successfully achieved by optimizing the reaction conditions.     

Hexa‐ and Octagold Chains from Flexible Tetragold Molecular Units Supported by Linear Tetraphosphine Ligands

A flexible building block : Flexible tetragold(I) chain complexes supported by a new single methylene‐bridged tetraphosphine ligand were synthesized and further transformed into discrete linear octagold(I) {Au₈} and cyclic hexagold(I) {Au₆} structures by reaction with KI and NaAuCl₄, respectively (see picture, Au purple, Cl dark green, PF₆ light green, I pink). The tetragold complexes are also luminescent at room temperature.

     

Double Homologation Method for Substituted Soluble Pentacenes and Dimerization Behaviours of Pentacenes

Double up : A zirconium‐mediated double homologation method was successfully applied for the synthesis of multi‐substituted pentacene derivatives from 1,2,4,5‐tetrakis(propargyl)benzenes. The bis(zirconacyclopentadiene) intermediates were also characterized. Among these symmetrical derivatives, tetra‐ and octa‐substituted pentacenes undergo reversible conversion between monomeric and dimeric forms.

     

Formation of undulated lamellar structure from ABC block terpolymer blends with different chain lengths

The effect of molecular weight distribution of ABC linear terpolymers on the formation of periodic structures was investigated. Three poly(isoprene-b-styrene-b-2-vinylpridine) triblockterpolymers with molecular weights of 26k, 96k, and 150k were blended variously. Three-phase, four-layer lamellar structures were observed when polydispersity index (PDI) was low, but it has been found that simple lamellar structure with flat surface transforms into an undulated lamellar one, where two interfaces, i.e., I/S and S/P, are both undulated, and they are synchronizing each other if PDI exceeds the critical value. This new structure could be formed due to the periodic and "weak" localization of three chains along the domain interfaces, which produces periodic surfaces with nonconstant mean curvatures. With further increase of PDI, the blend macroscopically phase-separated into different microphase-separated structures.     

Rapid detection of nivalenol and deoxynivalenol in wheat using surface plasmon resonance immunoassay

A surface plasmon resonance (SPR) immunoassay using a monoclonal antibody was developed to measure nivalenol (NIV) and deoxynivalenol (DON) contamination in wheat. A highly sensitive and stable DON-immobilized sensor chip was prepared, and an SPR detection procedure was developed. The competitive inhibition assay used a monoclonal antibody that cross-reacts with NIV and DON. The half maximal inhibitory concentration (IC₅₀) values of the SPR assay were 28.8 and 14.9 ng mL⁻¹ for NIV and DON, respectively. The combined responses of NIV and DON in wheat were obtained using a simultaneous detection assay in a one-step cleanup procedure. NIV and DON were separated using a commercial DON-specific immunoaffinity column (IAC) and their responses were obtained using an independent detection assay. Spiked tests using these toxins revealed that recoveries were in the range 91.5-107% with good relative standard deviations (RSDs) (0.40-4.1%) and that detection limits were 0.1 and 0.05 mg kg⁻¹ for NIV and DON, respectively. The independent detection using IAC showed detection limits of 0.2 and 0.1 mg kg⁻¹ for NIV and DON, respectively. SPR analysis results were correlated with those obtained using a conventional LC/MS/MS method for wheat co-contaminated with NIV and DON. These results suggested that the developed SPR assay is a practical method to rapidly screen the NIV and DON co-contamination of wheat and one of a very few immunoassays to detect NIV directly.     

Synthesis of metal-hydrazone complexes and vapochromic behavior of their hydrogen-bonded proton-transfer assemblies

We synthesized and investigated a new series of metal-hydrazone complexes, including deprotonated [MX(mtbhp)] and protonated forms [MX(Hmtbhp)](ClO(4)) (M = Pd(2+), Pt(2+); X = Cl(-), Br(-); Hmtbhp = 2-(2-(2-(methylthio)benzylidene)hydrazinyl)pyridine) and hydrogen-bonded proton-transfer (HBPT) assemblies containing [PdBr(mtbhp)] and bromanilic acid (H(2)BA). The mtbhp hydrazone ligand acts as a tridentate SNN ligand and provides a high proton affinity. UV-vis spectroscopy revealed that these metal-hydrazone complexes follow a reversible protonation-deprotonation reaction ([MX(mtbhp)] + H(+) ? [MX(Hmtbhp)](+)), resulting in a remarkable color change from red to yellow. Reactions between proton acceptor [PdBr(mtbhp)] (A) and proton donor H(2)BA (D) afforded four types of HBPT assemblies with different D/A ratios: for D/A = 1:1, {[PdBr(Hmtbhp)](HBA)·Acetone} and {[PdBr(Hmtbhp)](HBA)·2(1,4-dioxane)}; for D/A = 1:2, [PdBr(Hmtbhp)](2)(BA); and for D/A = 3:2, {[PdBr(Hmtbhp)](2)(HBA)(2)(H(2)BA)·2Acetonitrile}. The proton donor gave at least one proton to the acceptor to form the hydrogen bonded A···D pair of [PdBr(Hmtbhp)](+)···HBA(-). The strength of the hydrogen bond in the pair depends on the kind of molecule bound to the free monoanionic bromanilate OH group. Low-temperature IR spectra (T < 150 K) showed that the hydrogen bond distance between [PdBr(Hmtbhp)](+) and bromanilate was short enough (ca. 2.58 ?) to induce proton migration in the [PdBr(Hmtbhp)](2)(BA) assembly in the solid state. The hydrogen bonds formed not only between [PdBr(Hmtbhp)](+) and HBA(-) but also between HBA(-) and neutral H(2)BA molecules in the {[PdBr(Hmtbhp)](2)(HBA)(2)(H(2)BA)·2Acetonitrile} assembly. The H(2)BA-based flexible hydrogen bond network and strong acidic host structure result in an interesting vapor adsorption ability and vapochromic behavior in this assembly because the vapor-induced rearrangement of the hydrogen bond network, accompanied by changes in π-π stacking interactions, provides a recognition ability of proton donating and accepting properties of the vapor molecule.