Simultaneous determination of charge number and diffusion coefficient of 2-chloro-1,4-dimethoxybenzene in acetonitrile using potential-step chronoamperometry

Potential-step chronoamperometry using a microdisk electrode was carried out for the simultaneous determination of the charge number and diffusion coefficients of natural electron-mediator dimethoxybenzene analogues during electro-oxidation. The process was verified as a one-electron oxidation during the radical cation formation.     

Strong convergence of averaging iterations of nonexpansive nonself-mappings

Let C be a closed convex subset of Hilbert space H, T a nonexpansive nonself-mapping from C into H, and x₀,x,y₀,y elements of C. In this paper, we study the convergence of the two sequences generated by

     

Strategy for enantio- and diastereoselective syntheses of all possible stereoisomers of 1,3-polyol arrays based on a highly catalyst-controlled epoxidation of alpha,beta-unsaturated morpholinyl amides: application to natural product synthesis

We describe a new strategy for enantio- and diastereoselective syntheses of all possible stereoisomers of 1,3-polyol arrays. This strategy relies on a highly catalyst-controlled epoxidation of alpha,beta-unsaturated morpholinyl amides promoted by the Sm-BINOL-Ph(3)As[double bond]O (1:1:1) complex, followed by a conversion of morpholinyl amides into ketones and diastereoselective ketone reduction. Highly enantio- (up to >99 % ee) or diastereoselective (up to >99.5:0.5) epoxidation was achieved using 5-10 mol % of the Sm complex to afford synthetically very useful, nearly optically pure alpha,beta-epoxy morpholinyl amides. Stereoselectivity of the epoxidation was controlled by the chirality of BINOL with overwhelming inherent diastereofacial preference for the substrate. Combination with the syn- and anti-selective ketone reduction with the highly catalyst-controlled epoxidation allowed for an iterative strategy for the syntheses of all possible stereoisomers of 1,3-polyol arrays. Eight possible stereoisomers of 1,3,5,7-tetraol arrays were synthesized with high to excellent stereoselectivity. Moreover, the efficiency of the present strategy was successfully demonstrated by enantioselective syntheses of several 1,3-polyol/alpha-pyrone natural products, for example, cryptocaryolone diacetate.     

Solvent-dependent crystallization of 1-hydro-6-carbaphosphatrane and its tautomer

1-Hydro-6-carbaphosphatrane 2 was obtained as a mixture with its tautomer, 3. Tautomers 2 and 3 were isolated by the recrystallization from different solvents, respectively, and each structure was determined by X-ray crystallographic analysis. Variable-temperature NMR experiments revealed that pentacoordinate 2 and tricoordinate 3 are under the equilibrium, showing that 3 is more stable. The theoretical calculations found a weaker transannular PC bond in 2 than in 1-hydro-5-carbaphosphatrane, 1, which can be considered to be the reason 1-hydro-6-carba-phosphatrane 2 is less stable than its tautomer 3.     

Circadian gating of photoinduction of commitment to cell-cycle transitions in relation to photoperiodic control of cell reproduction in Euglena

A novel type of circadian and photoperiodic control of the cell division cycle was found in photoautotrophic Euglena gracilis. When algae entrained to 24 h light-dark (LD) cycles (14 h L) were transferred to continuous darkness (DD) at the eighth hour of the final LD photoperiod, cell-cycle transition was arrested in phase G1, S or G2. The subsequent exposure of these dark-arrested cells to a 6 h light-break allowed the dark-arrested cells to undergo cell-cycle progression in DD, in a manner dependent on the circadian phase; maximum photoinduction occurred around dusk. Inhibitor experiments suggested that the photoinduced commitment of G2 cells to cell division required light for a signal originating in noncyclic photosynthetic electron transport (PET), particularly cytochrome b6-f but not for the metabolic energy required by the process. The fact that the circadian rhythm of photoinduction ran out-of-phase from that of noncyclic PET signaling suggests that the site of regulation by the former rhythm is downstream of noncyclic PET. The occurrence of maximum photoinduction around dusk suggests that the 'external coincidence' model of photoperiodic induction describes the activation of the photoinductive phase. Further evidence supporting this hypothesis is the relationship between cell reproduction and day length; the resulting sigmoidal curve indicates a combined effect of photosynthesizing period and circadian stimulation around dusk. Circadian control is shown to be an integral part of the mechanism for 24 h LD cycle-induced synchronous cell division.     

Effects of chemically induced contraction of a coordination polyhedron on the dynamical magnetism of bis(phthalocyaninato)disprosium, a single-4f-ionic single-molecule magnet with a Kramers ground state

Chemically induced longitudinal contraction of the square-antiprism coordination polyhedron of a peripherically substituted bis(phthalocyaninato)dysprosiumate(III), a dysprosium-based single-4f-ionic single-molecule magnet having a J z = +/- (13)/ 2 Kramers doublet ground state, resulted in drastic changes in dynamical magnetism including a doubling of the energy barrier, a 2-order-of-magnitude decrease of the spin reversal rate, a significant rise of the blocking temperature, and the first observation of the emergence of a large remanent magnetization.     

Telomestatin-induced stabilization of the human telomeric DNA quadruplex monitored by electrospray mass spectrometry

Electrospray mass spectrometry (ESI-MS) was used to monitor the kinetics of duplex formation between the human telomeric DNA quadruplex and its complementary strand; the complexation of telomestatin to the G-quadruplex delays the unwinding of the quadruplex structure and formation of the duplex.     

A Water-Gated Organic Thin-Film Transistor for Glyphosate Detection: A Comparative Study with Fluorescence Sensing

This work reports the design of a highly sensitive solid-state sensor device based on a water-gated organic thin-film transistor (WG-OTFT) for the selective detection of herbicide glyphosate (GlyP) in water. A competitive assay among carboxylate-functionalized polythiophene, Cu²⁺, and GlyP was employed as a sensing mechanism. Molecular recognition phenomena and electrical double layer (EDL) (at the polymer/water interface) originated from the field-effect worked cooperatively to amplify the sensitivity for GlyP. The limit of detection of WG-OTFT (0.26 ppm) was lower than that of a fluorescence sensor chip (0.95 ppm) which is the conventional sensing method. In contrast to the previously reported insulated molecular wires to block interchain interactions, molecular aggregates under the field-effect has shown to be effective for amplification of sensitivity through “intra”- and “inter”-molecular wire effects. The opposite strategy in this study could pave the way for fully utilizing the sensing properties of polymer-based solid-state sensor devices.     

Carrier Protein Mediated Formation of the Dihydropyridazinone Ring in Actinopyridazinone Biosynthesis

Heterocycles with nitrogen-nitrogen (N−N) bonds are privileged building blocks of synthetic drugs. They are also found in natural products, although the biosynthetic logic behind them is poorly understood. Actinopyridazinones produced by Streptomyces sp. MSD090630SC-05 possess unique dihydropyridazinone rings that have been studied as core nuclei in several approved synthetic therapeutics. Herein, we performed gene knockouts and in vitro biochemical experiments to elucidate the major steps in actinopyridazinone biosynthesis, including the unprecedented carrier protein mediated machinery for dihydropyridazinone formation.     

Algorithms for image recovery calculation in extended single-shot phase-shifting digital holography

Optical Review - The single-shot phase-shifting method of image recovery using an inclined reference wave has the advantages of reducing the effects of vibration, being capable of operating in real...