Hyrtimomines,indole alkaloids from Okinawan marine sponges Hyrtios spp.

Six new indole alkaloids, hyrtimomines F–K (1–6), were isolated from Okinawan marine sponges Hyrtios spp. The structures of 1–6 were elucidated on the basis of spectroscopic analysis. Hyrtimomine F (1) is a structurally unique bisindole alkaloid possessing an α-keto-?-caprolactam ring, while hyrtimomine G (2) is a symmetrical bisindole alkaloid. Hyrtimomines H–K (3–6) are indole alkaloids possessing β-carboline skeleton with an imidazolium unit. Antimicrobial activities of hyrtimomines F–K (1–6) were evaluated.     

Effect of forewing and hindwing interactions on aerodynamic forces and power in hovering dragonfly flight

Dragonflies are four-winged insects that have the ability to control aerodynamic performance by modulating the phase lag (phi) between forewings and hindwings. We film the wing motion of a tethered dragonfly and compute the aerodynamic force and power as a function of the phase. We find that the out-of-phase motion as seen in steady hovering uses nearly minimal power to generate the required force to balance the weight, and the in-phase motion seen in takeoffs provides an additional force to accelerate. We explain the main hydrodynamic interaction that causes this phase dependence.     

The Effects of a Third Generation Combined Oral Contraceptive Pill on the Classical Singing Voice

The success of professional operatic singers depends upon the quality of their vocal mechanism. This is known to be sensitive to changes in the endocrine environment. Despite a widespread belief among singers that vocal quality changes according to the stage of the menstrual cycle, this has received little attention. In particular, the possibility that use of the contraceptive pill might stabilize vocal quality by "dampening" hormonal fluctuations has not previously been studied systematically. Here, we show that drospirenone containing oral contraceptive pill (Yasmin, Schering AG, West Sussex, UK) with antiandrogenic and antimineralocorticoid properties demonstrates a significant reduction in the irregularity of the pattern of vibration of the vocal folds during the performance of highly trained classical singers. This study constitutes the first double blind, randomized placebo controlled trial to assess the effects of the contraceptive pill on the patterns of vibration of the vocal folds during the performance of Western classical singing repertoire.     

Temperature Dependence for Fluorescence of β-NADH in Glycerol/Water Solution and in Trehalose/Sucrose Glass

Fluorescence imaging of cells and tissue can be used to evaluate β-NADH redox and location. At low temperature, β-NADH fluorescence intensity increases and therefore sensitivity of imaging increases. In this paper, the temperature dependence of fluorescence was evaluated for β-NADH in glycerol/water solution and in trehalose/sucrose glass. The average fluorescence lifetime for NADH in glycerol/water is 0.66 ns, compared with 5.3 ns in trehalose/ sucrose at 20°C. Emission spectra were recorded from 290 to 12 K. The fluorescence of β-NADH in glycerol/water increases ∼16 fold and the emission shifts about 35 nm to the blue as temperature decreases. Much smaller change is seen for fluorescence of β-NADH in sugar glass. Below 77 K, the β-NADH spectral features did not change significantly with temperature change, and so no increase in sensitivity is obtained by going to very low temperatures. It is suggested that the sensitivity of β-NADH fluorescence is related to water relaxation around the excited state molecule. Differences in water in various tissues may contribute to β-NADH fluorescence changes when cells are altered.     

One‐Step Multicomponent Self‐Assembly of a First‐Generation Sierpiński Triangle: From Fractal Design to Chemical Reality

A novel terpyridine‐based architecture that mimics a first‐generation Sierpiński triangle has been synthesized by multicomponent assembly and features tpy? Cd^II? tpy connectivity (tpy=terpyridine). The key terpyridine ligands were synthesized by the Suzuki cross‐coupling reaction. Mixing two different terpyridine‐based ligands and Cd^II in a precise stoichiometric ratio (1:1:3) produced the desired fractal architecture in near‐quantitative yield. Characterization was accomplished by NMR spectroscopy, mass spectrometry, and transmission electron microscopy.     

Surface characterization of synthetic and mineral carbonate fluoroapatites

As part of a larger project concerning the sorption capacities of carbonate fluoroapatites, the physical and surface properties of the synthetic carbonate fluoroapatite and mineral francolite retained for this work have been carefully examined. The average particle size of the powdered samples, determined by laser granulometry, is around 30 microm. Their specific surface areas, measured according to the N(2) BET method, are 8.8+/-0.1 and 13.9+/-0.1 m(2).g(-1), respectively, for the synthetic and the mineral compound. The solubility of both solids has been studied under undersaturation initial conditions. The synthetic compound has a solubility product of 10(-103+/-2), but the mineral francolite, which is highly substituted and poorly crystalline, is more soluble and dissolves incongruently. The amphoteric properties of the hydrous carbonate fluoroapatites surfaces have also been investigated through zeta-potential measurements and potentiometric titrations in KNO(3) medium at 25 degrees C. The experimental data have been interpreted using the computer program FITEQL 3.2, applying either the nonelectrostatic or the constant capacitance model. For both solids, the values of the surface acidity constants determined with the two models are very close, suggesting a weak contribution of the electrostatic interactions. Moreover, the more acidic surface of the synthetic compound compared to that of the mineral one is assigned to the differences in crystallinity and chemical composition between the two solids.     

Dual-mode recognition of oxalate by protonated azacryptate hosts; conformational response of the guest maximizes pi-stacking interactions

Exceptionally large complexation constants for oxalate encapsulated within azacryptand hosts are partly explained by pi-stacking interactions between C=O and aromatic rings.