Rails and anchors: guiding and trapping droplet microreactors in two dimensions

This paper presents a method to control the motion of nanolitre drops in a wide and thin microchannel, by etching fine patterns into the channel's top surface. Such control is possible for drops that are squeezed by the channel roof, by allowing them to reduce their surface energy as they enter into a local depression. The resulting gain in surface energy pulls a drop into the groove such that localized holes can be used as anchors for holding drops, while linear patterns can be used as rails to guide them along complex trajectories. An anchored drop can remain stationary indefinitely, as long as the driving flow rate is below a critical value which depends on the hole and drop sizes. By micro-fabricating holes into a grid pattern, drops can be arrayed and held in the observation field of a microscope against the mean carrier flow. Their contents can then be modulated by gas exchange with the flowing carrier oil. We demonstrate in particular how the pH or the oxygen levels within the drops can be controlled spatially and temporally, either by exposing rows of drops to two streams of oil at different gas concentrations or by periodically switching oil inputs to vary the gas concentration of drops as a function of time. Oxygen control is used to selectively deoxygenate droplets that encapsulate red blood cells from patients suffering from sickle cell disease, in order to study the polymerization of intracellular hemoglobin. Cycles of oxygenation and deoxygenation of anchored droplets induce depolymerization and polymerization of the hemoglobin, thus providing a method to simulate the cycling that takes place in physiological flows.     

Fourier-transform coherent anti-Stokes Raman scattering microscopy

We report a novel Fourier-transform-based implementation of coherent anti-Stokes Raman scattering (CARS) microscopy. The method employs a single femtosecond laser source and a Michelson interferometer to create two pulse replicas that are fed into a scanning multiphoton microscope. By varying the time delay between the pulses, we time-resolve the CARS signal, permitting easy removal of the nonresonant background while providing high resolution, spectrally resolved images of CARS modes over the laser bandwidth (approximately 1500 cm(-1)). We demonstrate the method by imaging polystyrene beads in solvent.     

Conformational Properties and Putative Bioactive Targets for Novel Thiosemicarbazone Derivatives

The structure assignment and conformational analysis of the thiosemicarbazones, DKI21 and DKI24, were performed through homonuclear and heteronuclear 2D Nuclear Magnetic Resonance (NMR) spectroscopy (2D-COSY, 2D-NOESY, 2D-ROESY, 2D-HSQC, and 2D-HMBC) and quantum mechanics (QM) calculations, using Functional Density Theory (DFT). In addition, utilizing a combination of 2D-NOESY and 2D-ROESY spectra an exo structure was established for both of the analogs. This experimental results were confirmed by theoretical mechanistic studies, as the lowest minima conformations derived through DFT calculations were compatible with the spatial correlations observed in the 2D-NOESY and 2D-ROESY spectra. Finally, molecular binding experiments were performed to detect the potential targets for DKI21 and DKI24, derived from SwissAdme. In silico molecular binding experiments showed favorable binding energy values for the most of the enzymes studied. The ADMET calculations, using the preADMET and pKCSm software, showed that the two molecules appear as possible drug leads.     

Synthesis and electron impact mass spectra of 3-substituted 2-acylaminoindazoles

3-Substituted-2-acylaminoindazoles 2 were prepared via oxidative cyclization of o-aminoaryl ketone acylhydrazones 1 with iodosobenzene diacetate. Their electron ionization mass spectra were recorded and in addition to the molecular ions show common fragmentation pathways corresponding to the [M-N₂]⁺, [M-NHCOX]⁺ and [M-COX]⁺ ions, with some influence on the skeletal fragmentation by different substituents.     

Electron impact mass spectra of some dioximes of o-diacyl benzenes

The electron impact mass spectra of the new synthesized dioximes of o-diacyl benzenes (2) are reported. In addition to the molecular ion, characteristic peaks appear at values corresponding to the [M ? OH] ⁺, [M ? NOH]⁺ and [M ? NHOH]⁺ ions. No initial dehydration of the molecular ion has been observed.     

Single lanthanide-doped oxide nanoparticles as donors in fluorescence resonance energy transfer experiments

We used lanthanide-ion doped oxide nanoparticles, Y(0.6)Eu(0.4)VO(4), as donors in fluorescent resonance energy transfer (FRET) experiments. The choice of these nanoparticles allows us to combine the advantages of the lanthanide-ion emission, in particular the long lifetime and the large Stokes shift between absorption and emission, with the detectability of the nanoparticles at the single-particle level. Using cyanine 5 (Cy5) organic molecules as acceptors, we demonstrated FRET down to the single-nanoparticle level. We showed that, due to the long donor lifetime, unambiguous and precise FRET measurements can be performed in solution even in the presence of large free acceptor concentrations. Highly efficient energy transfer was obtained for a large number of acceptor molecules per donor nanoparticle. We determined FRET efficiencies as a function of Cy5 concentration which are in good agreement with a multiple acceptor-multiple donor calculation. On the basis of the donor emission recovery due to acceptor photobleaching, we demonstrated energy transfer from single-nanoparticle donors in fluorescence microscopy experiments.     

Synthesis of 6,7-Diacylcoumarins via the Transformation of a Hydroxy into a Carbonyl Group

The synthesis of 6,7-diacylcoumarins is reported via the oxidation of 6-acetyl-7-hydroxycoumarin N-acylhydrazones with lead tetraacetate. The procedure involves transformation of hydroxy into an acyl group and formation of a new C–C bond.     

Isoflavonoid Profiling and Estrogen-Like Activity of Four Genista Species from the Greek Flora

As part of our ongoing research on phytoestrogens, we investigated the phytochemical profile and estrogen-like activities of eight extracts from the aerial parts of four Genista species of Greek flora using estrogen-responsive cell lines. Ethyl acetate and methanolic extracts of G. acanthoclada, G. depressa, G. hassertiana, and G. millii were obtained with accelerated solvent extraction and their phytochemical profiles were compared using ultra-high-performance liquid chromatography-high-resolution mass spectrometry (uHPLC-HRMS). Fourteen isoflavonoids, previously isolated from G. halacsyi, were used as reference standards for their identification in the extracts. Thirteen isoflavonoids were detected in both extracts of G. acanthoclada and G. hassertiana, while fewer and far fewer were detected in G. millii and G. depressa, respectively. The ethyl acetate extracts of G. hassertiana and G. acanthoclada displayed 2.45- and 1.79-fold higher, respectively, estrogen-like agonist activity in Ishikawa cells compared to MCF-7 cells at pharmacologically relevant concentrations. Both these extracts, but not that of G. depressa, contained mono- and di-O-β-d-glucosides of genistein as well as the aglycone, all three of which are known to display full estrogen-like activity at lower-than-micromolar concentrations. The possibility of using preparations rich in G. hassertiana and/or G. acanthoclada extracts as a potentially safer substitute for low-dose vaginal estrogen for menopausal symptoms is discussed.     

Luminescent oxide nanoparticles with enhanced optical properties

Yttrium vanadate particles doped with europium are studied for their applications as biomolecule labels. Two parts of our recent work are presented. The first concerns the thermal treatment of particles incorporated in a solid matrix. After annealing at 1000 °C and redispersion in water by dissolution of the matrix, the structural and optical properties are greatly improved without any modification of size; the obtained nanoparticles appear as perfect single crystals of 39 nm and have the same emission properties as the bulk material. Their quantum yield is worth 39% for 5% europium doping and the emission lifetime is 1 ms. The second aspect concerns the functionalization of the nanoparticles by the sol-gel condensation of aminopropyltriethoxysilane at the surface of particles. The chemical accessibility of amino groups grafted on the particles is measured by reaction with an organic fluorescent tag fluorescein isothiocyanate (FITC). These amine-coated nanoparticles were coupled to a peptidic toxin via a cross linker and allowed observation of the toxin motion bound to its membrane receptor.