Acid-base properties of carbazole in the ground and lowest excited singlet states

The electronic absorption and fluorescence emission spectra of carbazole have been obtained in aqueous solutions of a wide range of acidity Cfrom 18M H2 SO4 to 14M KOHD. Ground and lowest excited singlet states pKa values of protonation and deprotonation equilibria of carbazole have been evaluated using the Excess Acidity Method

The Minorca peripheral depression and contourite drift: evidences for the activity of bottom currents on the northern balearic slope

A peripheral depression with a sediment drift on its N flank develop N and E of Minorca Island. Both are interpreted to result from the activity of bottom currents circulating parallel to the base of the island slope since the Pliocene. Evidences of the contouriric activity are: the presence of a depression with an erosive character, a sedimentary ridge with the typical characteristics of contourite drifts, and large sediment waves. The depression has a maximum width of 5 km, and a depth of 150-200 m, whereas the contourite drift reaches up to 150 km in length, is 25 km wide, and 100 m high. The sediment waves developed on the inner flank of the contourite drift reach up to 5 km in length and 40 m in height. The genesis of all these structures is related to the circulation of the Mediterranean Deep Water ( MDW) in the area. The steep island slope, devoided of sediment and deeply gullied, is considered as the potential source area for the sediments reworked by the currents. Further seaward, the contourite deposits are in lateral continuity with the deposits of the North-Balearic Basin and the Valencia Fa

Interaction between Poly(9,9-bis(6′-N,N,N-trimethylammonium)hexyl)fluorene phenylene) Bromide and DNA as Seen by Spectroscopy, Viscosity, and Conductivity: Effect of Molecular Weights and DNA Secondary Structure

The interaction between three poly(9,9-bis(6-N,N,N-trimethylammonium)hexyl)fluorene phenylene) bromide (HTMA-PFP) samples of different molecular weights (Mn = 14.5, 30.1 and 61.3 kg/mol) and both dsDNA and ssDNA secondary structures has been studied using UV−visible absorption and fluorescence spectroscopies (including steady-state, time-resolved, and anisotropy measurements for the latter), viscosity, and electrical conductivity in 4% (v/v) DMSO−water mixtures. At low nucleic acid concentrations, formation of a 1:1 complex in terms of HTMA-PFP repeat units and DNA bases occurs. This interaction results in quenching of polymer emission. For higher molar ratios of DNA to HTMA-PFP, corresponding to charge neutralization, a second process is observed that is attributed to aggregate formation. From the changes in the absorption spectra, the polymer aggregation constant and the aggregate absorption spectra were calculated by applying an iterative method. Polymer aggregation dramatically quenches HTMA-PFP fluorescence in the region of the electroneutrality point. Under these conditions, the ratio of the emission intensity at 412 nm (maximum) to that at 434 nm (I412/I434) reaches a minimum, the electrical conductivity decreases, and the viscosity of the solution remains constant, showing that the DNA concentration can be determined through various HTMA-PFP physicochemical properties. With respect to the photophysical parameters (emission quantum yield, shape and shift of emission spectra), no significant differences were observed between dsDNA and ssDNA or with conjugated polymer or DNA molecular weight. The two short-lived components in the fluorescence decays are attributed to the presence of aggregates. Aggregates are also suggested to be responsible for the decrease in the fluorescence anisotropy through interchain exciton migration

Fast determination of harmala alkaloids in edible algae by capillary electrophoresis mass spectrometry

The use of algae as a foodstuff is rapidly expanding worldwide from the East Asian countries, where they are also used for medical care. Harmala alkaloids (HAlk) are a family of bioactive compounds found in the extracts of some plants, including wakame (Undaria pinnatifida), an edible marine invasive algae. HAlks are based on a characteristic β-carboline structure with at least one amino ionizable group. In this work, we report the successful separation of a mixture of six HAlks (harmine, harmaline, harmol, harmalol, harmane, and norharmane) by capillary electrophoresis ion-trap mass spectrometry (CE-IT-MS) in less than 8 min. Optimum separation in fused-silica capillaries and detection sensitivity in positive-ion mode were achieved using a background electrolyte (BGE) with 25 mmol L−1 ammonium acetate (pH 7.8) and 10 % (v/v) methanol, and a sheath liquid with 60:40 (v/v) isopropanol–water and 0.05 % (v/v) formic acid. The separation method was validated in terms of linearity, limits of detection and quantification, repeatability, and reproducibility. Later, a sample pretreatment was carefully optimized to determine HAlks in commercial wakame samples with excellent recovery and repeatability. For the complex wakame extracts, the MS–MS fragmentation patterns of the different HAlks were useful to ensure a reliable identification. The complete procedure was validated using the standard-addition calibration method, determining matrix effects on the studied compounds. Harmalol, harmine, and harmaline were naturally present in the samples and were quantified at very low concentrations, ranging from 7 to 24 μg kg−1 dry algae.Fil: Tascon, Marcos. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Laboratorio de Investigación y Desarrollo de Métodos Analíticos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Benavente, Fernando. Universidad de Barcelona; EspañaFil: Sanz Nebot, Victoria M.. Universidad de Barcelona; EspañaFil: Gagliardi, Leonardo Gabriel. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Laboratorio de Investigación y Desarrollo de Métodos Analíticos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico La Plata. Centro de Investigación y Desarrollo en Tecnología de Pinturas (i); Argentina. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas; Argentin