186,600 research outputs found
Electroreduction of diphenyl disulfide on a self-assembled lipid monolayer on mercury
No full textIn the present work, a voltammetric study of permeability and redox behavior of diphenyl disulfide (Ph2S2) through a self-assembled monolayer of dioleoylphosphatidylcholine adsorbed on mercury is carried out; the results are compared with those obtained on a bare electrode; in this case, the reduction of Ph2S2 proceeds in a reversible way with the formation of a mercurial compound. The presence of the monolayer of phospholipid provokes an increase in the process irreversibility. Different mechanisms based on Ph2S2 adsorption either directly on a mercury drop or on phospholipids heads are proposed. The charge associated with the adsorbed Ph2S2 electroreduction was employed to calculate its solubility, and the method is compared with semiempirical expressions proposed in the literature for obtaining approximate values of solubility
The use of protonated Sargassum muticum as biosorbent for cadmium removal in a fixed-bed column
No full textThe protonated Sargassum muticum seaweed was studied as a possible biosorbent for cadmium removal in a fixed-bed column. The experiments were conducted in order to determine the effect of flow rate (0.42, 5, 10 and 20 mL min(-1)) and bed height (0.6 and 15.3 cm for the lowest flow rate or 7.4, 13 and 16.6 cm for the others) on breakthrough curves behaviour. The determined breakthrough and exhaustion times increased with the diminution in flow rate and with the increase in bed height. The maximum cadmium uptake capacity, obtained from the area below adsorbed cadmium concentration versus time curves, was found to remain practically constant with bed depth and flow rate. The bed depth service time (BDST) model was applied to analyse experimental data, determining the characteristic process parameters. The optimal lowest sorbent usage rate was evaluated at 2 min contact time and the minimum bed height values necessaries to prevent the effluent solution concentration from exceeding 0.02 mg L-1 at zero time were 5.3, 6.9 and 7.5 cm for flow rates of 5, 10 and 20 mL min(-1), respectively. Several empirical models proposed in the literature (Bohart-Adams, Yan, Belter and Chu models) were investigated in order to obtain the best fit of column data, describing in a simple manner the breakthrough curves. A correlation between model parameters and the variables implied in the process was attempted
The marine macroalga Cystoseira baccata as biosorbent for cadmium(II) and lead(II) removal: Kinetic and equilibrium studies
No full textThis work reports kinetic and equilibrium studies of cadmium(II) and lead(II) adsorption by the brown seaweed Cystoseira baccata. Kinetic experiments demonstrated rapid metal uptake. Kinetic data were satisfactorily described by a pseudo-second order chemical sorption process. Temperature change from 15 to 45 degrees C showed small variation on kinetic parameters. Langmuir-Freundlich equation was selected to describe the metal isotherms and the proton binding in acid-base titrations. The maximum metal uptake values were around 0.9 mmol g-1 (101 and 186 mg g-1 for cadmium(II) and lead(II), respectively) at pH 4.5 (raw biomass), while the number of weak acid groups were 2.2 mmol g-1 and their proton binding constant, K-H, 10(3.67) (protonated biomass). FTIR analysis confirmed the participation of carboxyl groups in metal uptake. The metal sorption was found to increase with the solution pH reaching a plateau above pH 4. Calcium and sodium nitrate salts in solution were found to affect considerably the metal biosorption
Batch desorption studies and multiple sorption-regeneration cycles in a fixed-bed column for Cd(II) elimination by protonated Sargassum muticum
No full textThe protonated alga Sargassum muticum was employed in batch desorption studies to find the most appropriate eluting agent for Cd(II)-laden biomass regeneration. Eleven types of eluting solutions at different concentrations were tested, finding elution efficiencies higher than 90\% for most of the desorbents studied. Total organic carbon and biomass weight loss measurements were made. The reusability of the protonated alga was also studied using a fixed-bed column. Eleven consecutive sorption-regeneration cycles at a flow rate of 10 mL min(-1) were carried out for the removal of 50 mg L-1 Cd(II) solution. A 0.1 M HNO3 solution was employed as desorbing agent. The column was operated during 605 h for sorption and 66 h for desorption, equivalent to a continuous use during 28 days, with no apparent loss of sorption performance. In these cycles, no diminution of the breakthrough time was found; although, a relative loss of sorption capacity, regarding the found in the first cycle, was observed. The slope of the breakthrough curves experiments a gradual increase reaching its maximum value for the last cycle tested (40\% greater than for the first one). The maximum Cd(II) concentration elution peak was achieved in 5 min or less, and the metal effluent concentration was always lower than 0.9 mg L-1 after 1 h of elution. The maximum concentration factor was determined to be between 55 and 109
Exploring the mitochondrial degradome by the TAILS proteomics approach in a cellular model of Parkinson’s disease
No full textAbstract
Among neurodegenerative diseases, Parkinson's disease (PD) is the second most frequent
worldwide. PD is primarily characterized by the specific loss of nigral dopaminergic neurons,
accompanied by the onset of cardinal motor symptoms [1]. Mitochondrial dysfunction appears to
have a major contribution in neuron cells death [2,3]. Dopaminergic neurons are more sensitive
to mitochondrial dysfunction than other neuron types since dopamine (DA) itself can undergo
spontaneous oxidation when not correctly stored in acidic vesicles, thus fostering mitochondrial
damage and oxidative stress [4]. A highly conserved system of mitochondrial proteases provides
a tool to ensure the maintenance of proper mitochondrial proteins activity [5]. Hence, the use of
a proteomics approach to study the complete repertoire of mitochondrial proteases (i.e.,
mitochondrial degradome) and their protein targets, in cellular models mimicking early
pathogenetic events in PD, represents a great chance for the discovery of new candidate disease
biomarkers.
The human neuroblastoma SH-SY5Y cell line is widely used as a cellular model to study PD
pathogenesis, since a marked increase in the cytoplasmic DA concentration can be reached upon
the addition of DA to the culture medium. Using this model, we have recently collected evidence
supporting the hypothesis of DA-induced activation of mitochondrial proteases [6-8].
A procedure termed TAILS (Terminal Amine Isotopic Labeling of Substrates) has been recently
designed for degradomics analysis [9]. In the present work, we re-adapted the TAILS protocol to
our specific aim, which is a comprehensive characterization of mitochondrial proteases and their
substrates in a cellular model of altered DA homeostasis in SH-SY5Y cells, which mimics the
early steps in PD pathogenesis. To this aim, SH-SY5Y cells were treated with DA (0.25 mM, 24
hours), mitochondria-enriched fractions were isolated and the TAILS bench protocol was
performed as described by Overall and coworkers [9].
As results, we identified so far 62 peptides whose presence and abundance is influenced by
dopamine. Among these, we found an interesting proteolytic peptide overexpressed in DA-treated
cells, belonging to the mitochondrial 39S ribosomal protein L49. Using the MEROPS database,
we have matched the cleavage site with that of a candidate protease, named neprilysin, that has
been already associated to neurodegeneration because of its ability to degrade the amyloid beta
peptide
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
The efficiency of the red alga Mastocarpus stellatus for remediation of cadmium pollution
No full textThis work reports the results of the study for cadmium binding by the dead red macroalga Mastocarpus stellatus. Kinetics sorption experiments demonstrated the high rate of metal biosorption: the system attained over 50% of the total biomass cadmium uptake within 2 min of contact and over 90% in the first 9 min. The kinetic data was successfully described by a pseudo-second order model with rate constants ranging from 1.06 to 10 gmmol-1 min-1, as a function of initial metal concentration and temperature. The equilibrium binding was accurately represented in terms of Langmuir and Langmuir-Freundlich models. The sorption isotherms at constant pH showed uptake values as 0.49 mmol g-1 (at pH 2.4), 0.56 mmol g-1 (at pH 4) and 0.59 mmol g-1 (at pH 6), while the affinity constant values were between 0.6 and 5 mmol-1 L (Langmuir fit). The acid-base properties of the alga were also studied, obtaining the total number of acid groups, 2.5 mmol g-1, and their apparent pK value, 1.56, using the Katchalsky model. Desorption studies were conducted employing different HNO3 concentrations and desorption times
Detection of silver nanoparticles in seawater at ppb levels using UV–visible spectrophotometry with long path cells
No full textSilver nanoparticles (AgNPs) are emerging contaminants that are difficult to detect in natural waters. UV–visible spectrophotometry is a simple technique that allows detection of AgNPs through analysis of their characteristic surface plasmon resonance band. The detection limit for nanoparticles using up to 10 cm path length cuvettes with UV–visible spectrophotometry is in the 0.1–10 ppm range. This detection limit is insufficiently low to observe AgNPs in natural environments. Here we show how the use of capillary cells with an optical path length up to 200 cm, forms an excellent technique for rapid detection and quantification of non-aggregated AgNPs at ppb concentrations in complex natural matrices such as seawater
REDU : revista de docencia universitaria
No full textResumen tomado de la publicaciónLos procesos de internacionalización y de búsqueda de la excelencia, que se vienen produciendo en las últimas décadas en la Universidad de Granada, han tenido distintos personajes clave entre los que destaca, por su vinculación a la gestión universitaria, el profesor Francisco González Lodeiro, actual Rector de la institución. Además de una amplia experiencia como docente e investigador ha sido Director del Departamento de Geodinámica, Delegado del Rector para la implantación de las enseñanzas propias, Vicerrector de Planificación Docente y Vicerrector de Investigación y Relaciones Internacionales. El relato de su trayectoria formativa, docente-investigadora y de gestión permite obtener una visión clara de ciertos elementos clave de los procesos antes mencionados, reconstruidos con los datos obtenidos a través de una entrevista semiestructurada realizada, durante su segundo mandato como Rector en junio de 2012.ES
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