Immobilization of Proteins in Poly-Styrene-Divinylbenzene Matrices: Functional Properties and Applications

Supports based on poly-styrene-divinylbenzene (PSD) are commercially available since a long time ago. However, they are not commonly used as enzyme immobilization matrices. The main reason for this lies in the negative effect of the very hydrophobic surface on enzyme stability that produces the instantaneous enzyme inactivation in many instances. However, they have recently regained some impact in enzyme immobilization. They are easy to modify, and have been prepared with different modifiers. We will pay special attention to the coating of these supports with ionic liquids, which permits to have the ionic liquid phase anchored to the solid and modulate the enzyme properties without risk of losing these expensive and potentially toxic compounds. Thus, this review will present the covalent or physical immobilization of enzymes on PSD supports, submitted to different modifications. Moreover, lipases immobilized via interfacial activation on some naked PSD supports have shown some unexpected improvement in their catalytic properties, with uses in reactions like hydrolysis, esterification or transesterification.We gratefully recognize the support from the Spanish Government, CTQ2013-41507-R and CNPq (Brazil). The predoctoral fellowships for Ms. García-Galán (Spanish Government), Mr K. Hernandez (I3P-CSIC) and Mr dos Santos (CNPq, Brazil) are also recognized. ). Á. Berenguer-Murcia thanks the Spanish Ministerio de Ciencia e Innovacion for a Ramon y Cajal fellowship (RyC-2009-03813)

Small variations in reaction conditions tune carbon dot fluorescence

The development of robust and reproducible synthetic strategies for the production of carbon dots with improved fluorescence quantum yields and distinct emission profiles is of great relevance given the vast range of applications of CDs. The fundamental understanding at a molecular level of their formation mechanism, chemical structure and how these parameters are correlated to their photoluminescence (PL) properties is thus essential. In this study, we describe the synthesis and structural characterization of a range of CDs with distinct physico-chemical properties. The materials were prepared under three minutes of microwave irradiation using the same common starting materials (GlcNH2·HCl 1 and EDA 2) but modifying the stoichiometry of the reagents. We show that small changes in reaction conditions leads to the tailoring of the fluorescent behaviour of the CDs from apparent blue to green emission. Structural analysis of the different CD samples suggested different reaction pathways during the CD formation and surface passivation, with the latter step being key to the observed differences. Moreover, we demonstrate that the different materials also respond reversibly to changes in pH, which we can attribute to different behaviour towards protonation/deprotonation events of distinct emission domains present within each nanomaterial. Our results highlight the importance of understanding the reaction pathways that lead to the formation of this carbon-based nanomaterials and how this can be exploited to develop tailored materials towards specific applications

Measuring the Refractive Index and Sub-Nanometre Surface Functionalisation of Nanoparticles in Suspension

Direct measurements to determine the degree of surface coverage of nanoparticles by functional moieties are rare, with current strategies requiring a high level of expertise and expensive equipment. Here, a practical method to determine the ratio of the volume of the functionalisation layer to the particle volume based on measuring the refractive index of nanoparticles in suspension is proposed. As a proof of concept, this technique is applied to poly(methyl methacrylate) (PMMA) nanoparticles and semicrystalline carbon dots functionalised with different surface moieties, yielding refractive indices that are commensurate to those from previous literature and Mie theory. In doing so, it is demonstrated that this technique is able to optically detect differences in surface functionalisation or composition of nanometre-sized particles. This non-destructive and rapid method is well-suited for in situ industrial particle characterisation and biological applications

A Stochastic Frontier Model to Determine Technical Efficiency of the Purse Seine Fishery in the Gulf of Cadiz (Spain)

In this paper we analyse different econometric procedures of technical efficiency to estimate fishing capacity. These procedures are then applied to the purse seine fishery located in the Gulf of Cádiz. The target species of this fishery has changed quite a lot over the past few years. It used to be mackerel (Scomber spp.). Afterwards, it was anchovy (Engraulis encrasicholus) and, recently, sardine (Sardina pilchardus). The regulation of anchovy and sardine fisheries by European Union is only based on Total Allowable Catch for vessels which are longer than 10 metres. This management measure could be unsuitable in this fishery for two reasons. Firstly, most of the vessels measure less than 10 metres and, secondly, there is a small interrelation between vessel efficiency and length.Keywords: purse seine fishing, Stochastic frontiers, Theoretical and Empirical Bio-Economic Modelling, panel data, Fisheries Economics, Fishing capacity, Gulf of Cadiz, management policie

Epigenetic Silencing of Host Cell Defense Genes Enhances Intracellular Survival of the Rickettsial Pathogen Anaplasma phagocytophilum

Intracellular bacteria have evolved mechanisms that promote survival within hostile host environments, often resulting in functional dysregulation and disease. Using the Anaplasma phagocytophilum–infected granulocyte model, we establish a link between host chromatin modifications, defense gene transcription and intracellular bacterial infection. Infection of THP-1 cells with A. phagocytophilum led to silencing of host defense gene expression. Histone deacetylase 1 (HDAC1) expression, activity and binding to the defense gene promoters significantly increased during infection, which resulted in decreased histone H3 acetylation in infected cells. HDAC1 overexpression enhanced infection, whereas pharmacologic and siRNA HDAC1 inhibition significantly decreased bacterial load. HDAC2 does not seem to be involved, since HDAC2 silencing by siRNA had no effect on A. phagocytophilum intracellular propagation. These data indicate that HDAC up-regulation and epigenetic silencing of host cell defense genes is required for A. phagocytophilum infection. Bacterial epigenetic regulation of host cell gene transcription could be a general mechanism that enhances intracellular pathogen survival while altering cell function and promoting disease

Identificación de flujos entre acuíferos a nivel regional en base a datos hidroquímicos (Alt Empordà, NE España)

A escala regional, los flujos de agua subterránea entre formaciones hidrogeológicas condicionan su ba lance hídrico y, con él, su régimen de explotación. En este estudio se caracteriza la dinámica hidrogeológica a nivel regional de la depresión del Alt Empordà (Girona, NE España) en base a datos hidroquímicos, con el objetivo de identificar flujos de agua subterránea entre las formaciones que constituyen la zona de recarga (relieves circundantes) y la depresión. En este sistema, el ión sulfato resulta un trazador adecuado para identificar los procesos hidroquímicos y de mezcla que acontecen en este zona. Los datos presentados sugieren que la presencia de sulfato, y por consiguiente la recarga, se debe a aportaciones de flujos profundos, en algunos casos desde las unidades geológicas inferiores, ajenos a la recarga local por precipitación desde la superficie.At a regional scale, groundwater flow between aquifer systems controls their water budget and, therefore, its exploitation regime. This study characterizes the hydrogeology at a regional level of the Alt Empordà Basin (Girona, NE Spain). Our goal consists in recognizing recharge flowpaths, based on hydrochemical data, between the aquifer systems located in the ranges (recharge) areas and these within the basin. Sulfate stands as an appropriate tracer to identify hydrochemical as well as mixing processes and, therefore, recharge relationships. Field data suggest that sulfate occurrence is related to deep groundwater fluxes unrelated to the local rainfall recharge.Universidad Nacional de La Plat

Surface brightness-colour relations of dwarf stars from detached eclipsing binaries: I. Calibrating sample

Aims. Surface brightness - colour relations (SBCRs) are very useful tools for predicting the angular diameters of stars. They offer the possibility to calculate very precise spectrophotometric distances by the eclipsing binary method or the Baade-Wesselink method. Double-lined Detached Eclipsing Binary stars (SB2 DEBs) with precisely known trigonometric parallaxes allow for a calibration of SBCRs with unprecedented precision. In order to improve such calibrations, it is important to enlarge the calibration sample of suitable eclipsing binaries with very precisely determined physical parameters. Methods. We carefully chose a sample of ten SB2 DEBs in the solar neighbourhood which contain inactive main-sequence components. The components have spectral types from early A to early K. All systems have high-precision parallaxes from the Gaia mission. We analysed high precision ground- and space-based photometry simultaneously with the radial velocity curves derived from HARPS spectra. We used spectral disentangling to obtain the individual spectra of the components and used these to derive precise atmospheric parameters and chemical abundances. For almost all components, we derived precise surface temperatures and metallicities. Results. We derived absolute dimensions for 20 stars with an average precision of 0.2% and 0.5% for masses and radii, respectively. Three systems show slow apsidal motion. One system, HD 32129, is most likely a triple system with a much fainter K6V companion. Also three systems contain metallic-line components and show strong enhancements of barium and ittrium. Conclusions. The components of all systems compare well to the SBCR derived before from the detached eclipsing binary stars. With a possible exception of HD 32129, they can be used to calibrate SBCRs with a precision better than 1% with available Gaia DR3 parallaxes

CAST constraints on the axion-electron coupling

In non-hadronic axion models, which have a tree-level axion-electron interaction, the Sun produces a strong axion flux by bremsstrahlung, Compton scattering, and axio-recombination, the "BCA processes." Based on a new calculation of this flux, including for the first time axio-recombination, we derive limits on the axion-electron Yukawa coupling g_ae and axion-photon interaction strength g_ag using the CAST phase-I data (vacuum phase). For m_a < 10 meV/c2 we find g_ag x g_ae< 8.1 x 10^-23 GeV^-1 at 95% CL. We stress that a next-generation axion helioscope such as the proposed IAXO could push this sensitivity into a range beyond stellar energy-loss limits and test the hypothesis that white-dwarf cooling is dominated by axion emission

CAST solar axion search with 3^He buffer gas: Closing the hot dark matter gap

The CERN Axion Solar Telescope (CAST) has finished its search for solar axions with 3^He buffer gas, covering the search range 0.64 eV < m_a <1.17 eV. This closes the gap to the cosmological hot dark matter limit and actually overlaps with it. From the absence of excess X-rays when the magnet was pointing to the Sun we set a typical upper limit on the axion-photon coupling of g_ag < 3.3 x 10^{-10} GeV^{-1} at 95% CL, with the exact value depending on the pressure setting. Future direct solar axion searches will focus on increasing the sensitivity to smaller values of g_a, for example by the currently discussed next generation helioscope IAXO.Comment: 5 pages, 2 figures. Last version uploade