Nuestra profesión bibliotecaria: una misión, un reto y una pasión

[ES] Partiendo de unas premisas sobre la que ha sido y es en la actualidad la profesión del bibliotecario, se analizan cuatro puntos sobre los que se asienta el nuevo papel de los profesionales de las bibliotecas en la actualidad, que son: definición de las funciones propias de la profesión; misión que debe cumplir un bibliotecario profesional; retos que se plantean en el momento actual; la profesión vivida como una pasión

Estudio del polimorfismo del gen inmunosupresor HLA-G, en amerindios

El complejo mayor de histocompatibilidad (MHC, del inglés Major Histocompatibility Complex), constituye un conjunto de genes, en su mayoría altamente polimórficos, cuyos productos se expresan en la superficie de gran variedad de células y que son responsables de la respuesta inmune “adaptativa”. Se considera que estos genes están presentes en todos los vertebrados. Estas moléculas son glicoproteínas de membrana, que actúan como presentadoras de antígeno a los linfocitos T. Se han definido clásicamente como antígenos de trasplante, ya que median las reacciones de rechazo que se producen contra los injertos de órganos. El sistema principal de histocompatibilidad del hombre se denomina sistema HLA (del inglés, Human Leukocyte Antigen). Se localiza físicamente en el brazo corto del cromosoma 6 humano, ocupando una región de aproximadamente 4 millones de pares de bases (4Mb). La función principal de las moléculas HLA es facilitar el despliegue de fragmentos moleculares únicos en la superficie de las células, en un orden que permite su identificación mediante efectores inmunes, como los Linfocitos T. las moléculas HLA de clase I y clase II son glicoproteínas de membrana responsables de los pasos de reconocimiento y unión, mientras que otros genes de esta región, contribuyen en el procesamiento y presentación antigénico de otra forma. Un gen polimórfico es aquel que tiene una alta frecuencia de variantes genéticos, y los genes HLA son los más polimórficos de la especie humana. Esto se debe a su principal papel en la respuesta inmune..

Pyroelectric Trapping and Arrangement of Nanoparticles in Lithium Niobate Opposite Domain Structures

The particular ferroelectric domain structure of periodic opposite domain lithium niobate (ODLN) crystals has been used for the first time for structured nanoparticle trapping. The surface charge density produced by a temperature change in this pyroelectric material is the origin of the trapping forces: dielectrophoretic on neutral particles and electrophoretic on charged ones. Metallic and dielectric particles are trapped and structured. The results show that ODLN structures are efficient substrates for pyroelectric trapping. The different trapping behaviors are presentedThis work has been supported by the Spanish Ministerio de Economía y Competitividad under grant ref.: MAT2014-57704-C3-1-

Real-time operation of photovoltaic optoelectronic tweezers: new strategies for massive nano-object manipulation and reconfigurable patterning

"This is the peer reviewed version of the following article: Particle and Particle Systems Characterization 36.91 (2019): 1900233 which has been published in final form at https://doi.org/10.1002/ppsc.201900233. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions. This article may not be enhanced, enriched or otherwise transformed into a derivative work, without express permission from Wiley or by statutory rights under applicable legislation. Copyright notices must not be removed, obscured or modified. The article must be linked to Wiley’s version of record on Wiley Online Library and any embedding, framing or otherwise making available the article or pages thereof by third parties from platforms, services and websites other than Wiley Online Library must be prohibited"Optical and optoelectronic techniques for micro- and nano-object manipulation are becoming essential tools in nano- and biotechnology. Among optoelectronic manipulation platforms, photovoltaic optoelectronic tweezers (PVOTs) are an emergent technique that are particularly successful at producing permanent nanoparticle microstructures. New strategies to enhance the capabilities of PVOT, based on real-time operation, are investigated. This optoelectronic platform uses z-cut LiNbO3:Fe substrates under excitation by a Gaussian light beam. Unexpected results show that during illumination, metallic particles previously deposited on the substrate are ejected from the light spot region. This behavior differs from the trapping phenomenon observed in previous work on PVOT operation, using a sequential method in which illumination is prior to particle manipulation. To discuss the results, a novel mechanism of charge exchange between particles and the ferroelectric substrate is proposed. Applications of this repulsion behavior are investigated. On the one hand, either particle repulsion or trapping in the illuminated region can be obtained by simply light switching on/off. On the other hand, by moving the light spot, different kinds of arbitrarily shaped tracks along the light path, either empty or filled with particles, are obtained. The results demonstrate new key capabilities of PVOT, such as pattern drawing, erasure, and reconfigurationFinancial support from Ministerio de Ciencia, Innovación y Universidades of Spain (MAT2014-57704-C3, MAT2017-83951-R) is gratefully acknowledge

Electrophoretic versus dielectrophoretic nanoparticle patterning using optoelectronic tweezers

Currently, there is increasing interest from many scientific disciplines in the development of systems that are able to sort and arrange many objects in parallel at the nano-and micrometric scale. Among others, photovoltaic tweezers (PVT) are an optoelectronic technique for trapping and patterning nano-and micro-objects in accordance with an arbitrary light profile. In this work, the differential features of electro-and dielectrophoretic (EP and DEP) nanoparticle (NP) patterning using PVT are deeply investigated. The study is carried out through theory and experiments. The developed theory extends the applicability of a previously reported model to be able to compute EP potentials and to obtain numerical values for the EP and DEP potential energies. Two-dimensional patterns of charged and neutral aluminum NPs are fabricated on top of Fe:LiNbO3 crystals, and different light distributions and other experimental parameters (crystal thickness and NP concentration) are compared. Patterns of charged and neutral NPs show remarkable differences in both particle density distribution and fidelity to the original light profile. The observed different features between EP and DEP trapping are satisfactorily explained by the theoretical analysis. The results provide routes for the optimization of the NP arrangements for both regimes.This work is supported by the Spanish Ministerio de Economía y Competitividad under Grant No. MAT201457704-C3. J.F.M.-M. is partially supported by a fellowship of the Universidad Politécnica de Madrid (Grant No. RR01/2016

Continuous culture methodology for the screening of microalgae for oil

A basic criterion in the selection of microalgae suitable as source of oil for biodiesel should be their actual capacity to produce lipids or, more properly, the fatty acid yield. Performance assessment of ten preselected microalgae under both batch and continuous culture points to the latter approach as the most adequate for evaluating fatty acid productivity. Differences were patent in continuous culture among strains that otherwise had analogous oil accumulation potential under batch culture. Some promising strains under batch culture (like Muriella aurantiaca and Monoraphidium braunii) exhibited, however, values for actual fatty acid productivity lower than 40 mg L-1d-1 in continuous regime. The analysis performed in photochemostat under continuous culture regime revealed the great potential of Chlorococcum olefaciens, Pseudokirchneriella subcapitata and Scenedesmus almeriensis as oil producing microalgae. Fatty acid productivity levels over 90 mg L-1d-1 were recorded for the latter strains under moderate nitrogen limitation, conditions which led to an enrichment in saturated and monounsaturated fatty acids, a more suitable profile as raw material for biodiesel. The continuous culture methodology employed represents a sound procedure for screening microalgae for biofuel production, providing a reliable evaluation of their fatty acid production capacity, under conditions close to those of outdoor production systemsEspaña MCINN Project CTQ2008-06741-CO2-02/PP

A protein with simultaneous capsid scaffolding and dsRNA-binding activities enhances the birnavirus capsid mechanical stability

Viral capsids are metastable structures that perform many essential processes; they also act as robust cages during the extracellular phase. Viruses can use multifunctional proteins to optimize resources (e.g., VP3 in avian infectious bursal disease virus, IBDV). The IBDV genome is organized as ribonucleoproteins (RNP) of dsRNA with VP3, which also acts as a scaffold during capsid assembly. We characterized mechanical properties of IBDV populations with different RNP content (ranging from none to four RNP). The IBDV population with the greatest RNP number (and best fitness) showed greatest capsid rigidity. When bound to dsRNA, VP3 reinforces virus stiffness. These contacts involve interactions with capsid structural subunits that differ from the initial interactions during capsid assembly. Our results suggest that RNP dimers are the basic stabilization units of the virion, provide better understanding of multifunctional proteins, and highlight the duality of RNP as capsidstabilizing and genetic information platformsThis work was supported by grants from the Spanish Ministry of Economy and Competitivity (FIS2011-29493 to PJP, BFU2011-29038 to JLC and BFU2014-55475R to JRC) and Comunidad Autónoma de Madrid (S2013/MIT-2850 to JLC and S2013/MIT-2807 to JRC

Micro-patterns of gold nanoparticles assembled by photovoltaic optoelectronic tweezers: application to plasmonic fluorescence enhancement

Noble metal nanostructures are well-known for their ability to increase the efficiency of different optical or physical phenomena due to their plasmonic behavior. This work presents a simple strategy to obtain Au plasmonic patterns by optically induced nanoparticle assembly and its application as fluorescence enhancement platforms. This strategy is based on the so-called photovoltaic optoelectronic tweezers (PVOT) being the first time they are used for fabricating Au periodic micro-patterns. Fringe patterns with a sub-structure of aggregates, assembled from individual spherical nanoparticles of 3.5 or 170 nm diameters, are successfully obtained. The spatial distribution of the aggregates is controlled with micrometric accuracy and the patterns can be arranged over large-scale active areas (tens of mm2). The outcome for the ultra-small (3.5 nm) particles is particularly relevant because this diameter is the smallest one manipulated by PVOT so far. Testing experiments of plasmonic fluorescence enhancement show that the 170-nm patterns present a much better plasmonic behavior. For the 170-nm platform they reveal a 10-fold enhancement factor in the fluorescence of Rhodamine-B dye molecules and a 3-fold one for tagged DNA biomolecules. Hence, the results suggest that these latter plasmonic platforms are good candidates for efficient bio-imaging and biosensing techniques, among other applications

Comparative theoretical analysis between parallel and perpendicular geometries for 2D particle patterning in photovoltaic ferroelectric substrates

This paper describes the dielectrophoretic potential created by the evanescent electric field acting on a particle near a photovoltaic crystal surface depending on the crystal cut. This electric field is obtained from the steady state solution of the Kukhtarev equations for the photovoltaic effect, where the diffusion term has been disregarded. First, the space charge field generated by a small, square, light spot where d < l (being d a side of the square and l the crystal thickness) is studied. The surface charge density generated in both geometries is calculated and compared as their relation determines the different properties of the dielectrophoretic potential for both cuts. The shape of the dielectrophoretic potential is obtained and compared for several distances to the sample. Afterwards other light patterns are studied by the superposition of square spots, and the resulting trapping profiles are analysed. Finally the surface charge densities and trapping profiles for different d/l relations are studied