Estructura de membranas biológicas mediante difracción de rayos X a ángulos bajos : aplicación al caso de la membrana púrpura del halobacterium halobium

Tesis Univ. Complutense de Madrid, 1981.Fac. de Ciencias FísicasTRUEProQuestpu

Optimización de la inmovilización de glucosa oxidasa en microgeles de poliacrilamida

The synthesis of polyacrylamide microgels using the concentrated emulsion pathway (W/O), without and with entrapped glucose oxidase from Aspergillus niger is proposed. The effect of initiator concentration in the maximum temperature of polymerization and the conversion rate of the monomer as a function of time were studied in the microparticles without enzyme. As a result of the polymerization, spherical micropart iculas were obtained in all the cases with a range of size between 2.5 ƒÝm and 6.2 ƒÝm of diameter In the microgels with enzyme the effect of the cross-linking content in the kinetic parameters was studied.. The use of the microgels with enzyme as the biological material of a amperometric biosensor allowed to evaluate the enzymatic activity of the glucose oxidase entrapped in the polymer. The catalytic activity of the entrapped enzyme and the biosensor response were affected by the cross-linking content of the microgel. The biosensor response was also affected by the quantity of microparticles immobilized in the surface of the electrode that acts as transducer of the biosensor.Se propone la sintesis de microgeles de poliacrilamida usando el metodo de polimerizacion en emulsion (W/O) concentrada, sin y con glucosa oxidasa de Aspergillus niger atrapada en su red polimerica. En las microparticulas sin enzima se estudio la influencia del agente iniciador en la temperatura maxima de polimerizacion y el grado de conversion del monomero en funcion del tiempo. Como resultado de la polimerizacion se obtuvieron en todos los casos microparticulas esfericas con un tamano comprendido entre 2,5ƒÝm y 6,2ƒÝm de diametro. En los microgeles con enzima se estudio la influencia del agente reticulante en diversos parametros cineticos. La utilizacion de las microparticulas con enzima como material biologico de un biosensor amperometrico permitio evaluar la actividad enzimatica de la glucosa oxidasa atrapada en su red polimerica. La actividad catalitica del enzima atrapado se vio afectada por el grado de reticulacion del microgel y como consecuencia la respuesta del biosensor sobre la que tambien influye la cantidad de microparticulas inmovilizadas en la superficie del electrodo que actua como transductor del biosensor

Mobbing en el sistema universitario gallego. El personal de administración y servicios

Las Administraciones Públicas se muestran, lamentablemente, como un campo especialmente abonado para el desarrollo de nocivas y gravísimas patologías, vicios y conflictos laborales, contradiciendo de este modo los más elementales principios que, por imperativo, obligación y, sobre todo, lógica, han de inspirar la actividad de la Administración. El acoso psicológico se ha convertido en una lacra laboral que azota con enorme virulencia a la Administración Pública. La Universidad Pública puede convertirse en un entorno laboral altamente tóxico si no se adoptan las medidas para corregir y prevenir este tipo de procesos, lo que obliga necesariamente a identificar el problema, sus causas y sus consecuencias.Regrettably the civil services are particularly prone to the onset of pernicious deficiencies within the working environment that contravene the most fundamental principles governing its procedures. Psychological harassment is a disgrace to the workforce and one that puts enormous pressure on the civil service. The public university will become a noxious environment within which to work unless measures are taken in both the prevention and correction of abuses, all of which necessitates a thorough identification of the problem in question together with its likely causes and consequences

Molecular dynamics of the α relaxation during crystallization of a glassy polymer: A real-time dielectric spectroscopy study

9 págs.; 12 figs.; 1 tab.The change of the α relaxation process occurring during isothermal crystallization of a glassy polymer, poly(aryl ether ketone ketone), has been followed in real time through measurement of the dielectric complex permittivity. The dielectric strength has been correlated with the degree of crystallinity derived from real time wide angle x-ray patterns using synchrotron radiation. The phenomenological Havriliak-Negami description has been used to analyze the changes of the dielectric strength, central relaxation time and shape parameters describing the relaxation, as crystallization proceeds. The evolution of the dielectric magnitudes with crystallization time has been interpreted in the light of the Schönhals-Schlosser model. According to this model, a restriction of the long scale motions of the polymeric chains as the material is filled in with crystals is observed. The derived dipole moment time correlation functions have been calculated for different crystallization times and fitted by the Kohlrausch-Williams-Watts function. The variation of the stretching parameters with crystallization time can be interpreted in terms of the coupling model assuming an increase of the intermolecular cooperativity of the α relaxation as the polymeric chains are constrained to move between crystalline regions. These results offer a contribution to the understanding of molecular dynamics of a glassy polymers during crystallization. © 1994 The American Physical Society.The authors are indebted to the CICYT (Grant No. MAT 94-0740E), Spain, for generous support of this investigation. J.M. thanks the Tempus Program (JEP 0644) for the support of his investigations.Peer Reviewe

Biosensor amperométrico para la medida de galactosa compuesto por microgeles de poliacrilamida

Galactosemia is one of the natural errors of the metabolism more frequent, its clinical representation in children not treated can be severe, sometimes mortal; its diagnostic is relatively simple and its treatment is very easy and effective. Hence, in last years new biosensors design for galactose determination based on galactose oxidase has been proposed. The aim of this work consists of the immobilization of galactose oxidase (GlOx) in polyacrylamide microparticles, using the concentrated emulsion method, and their use as biological material of a new amperometric biosensor for galactose determination. For preparing the galactose biosensors, microparticles with galactose oxidase were deposited on the surface of a platinum electrode and covered with a dialysis membrane. Microparticles were characterized by a Galai Cis-1 particle analyzer system, scanning electron microscopy, X-rays diffraction and differential scanning calorimetry. The presence of galactose oxidase decreases the transition temperature (Tg) of the polyacrylamide microgels. The influence of several experimental factors, such as crosslinking content, pH and temperature, on the biosensor response was investigated. The optimal performance of the biosensor takes place for a cross-linking of 7.0%, 40ºC and pH 7.0. The proposed immobilization system almost does not modify the enzyme activity, but seems to protect to the enzyme because an increase of the temperature range in which the enzyme is active is observed.La galactosemia es uno de los errores innatos del metabolismo más frecuentes. Su presentación clínica en niños no tratados puede ser severa, a veces mortal; su diagnóstico es relativamente simple y su tratamiento es muy sencillo y efectivo. Esto ha hecho que en los últimos años se hayan propuesto nuevos diseños de biosensores para la determinación de galactosa basados en galactosa oxidasa. El objetivo del trabajo consistió en la inmovilización de galactosa oxidasa (GlOx) en micropartículas de poliacrilamida (PAA), sintetizadas a partir del método de emulsión concentrada, y su utilización como material biológico de un nuevo biosensor amperométrico para la determinación de galactosa. Para preparar los biosensores de galactosa se depositaron las micropartículas con galactosa oxidasa sobre la superficie de un electrodo de platino y se cubrieron con una membrana de diálisis. Las micropartículas se caracterizaron mediante un analizador de partículas Galai Cis-1, microscopía electrónica de barrido, difracción de rayos X y calorimetría de barrido diferencial. La temperatura de transición vítrea (Tg) de los microgeles de poliacrilamida disminuyó al encapsular en su interior galactosa oxidasa. Se estudió la influencia de distintos factores, tales como grado de reticulación, pH y temperatura en la respuesta del biosensor. Las condiciones óptimas se corresponden a un grado de reticulación del 7%, 40º C y pH 7,0. El sistema de inmovilización propuesto apenas modifica la actividad enzimática, pero parece proteger a la enzima aumentando el intervalo de temperatura en el que es activa

Platelet-rich plasma may prevent titanium-mesh exposure in alveolar ridge augmentation with anorganic bovine bone

Objective: Bone augmentation with the titanium-mesh (Ti-mesh) technique is susceptible to a large rate of complications such as morbidity of bone graft donor site, and mesh exposure to the oral cavity. The purpose of this study was to evaluate the effectiveness of anorganic bovine bone (ABB) in alveolar bone augmentation with the Ti-mesh technique. In addition, we investigated the effect of platelet-rich plasma (PRP) in preventing mesh exposure by using it to cover the Ti-mesh. Patients and methods: Patients included in the clinical trial were randomly allocated by a blinded assistant into two groups. The 30 patients recruited for this study underwent 43 alveolar bone augmentation with the Ti-mesh technique using ABB as graft material in all of them. In 15 patients, the Ti-meshes were covered with PRP (PRP group) whereas in the other 15 the Ti-meshes were not (control group). After 6 months, patients were called for clinical, radiographic and histological evaluation, and implant placement surgery. A total of 97 implants were placed in the augmented bone and their evolution was followed up for a period of 24 months. Results: Significant differences were found between the two study groups in terms of complications and bone formation. In the control group, 28,5% of the cases suffered from mesh exposure, while in the PRP group, no exposures were registered. Radiographic analysis revealed that bone augmentation was higher in the PRP group than in the control group. Overall, 97,3% of implants placed in the control group and 100% of those placed in the PRP group were successful during the monitoring period. We suggest that the positive effect of PRP on the Ti-mesh technique is due to its capacity to improve soft tissue healing, thereby protecting the mesh and graft material secured beneath the gingival tissues. Conclusions: Alveolar bone augmentation using ABB alone in the Ti-Mesh technique is sufficient for implant rehabilitation. Besides, covering the Ti-meshes with PRP was a determining factor in avoiding mesh exposure. Ti-Mesh exposure provoked significant bone loss, but in most cases it did not affect the subsequent placement implants

Oligonucleotide Sensor Based on Selective Capture of Upconversion Nanoparticles Triggered by Target-Induced DNA Interstrand Ligand Reaction

We present a sensor that exploits the phenomenon of upconversion luminescence to detect the presence of specific sequences of small oligonucleotides such as miRNAs among others. The sensor is based on NaYF4:Yb,Er@SiO2 nanoparticles functionalized with ssDNA that contain azide groups on the 3' ends. In the presence of a target sequence, interstrand ligation is possible via the click-reaction between one azide of the upconversion probe and a DBCO-ssDNA-biotin probe present in the solution. As a result of this specific and selective process, biotin is covalently attached to the surface of the upconversion nanoparticles. The presence of biotin on the surface of the nanoparticles allows their selective capture on a streptavidin-coated support, giving a luminescent signal proportional to the amount of target strands present in the test samples. With the aim of studying the analytical properties of the sensor, total RNA samples were extracted from healthy mosquitoes and were spiked-in with a specific target sequence at different concentrations. The result of these experiments revealed that the sensor was able to detect 10-17 moles per well (100 fM) of the target sequence in mixtures containing 100 ng of total RNA per well. A similar limit of detection was found for spiked human serum samples, demonstrating the suitability of the sensor for detecting specific sequences of small oligonucleotides under real conditions. In contrast, in the presence of noncomplementary sequences or sequences having mismatches, the luminescent signal was negligible or conspicuously reduced.The authors are grateful for the financial support from the Bill & Melinda Gates Foundation, with Grant OPP1128411, Asociación Española Contra el Cáncer, Santander-Universidad Complutense project PR26/16-12B-3, and from the Spanish MINECO for the projects MAT2014-55065-R, SAF2014-56763-R, and FIS2013-41709-P.S

Contribution of resonance energy transfer to the luminescence quenching of upconversion nanoparticles with graphene oxide

Upconversion nanoparticles (UCNP) are increasingly used due to their advantages over conventional fluorophores, and their use as resonance energy transfer (RET) donors has permitted their application as biosensors when they are combined with appropriate RET acceptors such as graphene oxide (GO). However, there is a lack of knowledge about the design and influence that GO composition produces over the quenching of these nanoparticles that in turn will define their performance as sensors. In this work, we have analysed the total quenching efficiency, as well as the actual values corresponding to the RET process between UCNPs and GO sheets with three different chemical compositions. Our findings indicate that excitation and emission absorption by GO sheets are the major contributor to the observed luminescence quenching in these systems. This challenges the general assumption that UCNPs luminescence deactivation by GO is caused by RET. Furthermore, RET efficiency has been theoretically calculated by means of a semiclassical model considering the different nonradiative energy transfer rates from each Er3+ ion to the GO thin film. These theoretical results highlight the relevance of the relative positions of the Er3+ ions inside the UCNP with respect to the GO sheet in order to explain the RET-induced efficiency measurements

Silver nanoparticle based antibacterial methacrylate hydrogels potential for bone graft applications

Infections are frequent and very undesired occurrences after orthopedic procedures; furthermore, the growing concern caused by the rise in antibiotic resistance is progressively dwindling the efficacy of such drugs. Artificial bone graft materials could solve some of the problems associated with the gold standard use of natural bone graft such as limited bone material, pain at the donor site and rejections if donor tissue is used. We have previously described new acrylate base nanocomposite hydrogels as bone graft materials. In the present paper, we describe the integration of silver nanoparticles in the polymeric mineralized biomaterial to provide non-antibiotic antibacterial activity against Staphylococcus epidermidis and Methicillin-resistant Staphylococcus aureus. Two different crosslinking degrees were tested and the silver nanoparticles were integrated into the composite matrix by means of three different methods: entrapment in the polymeric hydrogel before the mineralization; diffusion during the process of calcium phosphate crystallization and adsorption post-mineralization. The latter being generally the most effective method of encapsulation; however, the adsorption of silver nanoparticles inside the pores of the biomaterial led to a decreasing antibacterial activity for adsorption time longer than 2 days

Obtaining new composite biomaterials by means of mineralization of methacrylate hydrogels using the reaction-diffusion method

The present paper describes the synthesis and characterization of a new polymeric biomaterial mineralized with calcium phosphate using the reaction–diffusion method. The scaffold of this biomaterial was a hydrogel constituted by biocompatible polyethylene glycol methyl ether methacrylate (PEGMEM) and 2-(dimethylamino)ethyl methacrylate (DMAEM), which were cross-linked with N-N’-methylenebisacrylamide (BIS). The cross-linking content of the hydrogels was varied from 0.25% to 15% (w/w). The gels were used as matrix where two reactants (Na2HPO4 and CaCl2) diffused from both ends of the gel and upon encountering produced calcium phosphate crystals that precipitated within the polymer matrix forming bands. The shape of the crystals was tuned by modifying the matrix porosity in such a way that when the polymer matrix was slightly reticulated the diffusion reaction produced round calcium phosphate microcrystals, whilst when the polymer matrix was highly reticulated the reaction yielded flat calcium phosphate crystals. Selected area electron diffraction performed on the nanocrystals that constitute the microcrystals showed that they were formed by Brushite (CaHPO4.2H2O). This new composite material could be useful in medical and dentistry applications such as bone regeneration, bone repair or tissue engineering