Immobilization of proteins in silica gel: Biochemical and biophysical properties

The development of silica-based sol-gel techniques compatible with the retention of protein structure and function started more than 20 years ago, mainly for the design of biotechnological devices or biomedical applications. Silica gels are optically transparent, exhibit good mechanical stability, are manufactured with different geometries, and are easily separated from the reaction media. Biomolecules encapsulated in silica gel normally retain their structural and functional properties, are stabilized with respect to chemical and physical insults, and can sometimes exhibit enhanced activity in comparison to the soluble form. This review briefly describes the chemistry of protein encapsulation within the pores of a silica gel three-dimensional network, the mechanism of interaction between the protein and the gel matrix, and its effects on protein structure, function, stability and dynamics. The main applications in the field of biosensor design are described. Special emphasis is devoted to silica gel encapsulation as a tool to selectively stabilize subsets of protein conformations for biochemical and biophysical studies, an application where silica-based encapsulation demonstrated superior performance with respect to other immobilization techniques

Photolysis of pyruvic acid in ice: Possible relevance to CO and CO_2 ice core record anomalies

The abnormal spikes detected in some CO and CO_2 polar ice core records indicate persistent chemical activity in glacial ice. Since CO and CO_2 spikes are correlated, and their amplitudes scale with reported CO/CO_2 yields for the photolysis of dissolved natural organic matter, a common photochemical source is implicated. Given that sufficient actinic radiation is constantly generated throughout ice by cosmic muons (Colussi and Hoffmann, 2003), it remains to be shown that the photolyses of typical organic contaminants proceed by similar mechanisms in water and ice. Here we report that the photodecarboxylation of pyruvic acid (PA, an ubiquitous ice contaminant) indeed leads to the same products nearly as efficiently in both media. CO_2 is promptly released from frozen PA/H_2O films upon illumination and continues to evolve after photolysis. By analogy with our studies in water (Guzmán et al., 2006b), we infer that ^3PA* reacts with PA in ice producing CH_3C(O)C(O)O· and (CH_3C•(OH)C(O)OH) radicals. The barrierless decarboxylation, CH3C(O)C(O)O· → CH_3C(O)· + CO_2, accounts for prompt CO_2 emissions down to ∼140 K. Bimolecular radical reactions subsequently ensue in fluid molecular environments, both in water and ice, leading to metastable intermediates that decarboxylate immediately in water, but protractedly in ice. The overall quantum yield of CO_2 production in the λ ~313 nm photolysis of PA in ice at 250 K is ∼60% of that in water at 293 K. The in situ photolysis of natural organic matter is, therefore, a plausible explanation of CO and CO_2 ice core record anomalies

The effects of energetic proton bombardment on polymeric materials: Experimental studies and degradation models

This report describes 3 MeV proton bombardment experiments on several polymeric materials of interest to NASA carried out on the Tandem Van De Graff Accelerator at the California Institute of Technology's Kellogg Radiation Laboratory. Model aromatic and aliphatic polymers such as poly(1-vinyl naphthalene) and poly(methyl methacrylate), as well as polymers for near term space applications such as Kapton, Epoxy and Polysulfone, have been included in this study. Chemical and physical characterization of the damage products have been carried out in order to develop a model of the interaction of these polymers with the incident proton beam. The proton bombardment methodology developed at the Jet Propulsion Laboratory and reported here is part of an ongoing study on the effects of space radiation on polymeric materials. The report is intended to provide an overview of the mechanistic, as well as the technical and experimental, issues involved in such work rather than to serve as an exhaustive description of all the results

Supercritical fluid extraction: Recent advances and applications

17 páginas, 2 figuras, 5 tablas.Among the different extraction techniques used at analytical and preparative scale, supercritical fluid extraction (SFE) is one of the most used. This review covers the most recent developments of SFE in different fields, such as food science, natural products, by-product recovery, pharmaceutical and environmental sciences, during the period 2007–2009. The revision is focused on the most recent advances and applications in the different areas; among them, it is remarkable the strong impact of SFE to extract high value compounds from food and natural products but also its increasing importance in areas such as heavy metals recovery, enantiomeric resolution or drug delivery systems.M. H. would like to thank MEC for his Juan de la Cierva contract. This work was supported by an AGL2008-05108-C03-01 (Ministerio de Educacion y Ciencia) and CSD2007-00063 FUN-C-FOOD (Programa CONSOLIDER-INGENIO 2010) projects.Peer reviewe

Exploiting novel automated analytical methodologies for the monitoring of environmental organic pollutants, and its potential incorporation to environmental monitoring regulations

Se han desarrollado métodos analíticos basados en cromatografía y detección por espectrometría de masas para la detección de múltiples compuestos orgánicos a niveles traza en muestras de interés ambiental. Se han determinado compuestos volátiles en aire atmosférico de Mallorca y varias plantas de tratamiento de residuos y vertederos, y fármacos de consumo humano en muestras del medioambiente acuático de Mallorca, plantas de tratamiento de aguas y lixiviados de vertederos. Con estos datos se ha evaluado la necesidad de modificar los planes de vigilancia ambiental para asegurar la calidad del medioambiente de MallorcaWe have developed analytical methodologies based on chromatography and mass spectrometry for the detection of multiple different organic compounds in the trace levels in samples of environmental interest. Volatile organic compounds have been determined in the atmospheric air of Mallorca as well as some waste treatment plants and landfills. Pharmaceuticals for human consumption have been investigated in several samples of the aquatic environment of Mallorca as well as some wastewater treatment plants and landfill leachates. Based on these data it has been evaluated the necessity to modify the environmental monitoring regulations to save the quality of the Mallorca’s environment

The influence of solute diffusion and anisotropic elasticity on the deformation of iron: a study using planar discrete dislocation plasticity

Plastic deformation of crystalline metals is facilitated by crystallographic defects called dislocations. In certain alloys at certain temperatures and loading rates, the motion of these dislocations can become chaotic and unstable. This is a phenomenon related to dynamic strain ageing called the Portevin–Le Châtelier effect. The effect occurs when impurities, such as carbon and nitrogen, segregate to dislocations and obstruct their motion, leading to reduced ductility, hardening, and in the worst case, mechanical failure. In this thesis, I model plasticity with planar discrete dislocation plasticity. I extend planar discrete dislocation plasticity using anisotropic elasticity and introduce discrete diffusing solutes. This is used to understand the deformation of iron; and the onset and progression of the Portevin– Le Châtelier effect. Results from the model show that the nature of the diffusing solute field significantly affects the manifestation of the Portevin–Le Châtelier effect. As the solute concentration increases, the iron specimen’s proof stress, flow stress and solute strengthening increases; and the serrations recorded in a stress-strain curve (symptomatic of the Portevin–Le Châtelier effect) become smaller and occur at a slower frequency. Conversely, as the solute diffusivity increases, the serrations become larger and occur at a faster frequency. Furthermore, I show that anisotropic elasticity alters the mechanisms of plastic deformation of α-iron at elevated temperatures; specifically, that a type edge dislocations, which are energetically unfavourable at moderate temperatures, are nucleated in increasing numbers. This agrees with experimental observations found in the literature but cannot be predicted by isotropic elastic models. The increase in a edge dislocations is symptomatic of the precipitous decrease in the yield strength of iron. My work has important consequences for the application of steels in elevated temperature environments such as generation IV very high temperature nuclear fission reactors.Open Acces