Design optimization through thermomechanical finite-element analysis of a hybrid piston-clamped anvil cell for nuclear magnetic resonance experiments.

The investigation of materials under extreme pressure conditions requires high-performance cells whose design invariably involves trade-offs between the maximum achievable pressure, the allowed sample volume, and the possibility of real-time pressure monitoring. With a newly conceived hybrid piston-clamped anvil cell, we offer a relatively simple and versatile system, suitable for nuclear magnetic resonance experiments up to 4.4 GPa. Finite-element models, taking into account mechanical and thermal conditions, were used to optimize and validate the design prior to the realization of the device. Cell body and gaskets were made of beryllium-copper alloy and the pistons and pusher were made of tungsten carbide, while the anvils consist of zirconium dioxide. The low-temperature pressure cell performance was tested by monitoring in situ the pressure-dependent 63Cu nuclear-quadrupole-resonance signal of Cu2O.

Is it possible to study the kinetic parameters of interaction between PNA and parallel and antiparallel DNA by stopped-flow fluorescence?

Peptide nucleic acids (PNAs) are among the most interesting and versatile artificial structural mimics of nucleic acids and exhibit peculiar and important properties (i.e. high chemical stability, and a high resistance to cellular enzymes and nucleases). Despite their unnatural structure, they are able to recognize and bind DNA and RNA in a very high, specific and selective manner. One of the most popular, easy and reliable method to measure the stability of PNA-DNA hybrid systems is the melting temperature but the thermodynamic data are obtained using a big quantity of materials failing to provide information on the kinetics of the interaction. In the present work, the PNA decamer 6, with the TCACTAGATG sequence of nucleobases, and the corresponding fluorescent PNA-FITU (fluorescein isothiourea) decamer 8 were synthesized with standard manual Boc-based chemistry. The interaction of the PNA-FITU with parallel and antiparallel DNA has been studied by stopped-flow fluorescence, which is proposed as an alternative technique to obtain the kinetic parameters of the binding. The great advantage of using the stopped-flow technique is the possibility of studying the kinetics of the PNA-DNA duplex formation in a physiological environment. In particular, fluorescence stopped-flow technique has been exploited to compare the affinity of two PNA-DNA duplexes since it can discriminate between parallel and antiparallel DNA binding.

A multi-technique comparison of the electronic properties of pristine and nitrogen-doped polycrystalline SnO2.

Nitrogen doped tin(iv) oxide (SnO2) materials in the form of nanometric powders have been prepared by precipitation with ammonia. Their properties have been compared with those of undoped materials obtained in a similar way using various physical techniques such as photoelectron spectroscopies (XPS and UPS), UV-Vis-NIR spectroscopy and electron paramagnetic resonance (EPR). Nitrogen doping leads to the formation of various nitrogen containing species, the more relevant of which is a nitride-type ionic species, based on the substitution of a lattice oxygen atom with a nitrogen atom. This species exists in two forms, paramagnetic (hole centre, formally N(2-)) and diamagnetic (N(3-)). The mutual ratio of the two species varies according to the oxidation state of the material. The doped solid, like most of the semiconducting oxides, tends to lose oxygen forming oxygen vacancies upon annealing under vacuum and leaving an excess of electrons in the solid. The stoichiometry of the solid can thus be markedly changed depending on the external conditions. Excess electrons are present both as itinerant electrons in the conduction band and as Sn(ii) states lying close to the valence band maximum. The presence of nitride-type centres, which are low energy states located below the top of the valence band, decreases the energy cost for the formation of oxygen vacancies by O2 release from the lattice. This particular feature of the doped system represents a severe limit to the preparation of a p-type SnO2via nitrogen doping.

The role of IgE recognition in allergic reactions to amoxicillin and clavulanic acid.

Betalactam (BL) antibiotics are the drugs most frequently involved in IgE-mediated reactions. The culprit BL varies according to consumption patterns, with amoxicillin (AX) more prevalent in Southern Europe and penicillin V in Scandinavian countries. Nowadays, the combination of AX and clavulanic acid (CLV) is the most highly consumed BL containing medicine worldwide. Both BLs, AX and CLV, can independently be involved in reactions, which poses a diagnostic challenge. In patients with immediate allergic reactions to AX, two patterns of responses have been described, those responding to benzylpenicillin (cross-reactors) and those selective to AX. In addition, selective reactions to CLV account for around 30% of allergic reactions to the combination AX-CLV. These patterns of IgE recognition could be related to differences in the haptenation process, in the immunological response, or in the BL involved in the first sensitization. In this regard, patients with selective responses to CLV are generally younger than those allergic to AX or benzylpenicillin. So far, no evidence of cross-reactivity between CLV and other BLs has been reported. This shows the importance of an accurate diagnosis of CLV allergy, as patients with selective reactions to CLV could take other BLs including AX. Diagnosis can be performed in vivo and in vitro, although no immunoassay currently exists. Research regarding the CLV antigenic determinants and protein conjugates is essential to improve diagnosis. BLs need to covalently bind to a carrier protein to be immunogenic. The antigenic determinant of AX is the amoxicilloyl amide, but CLV leads to unstable structures, many of which are unknown. Moreover, the nature of the BL-protein conjugates plays an important role in IgE recognition. This review aims to summarize current knowledge on the immunochemistry, diagnostic approaches as well as chemical and proteomic studies for both AX and CLV.

Hypersensitivity reactions to ß-lactams: relevance of hapten-protein conjugates.

ß-Lactams (BL) are the drugs most frequently involved in allergic reactions. They are classified according to their chemical structure as penicillins, cephalosporins, monobactams, carbapenems, and clavams. All BL antibiotics have a BL ring that is fused to a 5-member or 6-member ring (except in monobactams) and has 1, 2 or 3 side chains (except in clavams). Differences in chemical structure mean that a wide range of BLs are recognized by the immune system, and patients may experience clinical reactions to one BL while tolerating others. Diagnosis is based on skin and in vitro testing, although both display low sensitivity, possibly because they are based on drugs or drug conjugates that are not optimally recognized by the immune system. BLs are haptens that need to bind to proteins covalently to elicit an immune response. These drugs have a high capacity to form covalent adducts with proteins through nucleophilic attack of amino groups in proteins on the BL ring. Allergenic determinants have been described for all BLs, although benzylpenicillin is the most widely studied. Moreover, formation of BL-protein adducts is selective, as we recently demonstrated for amoxicillin, which mainly modifies albumin, transferrin, and immunoglobulin heavy and light chains in human serum. Given the complexity of BL allergy, understanding the immunological mechanisms involved and optimization of diagnostic methods require multidisciplinary approaches that take into account the chemical structures of the drugs and the carrier molecules, as well as the patient immune response.

Hypersensitivity reactions to ß-lactams: relevance of hapten-protein conjugates

B-Lactams (BL) are the drugs most frequently involved in allergic reactions. They are classified according to their chemical structure as penicillins, cephalosporins, monobactams, carbapenems, and clavams. All BL antibiotics have a BL ring that is fused to a 5-member or 6-member ring (except in monobactams) and has 1, 2 or 3 side chains (except in clavams). Differences in chemical structure mean that a wide range of BLs are recognized by the immune system, and patients may experience clinical reactions to one BL while tolerating others. Diagnosis is based on skin and in vitro testing, although both display low sensitivity, possibly because they are based on drugs or drug conjugates that are not optimally recognized by the immune system. BLs are haptens that need to bind to proteins covalently to elicit an immune response. These drugs have a high capacity to form covalent adducts with proteins through nucleophilic attack of amino groups in proteins on the BL ring. Allergenic determinants have been described for all BLs, although benzylpenicillin is the most widely studied. Moreover, formation of BL-protein adducts is selective, as we recently demonstrated for amoxicillin, which mainly modifies albumin, transferrin, and immunoglobulin heavy and light chains in human serum. Given the complexity of BL allergy, understanding the immunological mechanisms involved and optimization of diagnostic methods require multidisciplinary approaches that take into account the chemical structures of the drugs and the carrier molecules, as well as the patient immune response (AU)

Las betalactamas (BL) son los fármacos implicados más frecuentemente en reacciones alérgicas. Se clasifican según su estructura química en penicilinas, cefalosporinas, monobactamas, carbapenems y clavamas. Poseen un anillo betalactámico que, excepto en las monobactamas, está fusionado a un anillo de cinco o seis miembros y, excluyendo las clavamas, tienen 1, 2 o 3 cadenas laterales. Las diferencias en las estructuras químicas resultan en un amplio rango de BLs, que puede ser discriminado por el sistema inmune, con inducción de reacciones clínicas a una BL y tolerancia a otras. El diagnóstico está basado en pruebas cutáneas e in vitro, aunque ambas presentan una baja sensibilidad. Esto podría deberse a que los fármacos o conjugados de fármacos empleados en estos tests que no se reconocen de manera óptima por el sistema inmune. Las BLs son haptenos que necesitan de su unión covalente a proteínas para inducir una respuesta inmunológica. Estos fármacos presentan una elevada capacidad para formar aductos covalentes con proteínas mediante el ataque nucleofílico de grupos aminos de proteínas al anillo BL. Aunque la bencilpenicilina ha sido la mejor estudiada, también se han descrito determinantes alergénicos del resto de BLs. Además, la formación de los aductos BLs-proteína muestra selectividad, así se ha demostrado recientemente para la amoxicilina, que principalmente modifica la albúmina en suero (HSA), la transferrina y las cadenas ligeras y pesadas en suero humano. Dada la complejidad de la alergia a BL, el conocimiento de los mecanismos inmunológicos implicados y la optimización de los métodos diagnósticos requieren de abordajes multidisciplinares teniendo en cuenta tanto la estructura química de los fármacos y de las moléculas portadoras, como las respuestas de los pacientes (AU)

Panchromatic symmetrical squaraines: a step forward in the molecular engineering of low cost blue-greenish sensitizers for dye-sensitized solar cells.

Two novel symmetrical blue squaraine sensitizers were synthesized, which exhibit panchromatic light harvesting and a record efficiency over 6% with Jsc exceeding 14 mA cm(-2), and Voc over 620 mV under 1 sun. Their color, low cost, easiness of synthesis, and relatively high photo- and thermal stability open up the way for commercial applications.

[Eco-toxicological study conducted with a battery of biological and phytological tests on sediments carried out on a series of 24 tributaries of the Po in 1994 and 1995]. / Ricerche ecotossicologiche eseguite con batterie di tests biologici e fitologici sui sedimenti prelevati in sequenza da 24 fiumi affluenti del Po, negli anni 1994 e 1995.

In spring and autumn 1994 and 1995 affluent water and bed sediment were sampled from 24 tributaries of the Po river, always at the same site and at the nearest place to the confluence. In the laboratory the pore water was separated from the particle fraction of the sediment. The organic compounds bound to the latter component were extracted with solvents and brought to water solution by means of dimethyl sulfoxide. The observed animal species, along with the seeds of Lepidium, were exposed to effluent water, to pore water and to water solutions of the organic compounds extracted from bed sediment. Toxicity was evaluated on the basis of 1) direct lethality, 2) the delay of embryo development, 3) the impairment of regeneration, in the animal species, while the germination index was used for the Lepidium susceptibility. The results of these investigations demonstrate that 1) the challenged species cover a broad range of sensitivities toward environmental toxins, 2) toxicity found in river samples appears almost exclusively bound to the sediment, 3) the noxious effects found in the tributaries of the Po river increase moving downstream, and 4) likewise the sediment-bound toxicity varies among the different samplings, both as a consequence of changes in rain-dependent river flow, and because of the man-made interventions on the river sides and bed.

Subdural grid recordings of distributed neocortical networks involved with somatosensory discrimination.

Previous studies suggest that evidence for the sub-second activation of distributed neural networks can be obtained by computing the covariance between segments of the scalp-recorded evoked potential. However, the cortical representation of such potentials is not known. Here we report a case study where the evoked potential covariance (EPC) measure was applied to data recorded from a 58-channel subdural grid implanted in an epilepsy patient. Recordings were made while the patient performed a task that required judging the somatosensory intensities of electrical stimuli and executing precise finger flexion responses in response to a subset of those stimuli. Post-stimulus EPC patterns involved covariances between somatosensory, motor, and temporal regions. Pre-stimulus EPC patterns involved these same regions, but only when it could be anticipated that the upcoming stimulus would likely require a response. The majority of the observed EPCs occurred with non-zero time-lags, and these EPCs often involved non-adjacent electrode pairs. Thus, the observed EPCs were unlikely to arise solely from volume conduction. Rather, they appeared to reflect the transient integration of activity across distinct cortical processing nodes.