Photoswitchable catalysis by a nanozyme mediated by a lightsensitive cofactor

The activity of a gold nanoparticle-based catalyst can be reversibly up- and down-regulated by light. Light is used to switch a small molecule between cis- and trans-isomers, which inhibits the catalytic activity of the nanoparticles to different extent. The system is functional in aqueous buffer, which paves the way for integrating the system in biological networks

Desenvolupament d'un projecte de rec artificial per a un circuït de proves de motor

Aquest projecte tracta el disseny de les instal·lacions necessàries per implantar un sistema de rec artificial sobre la pista d’un circuit de carreres, en concret el Circuit de Barcelona-Catalunya. Es dissenya la instal·lació hidràulica de rec, es distribueixen dipòsits, s'amplia la xarxa de drenatge existent i es determinen les dimensions d’una depuradora pel tractament de l’aigua recollida tant de la pluja com del propi rec. Un dels criteris més importants és la recuperació de la màxima quantitat possible d’aigua utilitzada. Es realitza el càlcul i justificació de les dimensions de les instal·lacions necessàries i s’elaboren els diferents plànols que defineixen completament i sense ambigüitat les obres i modificacions a realitzar en el circuit. A més, el projecte compta amb documents típics d’un projecte executiu com el plec de condicions i el pressupost, on es realitza una anàlisi dels costos i el període de retorn de la inversió. Es duu a terme, també, un estudi de la portabilitat del projecte a d’altres latituds del globus, permetent una aproximació del cost total de les instal·lacions en dependència amb la localització del circuit. El resultat és un projecte complet capaç de caracteritzar tots els aspectes i detalls esperats d'un projecte d’instal·lacions, preparat per la realització de les obres projectades per complir els principals objectius

Dynamic Nanoproteins: Self-Assembly of Peptides on Monolayer Protected Gold Nanoparticles

Protein-protein interactions mediate a large number of important regulatory pathways in the organism and also play a central role in many pathologies. Protein surface recognition provides a powerful tool for the regulation of those protein-protein interactions. Gold nanoparticles offer a suitable platform for multi-functionalization with a wide range of biological ligands for the selective binding and detection of biological targets such as proteins. In particular, gold nanoparticles functionalized with peptide fragments are very attractive for that purpose, since peptides contain all necessary chemical information to interact with natural proteins. During the past years, self-assembly, i.e. the spontaneous organization of molecules into ordered aggregates, has emerged as the most attractive way to develop highly complex nanosized systems. Au NPs containing 1,4,7-triazacyclononane (TACN)·Zn(II) head groups (Au NP 1) have been shown to be attractive scaffolds for the formation of multivalent supramolecular structures. In this PhD-project the self-assembly of small peptides on monolayer protected gold nanoparticles has been studied as a means to develop dynamic nanoproteins for application in biomolecular recognition and catalysis. The first part has been dedicated to the identification and optimization of small peptides able to bind with high affinity to the surface of Au NP 1, which are gold nanoparticles (d ∼ 2 nm) covered with a monolayer of C9-thiols containing a 1,4,7-triazacyclonane•Zn(II) head group. The results showed four potential candidates of which the tripeptide LWS(p) (S(p) = phosphoserine) had the highest affinity. From a series of studies in which the metal-ion in the monolayer was varied, it emerged that Zn(II) gave the best results. Using LWS(p) as a lead structure a small peptide library was synthesized successively in which additional amino acid residues were attached to the binding unit. Amino acids containing negatively or positively charged, polar and apolar side chains were chosen in order to create a chemical diverse library. Subsequent binding studies showed that all peptides had a very high affinity for Au NP 1, apart from the peptides containing positively charged amino acids. Subsequently, the peptide library was used to self-assembly a dynamic nanoprotein by adding all peptides simultaneously to Au NP 1. Binding studies revealed that binding occurred under saturation conditions at low micromolar concentrations in aqueous buffer at pH = 7. The addition of a competitor for binding resulted in a complete displacement of the peptides demonstrating the dynamic nature of the surface. In this way it has been demonstrated that it is possible to build up a complex multivalent system in a straightforward manner. The dynamic nature of the system was exploited in a series of self-selection experiments, aimed at determining how the surface composition on Au NP 1 would change when an excess of peptides would be present. A new protocol relying on the use of ultracentrifugation filters containing a MW cut-off membrane was developed for the purpose of analyzing the surface composition. The results showed a spontaneous self-selection of the peptides with a higher affinity for Au NP 1 upon increasing the overall concentration of the peptide library. In the next stage, the ability of the nanoprotein to interact with natural protein surfaces was investigated. A particular attention was paid to exploitation of the dynamic nature of the assembly. The serine protease chymotrypsin (ChT) was chosen as a target, because previous literature reports had already mentioned that peptide-functionalized Au NPs are able to bind ChT. Binding assays confirmed that the presence of ChT did not affect the interaction between the peptide library and Au NP 1. Apart from peptide P2, none of the peptides was hydrolyzed by ChT. Enzyme activity studies in the presence of Au NP 1-peptide systems did not provide conclusive data. The obtained data showed a slight activation of ChT (1.5 times) in the presence of Au NP, irrespective of whether peptides were present or not. Such an activation of ChT by cationic agents has also been reported in other studies, but a clear explanation is not yet available. Since the measurement of enzyme activity is an indirect method of measuring the interaction between the nanoproteins and ChT, the attention was shifted towards a direct method relying on the ultracentrifugation experiments developed earlier. The aim was to investigate whether the surface composition would be affected by the addition of ChT. Initial data from the ultracentrifugation experiments and additional fluorescence studies seemed to suggest the formation of a ternary multivalent complex with peptide P1 sandwiched between Au NP 1 and ChT. However, further experiments under different conditions and including other techniques (such as ITC and DLS) are required to confirm these results. Finally, a collaboration with the Ulijn group at the University of Strathclyde led to a detailed investigation of the activity of Au NP 1 as artificial phosphatases. The original idea was to exploit the high affinity of peptides for Au NP 1 to shift the equilibrium of a dynamic system of interconverting peptides (catalyzed by thermolysin). However, initial studies immediately revealed that after some days the nanoparticles-enzyme mixture caused the dephosphorylation of Fmoc-Yp-OH. This observation led to an in depth study of the origin of this reaction. Initial experiments performed at high concentrations pointed to thermolysin as the prime responsible for the dephosphorylation reaction assisted by Zn(II) or Au NP 1. Under these conditions hardly any activity by Au NP 1 was observed. However, the picture changed completely when the kinetic studies were repeated at much lower (micro)molar concentrations. Now, a strong catalytic activity of Au NP 1 was detected. Indeed, at conditions, i.e. Fmoc-Yp-OH closer to the SSC of Au NP 1, only 10 hours were needed to convert 50% of substrate. Although for a precise understanding of the mechanism more studies are required, the fact that Au NP 1 is able to cause the dephosphorylation of a monophosphate is a very exciting result, considering that the catalytic activity of Au NP 1 and related systems has so far mainly been limited to activated phosphodiesters

Variation in the size of eggs of Kelp Gulls (Larus dominicanus) at two colonies in Patagonia, Argentina

Although several studies have reported basic information about the size of Kelp Gull (Larus dominicarius) eggs, no attention has been paid to the comparison of patterns of intra-clutch variation at different breeding sites. Here, the variation in egg size of Kelp Gulls at two colonies from Patagonia, Argentina, was analyzed. The objectives were to characterize egg size variation in Kelp Gulls breeding at a recently established colony in Punta Loma that primarily relies on natural prey; and to evaluate if patterns of intra-clutch variation in that colony differ from those at Vernaci Sudoeste Island, a larger and well-established colony with access to supplementary food in the form of fishery waste. In two-egg clutches, first-eggs were larger than second-eggs. Neither average egg size nor intra-clutch patterns differed between study sites. Also, in two-egg clutches, egg size decreased as date of laying increased, probably due to younger birds laying smaller eggs later in the season. The pattern of intra-clutch variation in three-egg clutches differed between sites. Three-egg clutches at Vernaci Sudoeste Island presented similar sizes for first- and second-eggs and these were larger than third-eggs. This pattern contrasted with the steady decrease in relation to laying order that was observed at Punta Loma. Also, second-and third-eggs from Vernaci Sudoeste Island were larger than corresponding eggs from Punta Loma. Our data suggest that differences in egg size between colonies could be the consequence of enhanced food availability at Vernaci Sudoeste Island in the form of discards generated by trawl fisheries. Future studies to evaluate age of birds and inter-annual environmental stochasticity are needed to elucidate the effect of these factors on egg size variationFil: Svagelj, Walter Sergio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencia Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; ArgentinaFil: Lisnizer, Nora. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; ArgentinaFil: Garcia Borboroglu, Jorge Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Centro para el Estudio de Sistemas Marinos; ArgentinaFil: Yorio, Pablo Martin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Centro para el Estudio de Sistemas Marinos; Argentin

Theory of Negative-Refractive-Index Response of Double-Fishnet Structures

A theory is presented of the negative refractive index observed in the so-called double-fishnet structures. We find that the electrical response of these structures is dominated by the cutoff frequency of the hole waveguide whereas the resonant magnetic response is due to the excitation of gap surface plasmon polaritons propagating along the dielectric slab. Associated with this origin, we show how the negative refractive index in these metamaterials presents strong dispersion with the parallel momentum of the incident light

Channel plasmon-polaritons: modal shape, dispersion, and losses

We theoretically study channel plasmon-polaritons (CPPs) with a geometry similar to that in recent experiments at telecom wavelengths (Bozhevolnyi et al., Nature 440, 508 (2006)). The CPP modal shape, dispersion relation, and losses are simulated using the multiple multipole method and the finite difference time domain technique. It is shown that, with the increase of the wavelength, the fundamental CPP mode shifts progressively towards the groove opening, ceasing to be guided at the groove bottom and becoming hybridized with wedge plasmon-polaritons running along the groove edges.Comment: 4 pages, 4 figure

Avionics System and Attitude Algorithms for a Deorbit Device Based on an Electrodynamic Tether

The main goal of the Electrodynamic Tether technology for PAssive Consumable-less deorbit Kit (E.T.PACK) project is to develop a deorbit device based on an electrodynamic tether with TRL 4 by 2022. In September 2022, its continuation, i.e. the E.T.PACK-F project, will carry on with the activities of E.T.PACK to prepare a flight model with TRL 8 that will be tested in an in-orbit demonstration mission in 2025. This work (i) describes the attitude determination and control strategy of the mission, which is used as a means of explaining its different phases and the dynamics of each one of them, (ii) provides a description of the avionics elements of the whole system, (iii) describes some of the tests performed until this moment, and (iv) summarizes the current status and the future work

Increased exposure to pesticides and colon cancer: Early evidence in Brazil

Environmental factors may increase colon cancer (CC) risk. It has been suggested that pesticides could play a significant role in the etiology of this malignancy. As agriculture is one of the mainstays of the Brazilian economy, this country has been the largest pesticides consumer worldwide. The CC burden is also increasing in Brazil. Herein, we examined data from the Brazilian Federal Government to determine whether CC mortality and pesticide consumption may be associated. Database of the Ministry of Health provided CC mortality data in Brazil, while pesticides use was accessed at the website of Brazilian Institute of Environment and Renewable Natural Resources. The CC mortality in the Brazilian states was calculated as standard mortality rates (SMR). All Bayesian analysis was performed using a Markov chain Monte Carlo method in WinBUGS software. We observed that colon cancer mortality has exhibited a steady increase for more than a decade, which correlated with the amount of sold pesticides in the country. Both observations are concentrated in the Southern and the Southeast regions of Brazil. Although ecological studies like ours have methodological limitations, the current dataset suggests the possibility that pesticide exposure may be a risk factor for colon cancer. It warrants further investigation

Topical Brazilian propolis improves corneal wound healing and inflammation in rats following alkali burns

Abstract\ud \ud \ud \ud Background\ud \ud The objective of this study was to investigate the effects of the Brazilian Scaptotrigona sp propolis, a widely used folk medicine, in corneal wound healing and inflammation.\ud \ud \ud \ud Methods\ud \ud Corneal epithelial defects of 1 mm in diameter were made in the right eyes of Wistar male adult rats by cauterization with silver nitrate sticks. Subsequently, they were divided in two groups (n = 40 rats/group): Brazilian propolis (BP) group was topically treated with a microemulsion containing 1% Brazilian propolis; vehicle (VH) group received the same formulation without propolis. The epithelial defect area was photographed and measured at t = 0 (wound induction), and after 12, 24, 48 and 120 h of treatment. The inflammatory response was evaluated based on counting of neutrophils. Epithelial regeneration rates were determined based on Ki-67 expression in basal epithelial cells. Comparisons were made using the Kruskal-Wallis and the Mann–Whitney U test.\ud \ud \ud \ud Results\ud \ud The BP group presented both smaller epithelial defect areas at 12, 24 and 48 h and fewer corneal infiltrating neutrophils at 24 and 48 h (P < 0.01) than the VH group. These effects were associated with more pervasive Ki-67 staining in the BP group at 12 and 24 h (P < 0.05).\ud \ud \ud \ud Conclusions\ud \ud Topically applied BP accelerated wound healing and reduced the inflammatory response to silver nitrate-induced corneal alkali burns in rats.The authors sincerely acknowledge Rosângela Orlandin Lopes, Mateus Freire Leite, Patrícia Modiano and Aline Turatti, of the Department of Pathology - Faculty of Medicine of Ribeirão Preto, University of São Paulo for their help with the histological preparations and photographs on this study. We also acknowledge the NIH Fellows Editorial Board for editorial assistance and Peter Sol Reinach for his careful assistance in the revision of the English grammar and style