In the last few decades, mechanochemistry has become rapidly established as a powerful tool enabling environmentally-benign and sustainable chemical syntheses. Not only have these techniques been ...demonstrated as viable alternatives to traditional solution-based syntheses, but they have also received attention for their ability to enable new reactivity and "unlocking" novel compounds inaccessible by conventional methods. Reflecting the rising popularity of mechanochemistry, many excellent reviews highlighting its benefits have recently been published. Whilst the scope of most of these focuses on organic chemistry, transition-metal catalysis, porous framework materials, coordination compounds and supramolecular synthesis, few have addressed the use of mechanochemical ball milling for the synthesis of compounds containing s- and p-block elements. This tutorial review turns the spotlight towards mechanochemical research in the field of inorganic main group chemistry, highlighting significant advantages that solid-state inorganic reactions often possess, and the potential for these to drive the development of greener methodologies within the modern main group arena.
Mechanochemical Rearrangements Virieux, David; Delogu, Francesco; Porcheddu, Andrea ...
Journal of organic chemistry,
10/2021, Letnik:
86, Številka:
20
Journal Article
Recenzirano
Molecular rearrangements are a powerful tool for constructing complex structures in an atom- and step-economic manner, translating multistep transformations into an intrinsically more sustainable ...process. Mechanochemical molecular rearrangements become an even more appealing eco-friendly synthetic approach, especially for preparing active pharmaceutical ingredients (APIs) and natural products. Still in their infancy, rearrangements promoted by mechanochemistry represent a promising approach for chemists to merge molecular diversity and green chemistry perspectives toward more selective and efficient syntheses with a reduced environmental footprint.
Elastin-like polypeptides (ELPs) with the repeat sequence of VPGVG are widely used as a model system for investigation of lower critical solution temperature (LCST) transition behavior. In this ...paper, the effect of temperature on the structure, dynamics and association of (VPGVG)18 in aqueous solution is investigated using atomistic molecular dynamics simulations. Our simulations show that as the temperature increases the ELP backbones undergo gradual conformational changes, which are attributed to the formation of more ordered secondary structures such as β-strands. In addition, increasing temperature changes the hydrophobicity of the ELP by exposure of hydrophobic valine-side chains to the solvent and hiding of proline residues. Based on our simulations, we conclude that the transition behavior of (VPGVG)18 can be attributed to a combination of thermal disruption of the water network that surrounds the polypeptide, reduction of solvent accessible surface area of the polypeptide, and increase in its hydrophobicity. Simulations of the association of two (VPGVG)18 molecules demonstrated that the observed gradual changes in the structural properties of the single polypeptide chain are enough to cause the aggregation of polypeptides above the LCST. These results lead us to propose that the LCST phase behavior of poly(VPGVG) is a collective phenomenon that originates from the correlated gradual changes in single polypeptide structure and the abrupt change in properties of hydration water around the peptide and is a result of a competition between peptide–peptide and peptide–water interactions. This is a computational study of an important intrinsically disordered peptide system that provides an atomic-level description of structural features and interactions that are relevant in the LCST phase behavior.
Given the need to understand both the negative and positive psychological consequences of the current global COVID-19 pandemic (Brewin et al. in Perspectives in Public Health
...https://doi.org/10.1177/1757913920957365
2020), the aim of this study was to test a cognitive model of post-traumatic symptoms (PTS) and post-traumatic growth (PTG) during confinement caused by the SARS-COV-2 epidemic. In line with cognitive models of trauma elaboration (Park in Psychological Bulletin
https://doi.org/10.1037/a0018301
), we included in our model some beliefs associated to the world (e.g., primal beliefs about a good world), to the self (e.g., death anxiety or orientation toward the future) and to others (e.g., suspiciousness or identification with humanity). To evaluate the explanatory model, a national representative sample of adults between the ages of 18 and 75 (N = 1951) was surveyed between 7th and 13th April, 2020, in the middle of a strict 7-week national confinement. Structural equation modelling yielded a very similar model to the one initially specified. The results highlight the role of both negative and positive core beliefs, which are pertinent to the current pandemic threat, in the appearance of PTS and PTG, respectively. In short, primal beliefs about a good world, openness to the future and identification with humanity were associated with PTG; while suspiciousness, intolerance of uncertainty, anxiety about death and also identification with humanity were associated with PTS and consequent impairment. This is an innovative study of different pathways to traumatic responses and growth during a pandemic. Future research is needed to replicate its findings.
This paper reports a new strategy, recursive directional ligation by plasmid reconstruction (PRe-RDL), to rapidly clone highly repetitive polypeptides of any sequence and specified length over a ...large range of molecular weights. In a single cycle of PRe-RDL, two halves of a parent plasmid, each containing a copy of an oligomer, are ligated together, thereby dimerizing the oligomer and reconstituting a functional plasmid. This process is carried out recursively to assemble an oligomeric gene with the desired number of repeats. PRe-RDL has several unique features that stem from the use of type IIs restriction endonucleases: first, PRe-RDL is a seamless cloning method that leaves no extraneous nucleotides at the ligation junction. Because it uses type IIs endonucleases to ligate the two halves of the plasmid, PRe-RDL also addresses the major limitation of RDL in that it abolishes any restriction on the gene sequence that can be oligomerized. The reconstitution of a functional plasmid only upon successful ligation in PRe-RDL also addresses two other limitations of RDL: the significant background from self-ligation of the vector observed in RDL, and the decreased efficiency of ligation due to nonproductive circularization of the insert. PRe-RDL can also be used to assemble genes that encode different sequences in a predetermined order to encode block copolymers or append leader and trailer peptide sequences to the oligomerized gene.
Several mechanochemically heated processes have been published in recent years. However, precise control over the mechanochemical catalysed coupling reactions remained elusive. A recent report from ...Leitch, Browne and co‐workers demonstrated how a programmable jar heater manifold delivers an efficient methodology for the Suzuki–Miyaura‐type cross coupling reaction of aryl sulfamates and aryl boronic acid species. This methodology can be readily upscaled 200‐fold using twin‐screw extrusion methodologies.
A recent report from Leitch, Browne and co‐workers demonstrated how a programmable jar heater delivers an efficient methodology for the Suzuki–Miyaura‐type cross coupling reaction of aryl sulfamates and aryl boronic acid species. This methodology can be readily upscaled 200‐fold using twin‐screw extrusion methodologies, demonstrating scalability of mechanochemical catalytic processes.
The Brief-COPE is an abbreviated version of the COPE (Coping Orientation to Problems Experienced) Inventory, a self-report questionnaire developed to assess a broad range of coping responses. ...Currently, it is one of the best validated and most frequently used measures of coping strategies. The aim of this study was to validate a culturally appropriate Chilean version of the Brief-COPE, assess its psychometric properties and construct and congruent validity. The Spanish version of the Brief-COPE was administrated in a community sample of 1847 Chilean adult (60.4% women) exposed to a variety of stressful experiences. The factorial structure of the inventory was examined by comparing four different models found in previous studies in Latin American population. The results of confirmatory factor analyses revealed, as in the original studies, a 14-factor structure of the Brief-COPE. These dimensions showed adequate internal structure and consistency. The factorial invariance comparing women and men confirmed strict invariance. Additionally, the results showed significant correlation between some Brief-COPE scales, such as denial and substance use, with perceived stress and emotional support and active coping with subjective well-being. Overall, the present work offers a valid and reliable tool for assessing coping strategies in the Chilean population.
•The new antigen test is an indispensable tool in the control of the pandemic due to its adequate sensitivity and specificity.•The implementation of the point of care technique in primary care is ...feasible and has good results.•Results of the antigen techniques are determined by an onset of symptoms inferior to five days and a CT below 27 in PCR.
RT-qPCR is the current recommended laboratory method to diagnose SARS-CoV-2 acute infection, several factors such as requirement of special equipment, time consuming, high cost and skilled staff limit the use of these techniques. A more rapid and high-throughput method is essential.
We analyzed clinical data and nasopharyngeal samples, collected during September 2020, from patients attended at the emergency department of a secondary hospital and in two primary healthcare centers in Madrid. The performance of the Panbio™ COVID-19 AG Rapid Test Device for the detection of SARS-CoV-2 antigen was compared to RT-qPCR.
255 nasopharyngeal swabs, including 150 from the emergency department and 105 from primary helthcare centers, were tested. 184 patients were symptomatic (72.1 %). Amongst the 60 positive RT-qPCR samples, 40 were detected by the rapid antigen test, given an overall sensitivity of 73.3 %. All the samples detected positive with the rapid antigen test were also positive with RT-qPCR. The median cycle threshold was 23.28 (IQR 18.5–30.16). Patients with less than seven days onset of symptoms showed a higher viral load, and sensitivity for rapid antigen test (86.5 %), compared to those with more days (sensitivity of 53.8 %)(p < 0.004).
The rapid antigen test evaluated in this study showed a high sensitivity and specificity in samples obtained during the first week of symptoms and with high viral loads. This assay seems to be an effective strategy for controlling the COVID-19 pandemic for the rapid identification and isolation of SARS-CoV-2 infected patients.
Toxic cyanobacterial blooms are globally increasing with negative effects on aquatic ecosystems, water use and human health. Blooms' main driving forces are eutrophication, dam construction, urban ...waste, replacement of natural vegetation with croplands and climate change and variability. The relative effects of each driver have not still been properly addressed, particularly in large river basins. Here, we performed a historical analysis of cyanobacterial abundance in a large and important ecosystem of South America (Uruguay river, ca 1900 km long, 365,000 km2 basin). We evaluated the interannual relationships between cyanobacterial abundance and land use change, river flow, urban sewage, temperature and precipitation from 1963 to the present. Our results indicated an exponential increase in cyanobacterial abundance during the last two decades, congruent with an increase in phosphorus concentration. A sharp shift in the cyanobacterial abundance rate of increase after the year 2000 was identified, resulting in abundance levels above public health alert since 2010. Path analyses showed a strong positive correlation between cyanobacteria and cropland area at the entire catchment level, while precipitation, temperature and water flow effects were negligible. Present results help to identify high nutrient input agricultural practices and nutrient enrichment as the main factors driving toxic bloom formation. These practices are already exerting severe effects on both aquatic ecosystems and human health and projections suggest these trends will be intensified in the future. To avoid further water degradation and health risk for future generations, a large‐scale (transboundary) change in agricultural management towards agroecological practices will be required.
Las floraciones de cianobacterias tóxicas vienen aumentando drásticamente a nivel mundial con efectos negativos en los ecosistemas acuáticos, los usos del agua y la salud humana. Los principales mecanismos promotores de las floraciones son la eutrofización, la construcción de represas, la contaminación con residuos urbanos, la pérdida de vegetación natural y el cambio y la variabilidad climáticos. Los efectos relativos de cada determinante aún no se han abordado adecuadamente, particularmente en las grandes cuencas fluviales de América del Sur. En este trabajo, realizamos un análisis histórico de la abundancia de cianobacterias en un gran e importante ecosistema de América del Sur (el Río Uruguay, c.a. 1.900 km de largo, cuenca de 365.000 km2). Evaluamos las relaciones entre la abundancia de cianobacterias y el cambio en los usos del suelo, el caudal de los ríos, la contaminación urbana, la temperatura y la precipitación desde 1963 hasta el presente. Nuestros resultados evidencian un aumento exponencial en la abundancia de cianobacterias durante las últimas dos décadas, de forma congruente con el aumento en la concentración de fósforo en agua. Fue identificado además, un cambio brusco en la tasa de aumento de la abundancia de cianobacterias después del año 2000, lo que resultó en niveles de alerta por encima de riesgo para la salud pública desde 2010. Los análisis estadísticos indicaron una fuerte y positiva correlación entre las cianobacterias y el área de cultivo en la cuenca, mientras que la precipitación, la temperatura y el flujo de agua fueron insignificantes. Estos resultados contribuyen a identificar que las prácticas agrícolas con alto aporte de nutrientes y el enriquecimiento de nutrientes son los principales impulsores de la formación de floraciones tóxicas. Estas prácticas ya están teniendo graves efectos en los ecosistemas acuáticos y la salud humana y las proyecciones sugieren que se intensificarán en el futuro. Para evitar una mayor degradación de la calidad del agua y el incremento de los riesgos para la salud de las generaciones futuras, se requerirá un cambio a gran escala (transfronterizo) en la gestión agrícola hacia prácticas agroecológicas.
Toxic cyanobacterial blooms are globally increasing with negative effects on aquatic ecosystems, water use and human health. Here we show that cyanobacterial abundance increased exponentially during the last six decades in a large river in South America. This was the result of the increase in intensive agriculture cropland area. Climatic and hydrological effects were insignificant. Our results contribute to disentangle bloom‐driving causes and to define management actions towards agroecological practices.
The bis(amidinato)-heavier tetrylenes E(bzamP)2 (E = Ge (2a) and Sn (2b); bzamP = N-isopropyl-N′-(diphenylphosphanylethyl)benzamidinate), which are equipped with one heavier tetrylene (germylene ...or stannylene) and two phosphane fragments (one on each amidinate moiety) as coordinable groups, have been synthesized from the benzamidinum salt H2bzamPCl and GeCl2(dioxane) or SnCl2 in 2:1 mol ratio. A preliminary inspection of their coordination chemistry has shown that their amidinate group can also be involved in the bonding with the metal atoms as tridentate ENP and tetradentate PENP′ coordination modes have been observed for the ECl(bzamP)2 ligand of Ir{κ3 E,N,P-ECl(bzamP)2}(cod) (E = Ge (3a) and Sn (3b); cod = η4-1,5-cyclooctadiene) and the E(bzamP)2 ligand of Ni{κ4 E,N,P,P′-E(bzamP)2} (E = Ge (4a) and Sn (4b)), which are products of reactions of 2a and 2b with IrCl(cod)2 (1:0.5 mol ratio) and Ni(cod)2 (1:1 mol ratio), respectively. These products contain a 5-membered NCNEM ring that results from the insertion of the metal M atom into an E–N bond of 2a and 2b. Additionally, while iridium(I) complexes 3a and 3b are chloridotetryl derivatives (insertion of the tetrylene E atom into the Ir–Cl bond has also occurred) that have an uncoordinated phosphane group, nickel(0) complexes 4a and 4b contain a tetrylene fragment that, maintaining the lone pair, behaves as a σ-acceptor (Z-type) ligand.
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