1,721,056 research outputs found
Supramolecular Sensing with Phosphonate Cavitands
No full textMolecular recognition is a recurrent theme in chemical sensing because of the importance of selectivity for sensor performances. The popularity of molecular recognition in chemical sensing has resulted from the progress made in mastering weak interactions, which has enabled the design of synthetic receptors according to the analyte to be detected.
However, the availability of a large pool of modular synthetic receptors so far has not had a significant impact on sensors
used in the real world. This technological gap has emerged because of the difficulties in transferring the intrinsic molecular
recognition properties of a given receptor from solution to interfaces and in finding high fidelity transduction modes for the
recognition event. This Account focuses on the ways to overcome these two bottlenecks, and we recount our recent efforts to
produce highly selective supramolecular sensors using phosphonate cavitands as receptors. Through two examples, we
present an overview of the different operating strategies that are implemented depending on whether the interface is vapor-solid or liquid-solid.
First we describe the selective detection of short chain aliphatic alcohols in the vapor phase. In this example, we solved a key
issue common to all sensors for organic vapors: the dissection of the specific interaction (between cavitand and the alcohol) from
ubiquitous nonspecific dispersion interactions (between the analytes and interferents in the solid layer). We removed responses resulting from the nonspecific interactions of the analytes with interferents by directly connecting the recognition event at the interface to the transduction mechanism (photoinduced charge transfer).
The second example addresses the specific detection of sarcosine in urine. Recent research has suggested that sarcosine can serve as reliable biomarker of the aggressive forms of prostate cancer. Tetraphosphonate cavitands can complex N-methyl ammonium salts with impressive selectivity in solution, and we used this property as a starting point.
The sensor implementation requires that we first graft the cavitand onto silicon and gold surfaces as monolayers. The
exclusive recognition of sarcosine by these supramolecular sensors originates from their operation in aqueous environments, where synergistic multiple interactions with the phosphonate cavitand are possible only for N-methyl ammonium derivatives. We couple that selectivity with detection modes that probe the strength of the complexation either directly (microcantilever) or via exchange with molecules that have comparable affinity for the cavity (fluorescence dye dispacement)
Impiego di un Sistema Olfattivo Artificiale (SOA ) per il controllo della conservabilità della carne di lumaca
No full textLa richiesta sul mercato di prodotti a base di carne di lumaca è aumentata in maniera rilevante in questi ultimi 10 anni; in particolare tale aumento è ascrivibile a lumache commercializzate vive. Il controllo ufficiale di questo prodotto si avvale tuttora della valutazione organolettica della freschezza, facilmente applicabile dagli operatori sanitari ma con il limite di essere soggettiva. In questo lavoro si descrive l’impiego di un Sistema Olfattivo Artificiale (SOA) allo scopo di monitorare, in maniera obiettiva, lo sviluppo dell’odore durante la conservazione di carne di lumaca a +5°C per
14 giorni. Sottoponendo i dati così ottenuti ed elaborandoli con la tecnica dell’analisi multivariate (PCA), è stato possibile separare i dati in tre classi, con un tasso di discriminazione anche del 99,5%.
Questa classificazione ha permesso di determinare la qualità del campione analizzato in funzione del tempo e delle condizioni di conservazione
Nitrosonium complexation by the tetraphosphonate cavitand 5,11,17,23-tetramethyl-6,10:12,16:18,22:24,4-tetrakis(phenylphosphonato-κ2O,O)resorcin(4)arene
Full text linkThe crystal structure of a new supramolecular complex between the tetraphosphonate cavitand 5,11,17,23-tetramethyl-6,10:12,16:18,22:24,4-tetrakis(phenylphosphonato-κ2O,O′)resorcin(4)arene and the nitrosyl cation NO+, as the BF4− salt, is reported. The complex, of general formula [(C56H44P4O12)(NO)]BF4·CH2Cl2 or NO@Tiiii[H, CH3, C6H5] BF4·CH2Cl2, crystallizes in the space group P-1. The nitrosyl cation is disordered over two equivalent positions, with occupancies of 0.503 (2) and 0.497 (2), and interacts with two adjacent P=O groups at the upper rim of the cavitand through dipole–charge interactions. In the lattice, the cavitands are connected through a series of C—H...π interactions involving the methyl and methylenic H atoms and the aromatic rings of the macrocycle. The structure is further stabilized by the presence of C—H...F interactions between the hydrogen atoms of the cavitands and the F atoms of the tetrafluoridoborate anion. As a result of the disorder, the lattice dichloromethane molecules could not be modelled in terms of atomic sites, and were treated using the PLATON SQUEEZE procedure [Spek (2015). Acta Cryst. C71, 9–18]. The complexation process has also been studied in solution through NMR titrations
Biochemical sensing with macrocyclic receptors
Full text linkPreventive healthcare asks for the development of cheap, precise and non-invasive sensor devices for the early detection of diseases and continuous population screening. The actual techniques used for diagnosis, e.g. MRI and PET, or for biochemical marker sensing, e.g. immunoassays, are not suitable for continuous monitoring since they are expensive and prone to false positive responses. Synthetic supramolecular receptors offer new opportunities for the creation of specific, selective and cheap sensor devices for biological sensing of specific target molecules in complex mixtures of organic substances. The fundamental challenges faced in developing such devices are the precise transfer of the molecular recognition events at the solid-liquid interface and its transduction into a readable signal. In this review we present the progress made so far in turning synthetic macrocyclic hosts, namely cyclodextrins, calixarenes, cucurbiturils and cavitands, into effective biochemical sensors and the strategies utilized to solve the above mentioned issues. The performances of the developed sensing devices based on these receptors in detecting specific biological molecules, drugs and proteins are critically discussed
Formaggio a pasta dura a basso contenuto di sale
No full textL’eccessiva assunzione di sodio con la dieta è stata
documentata recentemente, su basi scientifiche, come
tra i fattori di rischio per le patologie cardiovascolari. Il
Regno Unito è tra i principali Paesi che stanno adottando
diverse strategie per la riduzione di sodio negli alimenti
a più largo consumo. Tuttavia la riduzione di sale
comporta inevitabilmente un effetto sfavorevole sulle
qualità organolettiche e sul sapore. Anche nei formaggi
a pasta dura e a lunga stagionatura il sale gioca un
ruolo importante oltre che nella conservazione anche
e soprattutto nel determinare le caratteristiche legate
alla gradevolezza. In questo studio vengono riportate
le analisi effettuate su campioni di formaggio a pasta
dura (GranSpeciale) con un contenuto di sale normale
e campioni dello stesso formaggio a contenuto ridotto
(-35%). L’impiego di un Sistema Artificiale Olfattivo (SOA)
ha permesso di verificare che il profilo aromatico dei
campioni presi in esame risulta pressoché sovrapponibile
(livello di discriminazione del 62,1%)
Method for detecting small molecules by means of monolayer protected gold nanoparticles covered noncovalently with macrocyclic receptors
No full textA modular indicator-displacement-assay is presented able to selectively recognize small molecules with biological relevance under competitive conditions. The assay relies on the change in affinity of macrocyclic receptors for a monolayer protected gold nanoparticles upon complexation of the respective target analyte. This change affects the equilibrium between the nanoparticles and a fluorescent reporter leading towards a change in intensity of the fluorescent output signal. The recognition modules can be changed in order to tune the selectivity of the assay without affecting the nature of the output signal. The combined use of recognition modules results in an assay able to detect multiple analytes simultaneously with high selectivity
AN ADHESIVE COMPOSITION CONTAINING POLYETHYLENE BASED IONOMERS
No full textThe invention relates to an ethylene polymer based adhesive composition. The invention further relates to an adhesive composition comprising an ethylene polymer comprising polymeric units derived from ethylene and ion pair compounds. In addition, the invention relates to the use of adhesive composition in the adhesion of the layers of a multi-articl
Polyethylene ionomers as thermally reversible and aging resilient adhesives
Full text linkLow-density Polyethylene (LDPE) is a widely used thermoplastic polymer in various industries due to its
versatility and cost-effectiveness. However, its inherent limitations, including low strength, poor UV resistance,
and poor adhesion properties, have spurred efforts to enhance its applicability. We recently developed a LDPE
ionomer based on ion pair comonomers (IPC) that can extend the range of application where traditional LDPE are
limited. In this work, we report the effect of the reaction conditions on IPC content and melt flow index (MFI) for
the PE ionomer obtained by copolymerizing ethylene with the ion pair dimethyl-amino methacrylate and
methacrylic acid. The resulting ionomers exhibited improved mechanical properties, including higher elongation
and stress at break, making them superior to conventional LDPE. The developed ionomers display enhanced
adhesion properties on aluminum substrates with respect to LDPE. Remarkably, the adhesives exhibit thermal
reversibility, making them suitable for applications requiring disassembly. Accelerated aging tests demonstrate
the ionomers’ durability, with some even showing increased adhesion after exposure to harsh conditions.
Overall, this study highlights the potential of PE-based ionomers as advanced materials that combine the benefits
of thermosets and thermoplastics, while offering outstanding adhesive properties when the IPC content is higher
than 1 mol %
Reliability of the TTC approach: Learning from inclusion of pesticide active substances in the supporting database
No full textData on pesticide active substances were used to assess the reliability of the Threshold of Toxicological
Concern (TTC) approach. Pesticides were chosen as a robust test because of their potential for toxicity.
328 pesticide substances were classified on the basis of their chemical structure, according to the generic
scheme proposed by the European Food Safety Authority. 43 carbamates and organophosphates were
allocated to the group for neurotoxicity alerts, and 279 substances to Cramer structural Class III. For Class
III, the 5th percentile value as calculated from the cumulative distribution curve of the no-observedeffect
levels (0.20 mg/kg bw per day), was slightly higher than that determined by Munro (0.15 mg/kg
bw per day) from his original database. The difference is explained by the inclusion of carbamates and
organophosphates in Munro’s Class III. Consideration of the acceptable daily intakes and their underlying
toxicity data showed that the TTC approach is conservative for 96.2% of the substances. Overall, this
analysis gives added support to the utility of the generic scheme of application of the TTC approach for
hazard assessment of substances for which few or no experimental toxicity data are available. A convenient
alternative to the Cramer decision tree is proposed
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