8,896 research outputs found
Ligand and structure design of bio-inspired multi-electron redox catalysts
No full textThe water-to-oxygen redox couple, H2O/O2, powers our aerobic life through the fundamental processes of natural photosynthesis and cellular respiration. Despite its vital role, any failure of this four-electron mechanism turns out to release O2-derived toxic radicals, inducing a severe oxidative damages of any synthetic and biological materials exposed to the aerobic risk. The aerobic formation of ROS is due to oxygen reduction in-vivo, generating the superoxide anion (O2•–), hydrogen peroxide (H2O2), and the hydroxyl radical (HO•). ROS give rise to fast, barrier-less, short-range and non-selective oxidation steps, being responsible for the “oxidative stress”, a key factor for cellular death, organ failure and aging diseases. In addition photo-oxidative stress is one key factor limiting plant productivity, i.e. bio-mass and food yield. Noteworthy, ROS-forming mechanisms are also lethal for the stability of bio-inspired materials designed for artificial photosynthesis in vitro. The biological defense against ROS-induced cellular damage stems from the combined action of “anti-oxidant” metallo-enzymes, as superoxide dismutase (SOD), and catalase (CAT). A detoxification cascade occurs via SOD-induced dismutation of O2•– into O2 and H2O2 which is then converted by CAT into H2O and O2 again. In this thesis will be presented the design of a set of novel anti-oxidant catalysts, based on different metal centers, that can emerge by the engineering of a synzyme with integrated SOD/CAT activity able to mimic both the enzymes activities and efficiently perform a complete ROS scavenging also in biological-like solution. The activity of the synzymes will be also tested in water splitting processes to perform both the water oxidation than the proton reduction reactions in water at neutral pH, a key feature to obtain sustainable energy sources from water.
The obtained results will be divided in four main chapters:
- Chapter 2: coupling of a polycationic Mn(III)-porphyrin, with a dinuclear Mn2(II,II)L2 core results in a dual Superoxide Dismutase (SOD) and Catalase (CAT) functional analog, Mn2L2Pn+, enabling a detoxification cascade of the superoxide anion and hydrogen peroxide into benign H2O and O2. The SOD/CAT artificial manifolds, joined in one asset, exhibit a peak catalytic performance under physiological conditions, with log kcat(O2•–) ≥ 7 and kcat(H2O2)/KM = 1890. The dual-enzyme (di-zyme) concept allows for a unique, built-in-self-protection, against the irreversible bleaching of the porphyrin unit, (> 75% protection), readily induced by H2O2 (200 μM, 20 equivalents, in buffer solution, pH=7.8). We show herein that incubation of the photosynthetic green algae, Chlamydomonas reinhardtii, with the synthetic di-zyme (as low as 0.1 μM), prevents H2O2 accumulation under high-light illumination conditions, thus providing an efficient anti-oxidant surveillance and photo-protection.
- Chapter 3: dinuclear Cu(II)2L2 catalysts were synthesized and studied for their SOD/CAT activity. The goal of this study was to demonstrate that with a proper ligand set, is it possible tune the reactivity of an harmful metal like copper, turns it to a benign anti-oxidant system. The dinuclear copper complexes show SOD activity with logkcat up to 7.55 and CAT activity with rate of O2 production up to 4.4 μM/s. Kinetic studies of the process of hydrogen peroxide dismutation show also an evolution of the catalyst during the catalytic turnover. No evidence of oxidation of external substrates was also confirmed as consequence of the sacrificial internal scavenger.
- Chapter 4: novel Fe(III)L, Fe(III)2L2 and Co2(II)L2 complexes have also been isolated. Preliminary results indicate that a multi-redox manifold is available for both species, however with scarce activity as ROS scavenger. These complexes show instead an interesting activity in the water oxidation process. In addition the anodic waves observed in reduction are promising for catalytic proton reduction processes performed by using directly water as proton source.
- Chapter 5: application of oxygen evolving catalysts within functional materials has been explored in the field of porous membranes. This novel stimuli-responsive strategy against the irreversible fouling of porous materials and surfaces is based on the molecular design of catalytic pore walls that foster a chemo-mechanical, self-cleaning behaviour under neutral pH and mild conditions of pressure and temperature. To this aim, the catalase-like behaviour of the tetra-ruthenium substituted polyoxometalate, has been exploited for in-pore oxygen evolution so to induce an active fluid mixing and the displacement of foulant particles. The present study includes the fabrication of hybrid polymeric films with porous architecture embedding the tetra-ruthenium catalyst as artificial catalase to guarantee the material self-defence against pore occlusion and oxidative damage with aqueous H2O2 as mild chemical effector.La coppia redox acqua-ossigeno, H2O/O2, alimenta la nostra vita aerobica attraverso i processi fondamentali della fotosintesi naturale e della respirazione cellulare. Nonostante il suo ruolo fondamentale, qualsiasi errore in questo meccanismo a quattro elettroni rilascia radicali O2-derivati tossici, inducendo gravi danni ossidativi ai materiali sintetici e biologici esposti. La formazione aerobica di ROS è dovuta alla riduzione dell'ossigeno in vivo, generando l'anione superossido (O2•-), perossido di idrogeno (H2O2) ed il radicale idrossile (HO•). I ROS danno origine ad una veloce ossidazione, senza barriere, a corto raggio e non selettiva, responsabile dello "stress ossidativo", un fattore chiave per la morte cellulare, insufficienza di organi e le malattie dell'invecchiamento. Inoltre lo stress foto-ossidativo è un fattore chiave che limita la produttività di piante, bio-masse e rese alimentari. Meccanismi ROS indotti sono anche letali per la stabilità dei materiali bio-ispirati progettati per fotosintesi artificiale in vitro. La difesa biologica contro i danni cellulari ROS indotti deriva dall'azione combinata di metallo-enzimi "anti-ossidanti", come la superossido dismutasi (SOD) e la catalasi (CAT). Il processo di disintossicazione avviene tramite la dismutazione SOD indotta di O2•- in O2 e H2O2 che viene poi convertita nuovamente da CAT in H2O e O2. In questa tesi verrà presentata la progettazione di una serie di nuovi catalizzatori antiossidanti, basati su differenti centri metallici, che possono derivare dalla progettazione di sinzimi con integrata attività SOD/CAT in grado di imitare entrambi gli enzimi ed eseguire efficientemente una completa rimozione di ROS in condizioni simili a quelle biologiche. L'attività dei sinzimi sarà testata inoltre nei processi di scissione dell'acqua per effettuare sia il processo di ossidazione dell'acqua che la riduzione di protoni in acqua a pH neutro, una caratteristica fondamentale per l’ottenimento fonti energetiche sostenibili dalla acqua.
I risultati ottenuti saranno divisi in quattro capitoli principali:
-Capitolo 2: l’unione di una porfirina policationica di Mn(III), con un sistema dinucleare Mn2(II,II)L2 risulta in un duplice analogo funzionale di superossido dismutasi (SOD) e catalasi (CAT), Mn2L2Pn+, consentendo una disintossicazione a cascata dell'anione superossido e del perossido di idrogeno in H2O e O2. I complessi SOD/CAT artificiali, uniti in un’unica struttura, mostrano un picco delle performance catalitiche in condizioni fisiologiche, con logkcat(O2•-) ≥ 7 e kcat(H2O2)/KM = 1890. Il concetto di doppio-enzima (di-zima) consente una autoprotezione unica, contro la degradazione irreversibile dell'unità porfirinica, (> protezione 75%), indotta rapidamente da H2O2 (200 μM, 20 equivalenti, in soluzione tampone, pH=7.8). Qui viene dimostrato che l'incubazione delle alghe verdi fotosintetiche, Chlamydomonas reinhardtii, con il di-zima sintetico (a concentrazioni fino a 0,1 μM), previene l'accumulo di H2O2 in condizioni di elevata illuminazione, fornendo così un efficiente azione anti-ossidante e foto-protettiva.
-Capitolo 3: sono stati sintetizzati e studiati dei catalizzatori binucleari Cu(II)2L2 per la loro attività SOD/CAT. L'obiettivo di questo studio è stato quello di dimostrare che con una serie di leganti adeguati, è possibile regolare la reattività di un metallo dannoso come il rame, trasformandolo in un sistema anti-ossidante. I complessi binucleari di rame mostrano un’attività SOD con logkcat fino a 7,55 e un'attività CAT con velocità di produzione di O2 fino a 4,4 μM/s. Studi cinetici del processo di dismutazione dell’acqua ossigenata mostrano una evoluzione del catalizzatore durante il turnover catalitico. Nessuna evidenza dell’ossidazione di substrati esterni è stata osservata grazie alla presenza di una funzionalità interna sacrificale.
- Capitolo 4: sono stati isolati dei nuovi complessi Fe(III)L, Fe(III)2L2 e Co2(II)L2. I risultati preliminari indicano che le specie sono in grado di sostenere processi multi-elettronici, ma con scarsa attività nell’eliminazione di ROS. Questi complessi mostrano invece un'attività interessante nel processo di ossidazione dell'acqua. Inoltre le onde anodiche osservate in riduzione sono promettenti nel processo di riduzione catalitica dei protoni eseguito utilizzando direttamente acqua come fonte di protoni.
- Capitolo 5: è stata esplorata l’applicazione nel campo dei materiali funzionali di catalizzatori che sviluppano ossigeno all'interno di membrane porose. Questa nuova strategia stimolo-risposta contro l'incrostazione irreversibile di materiali porosi e superfici si basa sulla progettazione molecolare di pori con pareti catalitiche che esibiscono proprietà autopulenti chemo-meccaniche a pH neutro e in condizioni blande di temperatura e pressione. A questo scopo, l’attività di catalasi di un poliossometallato tetra-rutenio sostituito, è stata sfruttata per lo sviluppo di ossigeno dai pori in modo da indurre una miscelazione attiva del fluido e la rimozione delle particelle sporcanti. Il presente studio prevede la realizzazione di film polimerici ibridi con un’architettura porosa contenenti il catalizzatore di tetra-rutenio come catalasi artificiale per garantire al materiale un meccanismo di auto-difesa contro l’occlusione dei pori e i danni ossidativi, impiegando una soluzione acquosa di H2O2 come stimolo chimico
Andrea Bacová
No full textAndrea Bacová focuses on research and teaching in the field of residential architecture. Her work includes systematic research on residential buildings and their urban context. She actively participates in promoting Slovak architecture and is the author of several publications and exhibitions
Hydrogen Evolution by FeIIIMolecular Electrocatalysts Interconverting between Mono and Di-Nuclear Structures in Aqueous Phase
No full textAnew FeL/Fe2L2 manifold,with HL= 2-({[di(2-pyridyl)methyl]-(methyl)amino}methyl)phenol, was preparedingram scale (> 50%yield) and characterized in solution and solid state. The monomer/dimer interconversion is controlled in aqueous phase, upon varying thepHconditions. The electrocatalytic hy-drogen evolution reaction (HER) occurs through the FeL mono-mer with added trifluoroacetic acid (TFA)and through the Fe2L2 m-oxo dimer in acetate buffer (pH 4.9), with an overpo-tential of about 1Vand faradaic yield up to 75 %. The resulting icat/ip valuesinthe range 15–28are among the highest report-ed for Fe-based electrocatalysts (icat is the catalytic current, whereas ip is the current of an Fe-based redox event)
Viewer-, Author-, and Ownership in the Work of Andrea Zittel
No full textAndrea Zittel invites others to collapse the distinctions between artist, viewer, and collaborator by interacting with her usable works. This thesis explores the process of interacting with Zittel\u27s works, and how it affects viewer-, author- and ownership
The Lettere of Andrea Calmo: authorial artifices and historical reality
No full textopenNonostante l’edizione di Vittorio Rossi del 1888, la raccolta di "ingegnosi cheribizzi" e di "fantastiche fantasie" di Andrea Calmo è ancora avvolta da un certo mistero. L’autore, dissimulando la propria identità dietro alla “maschera” dell’umile pescatore veneziano, è stato in grado di offrire uno spaccato della cultura e della società nella Venezia cinquecentesca.
In particolare, è il quarto libro delle Lettere ad aver suscitato maggiore interesse tra gli studiosi ed i lettori: pubblicato nel 1566, a diversi anni di distanza dai primi tre, questo libro si distingue per il fatto che tutte le epistole sono indirizzate a delle donne immaginarie o realmente esistite.
In questa sede si propone, in primo luogo, uno studio della biografia del Calmo accompagnata da un’analisi del contesto storico-culturale della Venezia cinquecentesca; in secondo luogo, invece, viene proposto un commento di alcune lettere dell’ultimo libro dell’opera calmiana, che cerchi di far luce principalmente sull’aspetto linguistico e contenutistico del testo.Despite Vittorio Rossi's 1888 edition, Andrea Calmo's collection of "ingegnosi cheribizzi" and "fantastiche fantasie" is still shrouded in a certain mystery. The author, dissimulating his own identity behind the "mask" of the humble Venetian fisherman, was able to offer a cross-section of culture and society in sixteenth-century Venice.
In particular, it is the fourth book of the Letters that has aroused greater interest among scholars and readers: published in 1566, several years after the first three, this book stands out for the fact that all the epistles are addressed to women imaginary or actually existed.
Here we propose, first of all, a study of Calmo's biography accompanied by an analysis of the historical-cultural context of sixteenth-century Venice; secondly, however, a commentary on some letters from the last book of Calmo's work is proposed, which seeks to shed light mainly on the linguistic and content aspect of the text
Dynamic Antifouling of Catalytic Pores Armed with Oxygenic Polyoxometalates
No full textA novel stimuli-responsive strategy against the irreversible fouling of porous materials and surfaces is presented herein. This is based on the molecular design of catalytic pore walls that foster a chemo-mechanical, self-cleaning behavior under neutral pH and mild conditions of pressure and temperature. This approach builds on bioinspired remediation mechanisms involving natural catalase enzymes for H2O2 dismutation and endogenous oxygen production. It is thus demonstrated that a very efficient antifouling activity is observed when the material pores are armed with oxygen evolving catalysts that are known to liberate nascent oxygen gas when exposed to H2O2 as chemical trigger. To this aim, the catalase-like behavior of the tetra-ruthenium substituted polyoxometalate (Ru4(SiW10)2), has been exploited for in-pore oxygen evolution so to induce an active fluid mixing and the displacement of foulant particles. The present study includes the fabrication of hybrid polymeric films with porous architecture embedding Ru4(SiW10)2 as artificial catalase to guarantee the material self-defense against pore occlusion and oxidative damage with aqueous H2O2 as mild chemical effector. The self-catalytic “in-pore” remediation is readily applied to various materials/interfaces with porous texture and high surface area with the aim to provide long-lasting functional performance
Trusted Tales: Creating Authenticity in Literary Representations from Ex-Yugoslavia
No full textThis research deals with questions of authority and authenticity and how they are expressed, constructed, and appropriated within the Anglophone book market. It considers the body of literature written about ex-Yugoslavia since the 1990s Balkan conflicts by exiled writers from the region which has entered the international literary canon. Books’ routes from original publishers into English translation are discussed through practices of trust, one of the crucial social devices underpinning their exchange. Within these cross-cultural processes, the role of cultural brokers is crucial. Symbolic and cultural resources are specifically mobilised through their powerful author brands.
By exploring authenticity in the context of book publishing, I further look at how ideas and practices of community are employed and negotiated by writers and those who promote their books. My field is multi-sited and fluid, reflecting how different individual and national positions are enacted and performed through strategies ranging from unconscious dispositions to deliberate intentions. This research thus brings together ideas of the author as an authentic, representative voice together with exile as a position that grants them a new lease of relevancy in the post-socialist context.
Although ex-Yugoslav books occupy a ‘high end’ niche of the UK market, constrained by commercial as well as political, cultural, and institutional forces, in public discourse ideas of the ‘free market’ and ‘free speech’ are mobilised to produce various types of modernisation narratives. The (post)socialist production of literature is perceived as having to ‘evolve’ into a capitalist model: this would allow not only healthy competition and consumer choice but guarantee an individual writer ‘free speech’ as a basic human right. Therefore, the most general question this research raises is what kind of foreign literature gets translated into English, under what socio-cultural conditions and which politics of representation it serves within the project of world literature
Ms. Courtney Chartier, RWWL AUC, August 2011
No full textThis video is a conversation with Ms. Courtney Chartier. Ms. Chartier talks about her work on the "New Georgia Encyclopedia" and "Online Voter Education Project." Andrea Jackson, AUC Woodruff Library, is the interviewer
Tribute to Andrea Infuso
No full textThis special issue of Eurosurveillance is dedicated to the memory of Andrea Infuso, a dear and respected colleague and friend, who died suddenly on 20 September 2005 at the age of 44.
Andrea was actively involved in the preparation of this special issue on vaccination and tuberculosis. As EuroTB coordinator since 2000, his knowledge of and contacts with all European experts involved in tuberculosis surveillance in Europe were very valuable in conceiving this thematic issue. The Euroroundup published in this issue, European survey of BCG vaccination policies and surveillance in children, 2005, written by Andrea as first author, is a posthumous publication.</jats:p
Search-based multi-vulnerability testing of XML injections in web applications (vol 24, pg 3696, 2019): Search-based multi-vulnerability testing of XML injections in web applications (Empirical Software Engineering, (2019), 10.1007/s10664-019-09707-8)
No full textThe article Search-based multi-vulnerability testing of XML injections in web applications, written by Sadeeq Jan, Annibale Panichella, Andrea Arcuri, and Lionel Briand, was originally published electronically on the publisher’s internet portal (currently SpringerLink) on May 2019 without open access. With the author(s)’ decision to opt for Open Choice the copyright of the article changed on June 2019 toSoftware Engineerin
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