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Urease is a nickel-dependent enzyme that catalyzes hydrolysis of urea in the last step of organic nitrogen mineralization. Its active site contains a dinuclear center for Ni(II) ions that must be inserted into the apo-enzyme through the action of four accessory proteins (UreD, UreE, UreF, UreG) leading to activation of urease. UreE, acting as a metallo-chaperone, delivers Ni(II) to the preformed complex of apo-urease-UreDFG and has the capability to enhance the GTPase activity of UreG. This study, focused on characterization of UreE from Sporosarcina pasteurii (SpUreE), represents a piece of information on the structure/mobility-function relationships that control nickel binding by SpUreE and its interaction with SpUreG. A calorimetric analysis revealed the occurrence of a binding event between these proteins with positive cooperativity and a stoichiometry consistent with the formation of the (UreE)2-(UreG)2 hetero-oligomer complex. Chemical Shift Perturbations induced by the protein-protein interaction were analyzed using high-resolution NMR spectroscopy, which allowed to characterize the molecular details of the protein surface of SpUreE involved in the complex formation with SpUreG. Moreover, backbone dynamic properties of SpUreE, determined using 15N relaxation analysis, revealed a general mobility in the nanoseconds time-scale, with the fastest motions observed at the C-termini. The latter analysis made it possible for the first time to characterize of the C-terminal portions, known to contain key residues for metal ion binding, that were not observed in the crystal structure of UreE because of disorder. The residues belonging to this portion of SpUreE feature large CSPs upon addition of SpUreG, showing that their chemical environment is directly affected by protein-protein interaction. Metal ion selectivity and affinity of SpUreE for cognate Ni(II) and non cognate Zn(II) metal ions were determined, and the ability of the protein to select Ni(II) over Zn(II), in consistency with the proposed role in Ni(II) cations transport, was established.

In this thesis, the synthesis of nano-micro particles of crystalline inorganic materials and four different applications involving their use, are presented . Inorganic particles have been synthesized following two main criteria: i) the particle’s dimensions, specific surface area and crystalline phase of the product have been optimized for the practical application; ii) both the synthesis and application should be based on a simple procedure, environmental low impact, economical affordability. In particular, Titanium dioxide nanoparticles have been synthesized by sol-gel hydrolysis of Titanium(IV) isopropoxide in an isopropyl alcohol/water solution. The isopropyl alcohol contained in the solvent mixture act as a capping agent stabilizing the forming nanometric particles, and play also a role in the suspension stability. Synthesized Titanium dioxide reveals good photocatalytic properties directly as synthesized, without needing further thermal treatment. Photoactive Titanium dioxide have been used for NOx pollutants abatement on waste gases produced by a working plant and as self-cleaning coating on photovoltaic Silicon panels, showing good results. Crystalline calcium phosphate nano and micro particles, in particular Hydroxyapatite, Brushite, Monetite and Mg-doped β-Tricalcium phosphate have been synthesized. Two applications of the synthesized Calcium phosphates are reported, both based on the drug delivery concept. Hydroxyapatite nanocrystals were used to adsorbe and retain on their surface anticancer drugs based on a Platinum complex, and release them in response to a pH variation. Phytotherapics active elements have been stabilized by physisorption on Calcium phosphates particles surface. The administration of the obtained suspensions shows good results in terms of plant’s healing, using a lower amount of phytotherapic elements compared to the commercial products. / In questa tesi sono riportate sintesi e caratterizzazione di nano-micro particelle di materiale cristallino inorganico, e quattro loro applicazioni. Le particelle inorganiche sono state preparate seguendo due criteri principali: i) le proprietà chimico-fisiche delle particelle devono essere ottimizzate in funzione dell’applicazione; ii) sintesi e applicazione devono essere basate su procedure semplici, con basso impatto ambientale ed economicamente sostenibili. In particolare, nano particelle di Titanio biossido sono state sintetizzate tramite reazione di idrolisi di Titanio(IV) isopropossido in una soluzione di acqua a alcol isopropilico. L’alcol isopropilico presente nella miscela di solventi agisce da agente cappante stabilizzando le nanoparticelle in formazione e dimostra un ruolo nella stabilità della sospensione. Il Titanio biossido prodotto ha rivelato buone proprietà foto catalitiche senza bisogno di ulteriori trattamenti termici. Il Titanio biossido foto attivo è stato applicato con buoni risultati nell’abbattimento di NOx dalle emissioni di uno stabilimento e come strato autopulente su dei pannelli fotovoltaici. Sono state sintetizzate nano e micro particelle di calcio fosfati cristallini, nello specifico Idrossiapatite, Brushite, Monetite and β-Tricalcio fosfato Mg-sostituito. Ne sono riportate due applicazioni, entrambe basate sul concetto di drug delivery. Nanocristalli di Idrossiapatite sono stati utilizzati per adsorbire e ritenere sulla loro superficie farmaci chemioterapici basati su complessi di Platino, e successivamente rilasciare il farmaco in risposta ad una variazione di pH. Alcuni principi attivi fitoterapici sono stai stabilizzati tramite fisisorbimento sulla superficie di particelle di Calcio fosfati in sospensione. La loro applicazione ha dimostrato buoni risultati curativi sulle piante, utilizzando quantitativi di principio attivo molto ridotti rispetto ai prodotti commerciali.

In thesis work it has been given an overview of the most recent advances in the synthesis, characterization and bio-medical application of luminescent Gold nanospecies. It has been shown that the combination of photoactuators and nanostructures results in an apparent reduction of dyes PI QYs, due to the nanomaterials absorbance contribution, also in absence of actual interactions between the two components. It has been proposed a simple approach to take into consideration this contribution and to perform quantitative measurements of dyes PI efficiencies variations in presence of nanoparticles. The PI QY reduction has been found to be qualitatively proportional to the magnitude of the interaction between the dye and the particles measured by NMR. It has been shown that strong interaction between the two components result in significant decreases of the dye PI QY. The photoisomerization effectively determines a change in the repartition of the AB derivative between particle monolayer and solution. This confirms that photoisomerization reaction can probably be exploited for light triggered drug release. These results provided valuable tools and methodologies which improved the state of the art in the quantitative study of light triggered processes in nanoparticles based systems. For the first time it has been proven that GNPs luminescence can be switched on and off thanks to the photoisomerization of an azobenzene derivative covalently bound on the Gold surface. This has been proven to happen thanks to an efficient energy transfer between the trans AB derivative and the GNPs which leads to a sensitized NIR emission whose intensity can be tuned by photoisomerization. These unprecedented results are promising for the development of Gold based light responsive nanoparticles for theranostics. Finally, starting from Au25(Cys)18, it has been successfully developed a complex probe for luminescence based imaging composed by NIR emitting GNCs encapsulated inside mesoporous PEGylated silica NPs.

The PhD thesis herein presented deal with the synthesis, characterization and catalytic application of new ruthenium transition metal complexes which exhibit unprecedented combination of ligands: cyclopentadienones and N-heterocyclic carbenes (NHC). In the first year of the PhD work it was developed a straightforward and efficient synthetic route to novel Ru N-heterocyclic carbenes (NHC) complexes by transmetallation of non-bulky imidazolylidene silver complexes to ruthenium dicarbonyl tetraarylcyclopentadienone. The same procedure with sterically demanding NHC resulted in the formation of unprecedented heterobimetallic Ru-Ag(NHC) complexes. During the second year six months (from March to September 2014) have been spent at the UCD School of Chemistry and Chemical Biology, University College of Dublin, under the supervision of Professor Martin Albrecht investigating the steric and electronic tunability of the catalyst precursors by replacing imidazolylidenes with triazolylidenes. Triazolylidenes are stronger donors than imidazolylidenes, and hence they further activate the ruthenium(0) oxidation state in dicarbonyl tetraarylcyclopentadienone Ru (NHC) complexes, which resulted to be beneficial in catalytic applications. During the second and third year the novel classes of ruthenium complexes were successfully employed as catalyst precursors in the transfer hydrogenation of ketones and aldehydes using iPrOH as hydrogen source. Fine tuning of several molecular parameters and reaction conditions allowed to improve catalytic performances. Furthermore, the catalysts were employed for the oxidation of alcohol with promising results. Heterogenization of the catalyst on polypropylene imine dendrimers has been also developed, moreover ionic ruthenium complexes have been also exploited as potential catalyst in ionic liquids. Greener synthetic conditions have been found both for the synthesis of ruthenium complexes under microwave irradiation and for the acid catalysed transformation of the bio-based bis-hydroxymethylfuran. Preliminary electrochemical measurements have been carried out on a triazolylidene Ru(0) complex. Its redox behaviour could be exploited in the development of electrocatalysis.

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Con questo lavoro di tesi si è cercato da un lato di dare un contributo al settore dei sensori chimici, caratterizzando e sviluppando diversi sistemi che presentano promettenti proprietà per l’utilizzo nella realizzazione di sensori luminescenti, e dall’altro di studiare sistemi di nanoparticelle di oro per identificarne e caratterizzarne i processi che portano all’interazione con un’unità fluorescente di riferimento, il pirene. Quest’ultima parte della tesi, sviluppata nel capitolo 4, sebbene possa apparire “slegata” dall’ambito della sensoristica, in realtà non lo è in quanto il lavoro di ricerca svolto rappresenta una buona base di partenza per lo sviluppo di sistemi di nanoparticelle metalliche con un possibile impiego in campo biomedico e diagnostico. Tutte le specie studiate, seppur molto diverse tra loro, posseggono quindi buone caratteristiche di luminescenza ed interessanti capacità di riconoscimento, più o meno selettivo, di specie in soluzione o allo stato gassoso. L’approccio generale che è stato adottato comporta una iniziale caratterizzazione in soluzione ed una susseguente ottimizzazione del sistema mirata a passare al fissaggio su supporti solidi in vista di possibili applicazioni pratiche. A tal proposito, nel capitolo 3 è stato possibile ottenere un monostrato organico costituito da un recettore (un cavitando), dotato di una parte fluorescente le cui proprietà di luminescenza sono sensibili alla presenza di una funzione chimica che caratterizza una classe di analiti, gli alcoli. E’ interessante sottolineare come lo stesso sistema in soluzione si comporti in maniera sostanzialmente differente, mostrando una capacità di segnalare l’analita molto meno efficiente, anche in funzione di una diversa orientazione della parte fluorescente. All’interfaccia solido-gas invece, l’orientamento del fluoroforo gioca un ruolo chiave nel processo di riconoscimento, e ottimizzando ulteriormente il setup sperimentale e la composizione dello strato, sarà possibile arrivare a segnalare quantità di analita sempre più basse. Nel capitolo 5 invece, è stato preso in esame un sistema le cui potenzialità, per un utilizzo come sonda fluorescente nel campo delle superfici di silicio, sembra promettere molto bene. A tal proposito sono stati discussi anche i risultati del lavoro che ha fornito l’idea per la concezione di questo sistema che, a breve, verrà implementato a sua volta su superficie solida. In conclusione, le ricerche descritte in questa tesi hanno quindi contribuito allo sviluppo di nuovi chemosensori, cercando di migliorare sia le proprietà fotofisiche dell’unità attiva, sia quelle dell’unità recettrice, sia, infine, l’efficienza del processo di traduzione del segnale. I risultati ottenuti hanno inoltre permesso di realizzare alcuni prototipi di dispositivi sensoriali aventi caratteristiche molto promettenti e di ottenere informazioni utili per la progettazione di nuovi dispositivi (ora in fase di sviluppo nei laboratori di ricerca) sempre più efficienti, rispondendo in tal modo alle aspettative con cui questo lavoro di dottorato era stato intrapreso.

No description available.

The introduction of hydroxyl groups into ligands is able to transfer high hydrophilic features to the related metal systems. The atom-economy synthetic procedure adopted which consists in the one-step Cyclopentene-oxide ring opening, quantitatitatively affords stereoselective formation of the multi-hydroxyl rac-1,2,4- C5H2[CH(CH2)3CHOH]3 Cpººº ligand1. Rh complexation of Cpººº gives rise to a novel class of water-soluble complexes (L,L)RhCpººº (LL=NBD 1, COD 2, CH2CH2 3, CO 4) (Scheme 1) characterized by their spectroscopic features (ESI-MS, IR, 2D NMR, n.O.e.). The X-ray diffraction studies of 1a reveal the occurrence of one couple of enantiomeric pairs in the crystal structure, whilst the crystal packing shows an interesting self-organization in chains of dimeric units of 1a, promoted by strong intermolecular hydroxyl H-bonding. This effect has been exploited by performing VT NMR experiments in different solvents (CDCl3, Py, DMSO). Unpredictably, in the absence of chiral tag, 1 exhibits solvent-dependent chiroptical properties (CD, αD^ 25), which are correlated to UV transitions and DFT calculations. The intra/inter molecular H-binding is crucial in driving the equilibrium between the observed atropisomers 1a and 1b, by varying the planar chirality on the two π-complexes.