53 research outputs found
Supramolecular Binding with Lectins: A New Route for Non-Covalent Functionalization of Polysaccharide Matrices
No full textThe chemical functionalization of polysaccharides to obtain functional materials has been of great interest in the last decades. This traditional synthetic approach has drawbacks, such as changing the crystallinity of the material or altering its morphology or texture. These modifications are crucial when a biogenic matrix is exploited for its hierarchical structure. In this work, the use of lectins and carbohydrate-binding proteins as supramolecular linkers for polysaccharide functionalization is proposed. As proof of concept, a deproteinized squid pen, a hierarchically-organized β-chitin matrix, was functionalized using a dye (FITC) labeled lectin; the lectin used was the wheat germ agglutinin (WGA). It has been observed that the binding of this functionalized protein homogenously introduces a new property (fluorescence) into the β-chitin matrix without altering its crystallographic and hierarchical structure. The supramolecular functionalization of polysaccharides with protein/lectin molecules opens up new routes for the chemical modification of polysaccharides. This novel approach can be of interest in various scientific fields, overcoming the synthetic limits that have hitherto hindered the technological exploitation of polysaccharides-based materials
Incorporation of Molecular Nanoparticles Inside Proteins: The Trojan Horse Approach in Theranostics
No full textCONSPECTUS: Molecular nanoparticles, MNPs, characterized by well-defined chemical formulas, structures, and sizes can interact with a variety of proteins. Fullerenes, carboranes, and gold nanoclusters well represent the diversity of MNPs properties available in nanoscience. They can have diameters smaller than 1.5 nm, be hydrophilic or hydrophobic, and can use a paraphernalia of means to establish local and global interactions with the amino acidic residues of proteins. Proteins, endowed as they are with an assortment of pockets, crevices, and gaps are natural supramolecular hosts to incorporate/hide/transport MNPs directly in water with a facile and "green" approach.This Account identifies and discusses the rules that govern the interactions and binding between MNPs and proteins. Fullerenes are composed solely by carbon atoms arranged to form hollow polyhedra. Hydrophobic interactions occur between aliphatic residues and the fullerene surface. The amino acids most effectively interacting with fullerenes are aromatic residues that establish p-p stacking interactions with the cage. Amphiphilic and charged residues produce also cation-p, anion-p, and surfactant-like interactions with the cages.Carboranes are composed of boron, carbon, and hydrogen atoms, also arranged to form cages. They are hydrophobic with unusual properties originating from the presence of boron atoms. Hydride-like hydrogens bound to the boron atoms govern carborane chemistry. These negatively charged hydrogens do not participate in classic hydrogen bonding with water and promote hydrophobic interactions with proteins. On the contrary, the electronegativity of these hydrogens drives the formation of unconventional dihydrogen bonds with the acidic hydrogen atoms of positively charged amino acid. Carboranes also establish C-H center dot center dot center dot p and B-H center dot center dot center dot p interactions with aromatic residues.Gold nanoclusters, AuNCs, are synthesizable with atomically precise stoichiometry. Amino acid residues with sulfur atoms or with nitrogen-containing heterocycles are the strongest Au binders. The proteins can act as supramolecular hosts but also as templates for the synthesis of AuNCs directly inside the protein core. Of the pristine amino acids, tryptophan, tyrosine, phenylalanine, and aspartic acid are the most efficient reducing groups. In a peptide sequence, the best Au-reducing moieties are obtained by nitrogencontaining residue such as glutamine, asparagine, arginine, and lysine. The investigation of the interactions between AuNCs and proteins therefore adds further complexity with respect to that of fullerenes and carboranes. The selection of the host proteins should consider that they will have to contain active sites for metal ion accumulation and ion reduction where AuNC can form and stabilize. This Account further discusses the hybridization of MNPs with proteins in view of creating innovative multifunctional theranostic platforms where the role of proteins is akin to that of "Trojan Horses" since they can (i) hide the MNPs, (ii) control their cellular uptake, (iii) drive their crossing of physiological barriers, and (iv) ultimately govern their biological fate
Operations and Thermodynamics of an Artificial Rotary Molecular Motor in Solution
No full textA general framework is provided that makes possible the estimation of time-dependent properties of a stochastic system moving far from equilibrium. The process is investigated and discussed in general terms of nonequilibrium thermodynamics. The approach is simple and can be exploited to gain insight into the dynamics of any molecular-level machine. As a case study, the dynamics of an artificial molecular rotary motor, similar to the inversion of a helix, which drives the motor from a metastable state to equilibrium, are examined. The energy path that the motor walks was obtained from the results of atomistic calculations. The motor undergoes unidirectional rotation and its entropy, internal energy, free energy, and net exerted force are given as a function of time, starting from the solution of Smoluchowski’s equation. The rather low value of the organization index, that is, the ratio of the work done by the particle against friction during the unidirectional motion per available free energy, reveals that the motion is mainly subject to randomness, and the amount of energy converted to heat due to the directional motion is very small
C60bioconjugation with proteins: Towards a palette of carriers for all pH ranges
No full textThe high hydrophobicity of fullerenes and the resulting formation of aggregates in aqueous solutions hamper the possibility of their exploitation in many technological applications. Noncovalent bioconjugation of fullerenes with proteins is an emerging approach for their dispersion in aqueous media. Contrary to covalent functionalization, bioconjugation preserves the physicochemical properties of the carbon nanostructure. The unique photophysical and photochemical properties of fullerenes are then fully accessible for applications in nanomedicine, sensoristic, biocatalysis and materials science fields. However, proteins are not universal carriers. Their stability depends on the biological conditions for which they have evolved. Here we present two model systems based on pepsin and trypsin. These proteins have opposite net charge at physiological pH. They recognize and disperse C60in water. UV-Vis spectroscopy, zeta-potential and atomic force microscopy analysis demonstrates that the hybrids are well dispersed and stable in a wide range of pH's and ionic strengths. A previously validated modelling approach identifies the protein-binding pocket involved in the interaction with C60. Computational predictions, combined with experimental investigations, provide powerful tools to design tailor-made C60@proteins bioconjugates for specific applications
Pseudopeptide-Based Hydrogels Trapping Methylene Blue and Eosin Y
No full textWe present herein the preparation of four different hydrogels based on the pseudopeptide gelator Fmoc-l-Phe-d-Oxd-OH (Fmoc=fluorenylmethyloxycarbonyl), either by changing the gelator concentration or adding graphene oxide (GO) to the water solution. The hydrogels have been analysed by rheological studies that demonstrated that pure hydrogels are slightly stronger compared to GO-loaded hydrogels. Then the hydrogels efficiency to trap the cationic methylene blue (MB) and anionic eosin Y (EY) dyes has been analyzed. MB is efficiently trapped by both the pure hydrogel and the GO-loaded hydrogel through π–π interactions and electrostatic interactions. In contrast, the removal of the anionic EY is achieved in less satisfactory yields, due to the unfavourable electrostatic interactions between the dye, the gelator and GO
Acceleration of oxidation promoted by laccase irradiation with red light
No full textIrradiation with red light is able to improve yields and shorten the reaction time in enzymatic reactions. A commercially available laccase from Trametes versicolor, used in conjunction with a catalytic amount of TEMPO (20 mol%), was irradiated under red light (630 nm) for the clean oxidation of benzylic alcohols and amines in a faster reaction compared to the one conducted in the dark, affording the desired product in excellent yields (up to 99%) using air as the terminal oxidant. The observed acceleration is due to the strongest oxidation ability of laccase, in its excited state, towards TEMPO
Luminescent gold nanoclusters as biocompatible probes for optical imaging and theranostics
No full textOptical bioimaging is a powerful tool for investigating living organisms in real time and space, both in-vivo and in-vitro. As an advantage, luminescence based techniques are poorly invasive and highly sensitive when compared to other diagnostic approaches. In order to exploit these attractive features, the search of highly biocompatible contrast agents with spectral controllable signatures and good photostability is needed. Gold nanoclusters (GNCs) based probes promise to merge all these characteristics, being their emission tunable from the visible (VIS) to the near infrared region (NIR), a spectral window ideal for photo-activation and detection in-vivo. In this review article, examples of the most recent applications of GNCs to in-vitro and in-vivo imaging are discussed, also considering the development and the use of multimodal and multifunctional probes, able to combine diagnostic and therapeutic (theranostic) actions. Brightness, photostability and toxicity of GNCs in biological systems are critically analyzed. For a complete overview, the origin of the optical properties of GNCs, as well as their preparation, is briefly discussed
Morphological changes of calcite single crystals induced by graphene–biomolecule adducts
No full textCalcite has the capability to interact with a wide variety of molecules. This usually induces changes in shape and morphology of crystals. Here, this process was investigated using sheets of graphene–biomolecule adducts. They were prepared and made dispersible in water through the exfoliation of graphite by tip sonication in the presence tryptophan or N-acetyl-D-glucosamine. The crystallization of calcium carbonate in the presence of these additives was obtained by the vapor diffusion method and only calcite formed. The analysis of the microscopic observations showed that the graphene–biomolecule adducts affected shape and morphology of rhombohedral 10.4 faced calcite crystals, due to their stabilization of additional hk.0 faces. The only presence of the biomolecule affected minimally shape and morphology of calcite crystals, highlighting the key role of the graphene sheets as 2D support for the adsorption of the biomolecules
«Giochi di pazienza». Il ms. London, British Library, King’s 322. Un codice acquaviviano?
No full textL’inedito ed elegante codice miniato London, British Library, King’s 322, è collegato, nel catalogo della Biblioteca nazionale del Regno Unito, in maniera dubitativa alla committenza del principe guerriero umanista e mecenate Andrea Matteo III Acquaviva d’Aragona, di cui è noto l’interesse per l’arte, la musica ma soprattutto le lettere, e che fu committente e collezionista di splendidi manoscritti miniati per la sua biblioteca personale, greca e latina.
Sulla base dell’accuratissimo esame delle componenti materiali, grafiche e perigrafiche del pregevole manufatto, operato da Marco Antonio Siciliani, è stata esclusa la committenza dell’Acquaviva e formulata una proposta di datazione cronica che copre l’arco di tempo compreso tra gli anni Trenta e gli anni Sessanta del XV secolo e topica, che individua Milano, come area di allestimento dello stesso. Ipotesi che si accorda con la proposta di George f. Warner e Julius P. Gilson, che hanno riconosciuto nelle miniature del codice londinese l’opera del Maestro delle Vitae imperatorum, il miniatore preferito di Maria Filippo Visconti e della sua corte o di un membro della sua cerchia.
Nel contributo prospetto un’altra ipotesi attributiva, evidenziando i possibili ‘legami’ del pregevole manoscritto miniato con Giosia Acquaviva, duca d’Atri e signore di Teramo, nonno del principe umanista Andrea Matteo III.
Gioia intrattenne stretti rapporti negli anni Trenta del XV secolo con il duca di Milano Filippo Maria Visconti e la sua corte, testimoniati tra l’altro dal prezioso carteggio pubblicato da Francesco Savini (1846-1940).
In anni di grande turbolenza politico-militare, durante i quali famiglie d’antico lignaggio o di recente fortuna mercantile cercavano di imporre la loro signoria sulle varie autonomie cittadine della regione, approfittando delle contese dinastiche seguite alla morte di Carlo III di Durazzo e della concorrenziale convergenza di interessi da parte dello Stato della Chiesa e del ducato di Milano sui confini settentrionali del regno di Napoli, Giosia Acquaviva divenuto fautore degli Aragonesi nella lotta tra Renato d’Angiò ed Alfonso d’Aragona, nel 1435 venne coinvolto nella disfatta inflitta dai Genovesi alla flotta aragonese nelle acque di Ponza. Tradotto con gli altri prigionieri a Milano, fu consegnato nelle mani di Filippo Maria Visconti. Giosia nel periodo di «prigionia onorevole» che trascorse presso la corte viscontea rinsaldò i rapporti con il duca di Milano e poté conoscere personaggi di primo piano del suo entourage.
Liberato contemporaneamente al re Alfonso nello scorcio del medesimo anno, tornato in Abruzzo, come fautore degli Aragonesi nel febbraio 1436 ebbe danaro da Alfonso per molestare Iacopo Caldora, di cui era parente, mentre dal duca di Milano Filippo Maria Visconti nel 1437 veniva nominato Luogotenente generale nell’Abruzzo ultra e citra e nella marca. Dal diploma ducale si evince l’alta stima del Visconti per Giosia, del quale viene esaltata «l’industria, la previdenza, la magnanimità, la prudenza e gravità in ogni affare, unite alla lealtà, benevolenza ed affetto verso la sua persona». Il duca di Milano affida così all’Acquaviva «ogni suo negozio, per quanto arduo e importante, certo che egli lo condurrà a termine con sagacia e diligenza, come suo negozio personale»33, in primis, come si evince dal carteggio pubblicato da Savini, quello di intraprendere una spedizione militare contro Francesco Sforza che stava estendendo il suo potere nelle Marche.
Vorrei infine ricordare l’attribuzione a Giosia, da parte di Francesca Manzari, della committenza dello smembrato e disperso Antifonario Acquaviva, di cui lei ha studiato alcuni fogli e ritagli conservati in varie collezioni italiane ed estere; forse non è privo di interesse evidenziare che la studiosa abbia visto nell’apparato miniaturistico l’influenza della cultura lombarda attraverso la mediazione della cultura veneta o bolognese. Su di essi, inoltre, è presente il blasone più antico degli Acquaviva, il leone rampante, al centro del margine inferiore o laterale o nell’occhiello dell’iniziale decorata, del tutto identico a quello che ha impressionato in negativo il verso della prima carta del codice londinese King’s 322
Carbon-Based Hybrid Nanostructures for Advanced Functional Materials
No full textAll the carbon based nanomaterials (CNMs) are highly hydrophobic, which make them unsuitable for most of the applications in water and organic solvents. Aggregation phenomena significantly reduce the high performances displayed by the single nanostructure. Two main strategies allow to overcome this bottleneck: the chemical functionalization with hydrophilic functional groups or the non-covalent interaction between CNMs and amphiphilic molecules.
The aim of this thesis has been to produce different carbon-based hybrid nanostructures to preserve the peculiar properties of CNMs and use them for advanced application in nanomedical and technological fields.
In the first project, the potential application of fullerene (C60) as sensitizer for photodynamic therapy was explored. Monodispersity of fullerenes is the key feature for its potential application in this field. Noncovalent approach was used to disperse C60 in water, taking advantage from the
surfactant-like properties of the proteins. C60@lyszoyme hybrid was used as model system to study the stability of fullerene in physiological conditions and to assess its ability to produce reactive oxygen species upon irradiations.
The second subject of my research concerned the study of interactions between fluorescent nanodiamonds (FNDs) and plasma proteins. FNDs show potential applications as probe for bioimaging but their tendency to aggregate in physiological environments is the main limit for their application. In this study, a procedure to keep monodispersed FNDs in relevant biological fluids was optimized and the composition of FNDs protein corona was extensively characterized.
The third project was addressed to the manufacturing of graphene based calcite nanocomposite. Both covalent (graphene oxide) and non-covalent (graphene/biomolecules adducts) approaches were used to disperse graphene in water. Following a biological inspired synthetic procedure, it
was possible to incorporate the 2D materials within a 3D crystal lattice, producing a nanocomposite possessing several new properties
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