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1.
Faraday Discuss ; 2020 Dec 10.
Artigo em Inglês | MEDLINE | ID: mdl-33300505

RESUMO

Commercial hollow fiber filters for micro- and ultrafiltration are based on size exclusion and do not allow the removal of small molecules such as antibiotics. Here, we demonstrate that a graphene oxide (GO) layer can be firmly immobilized either inside or outside polyethersulfone-polyvinylpyrrolidone hollow fiber (Versatile PES®, hereafter PES) modules and that the resulting core-shell fibers inherits the microfiltration ability of the pristine PES fibers and the adsorption selectivity of GO. GO nanosheets were deposited on the fiber surface by filtration of a GO suspension through a PES cartridge (cut-off 0.1-0.2 µm), then fixed by thermal annealing at 80 °C, rendering the GO coating stably fixed and unsoluble. The filtration cut-off, retention selectivity and efficiency of the resulting inner and outer modified hollow fibers (HF-GO) were tested by performing filtration on water and bovine plasma spiked with bovine serum albumin (BSA, 66 kDa, ≈15 nm size), monodisperse polystyrene nanoparticles (52 nm and 303 nm sizes), with two quinolonic antibiotics (ciprofloxacin and ofloxacin) and rhodamine B (RhB). These tests showed that the microfiltration capability of PES was retained by HF-GO, and in addition the GO coating can capture the molecular contaminants while letting through BSA and smaller polystyrene nanoparticles. Combined XRD, molecular modelling and adsorption experiments show that the separation mechanism does not rely only on physical size exclusion, but involves intercalation of solute molecules between the GO layers.

2.
Front Bioeng Biotechnol ; 8: 560349, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33251194

RESUMO

Bionic composites are an emerging class of materials produced exploiting living organisms as reactors to include synthetic functional materials in their native and highly performing structures. In this work, single wall carboxylated carbon nanotubes (SWCNT-COOH) were incorporated within the roots of living plants of Arabidopsis thaliana. This biogenic synthetic route produced a bionic composite material made of root components and SWCNT-COOH. The synthesis was possible exploiting the transport processes existing in the plant roots. Scanning electrochemical microscopy (SECM) measurements showed that SWCNT-COOH entered the vascular bundles of A. thaliana roots localizing within xylem vessels. SWCNT-COOH preserved their electrical properties when embedded inside the root matrix, both at a microscopic level and a macroscopic level, and did not significantly affect the mechanical properties of A. thaliana roots.

3.
Chem Commun (Camb) ; 56(79): 11835-11838, 2020 Oct 11.
Artigo em Inglês | MEDLINE | ID: mdl-33021268

RESUMO

The design of molecular rotors that can rotate at ultrahigh speeds is important for the development of artificial molecular machines. Based on theoretical calculations, we demonstrate that two kinds of carbon nano-rings, i.e. [n]cycloparaphenylenes ([n]CPP) and cyclo[18]carbon (C18), can form an ultrafast ring-in-ring nano-rotor through π-π interaction. As a high-symmetry and low-barrier rotator, the rotational frequency of C18 in [11]CPP is close to the THz regime. At low temperatures, the motion of the [11]CPP:C18 system is purely rotational. As temperature increases, precession movements start to be observed and the motion resembles the behaviour of a gyroscope. The [11]CPP:C18 rotor can serve as a building block for bottom-up construction of more complex molecular machines.

4.
Nat Nanotechnol ; 15(7): 512-513, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-32533115
5.
Chemistry ; 26(46): 10427-10432, 2020 Aug 17.
Artigo em Inglês | MEDLINE | ID: mdl-32346922

RESUMO

The site-selective allylative and allenylative dearomatization of indoles with alcohols was performed under carbocatalytic regime in the presence of graphene oxide (GO, 10 wt % loading) as the promoter. Metal-free conditions, absence of stoichiometric additive, environmentally friendly conditions (H2 O/CH3 CN, 55 °C, 6 h), broad substrate scope (33 examples, yield up to 92 %) and excellent site- and stereoselectivity characterize the present methodology. Moreover, a covalent activation model exerted by GO functionalities was corroborated by spectroscopic, experimental and computational evidences. Recovering and regeneration of the GO catalyst through simple acidic treatment was also documented.

6.
J Photochem Photobiol B ; 206: 111852, 2020 Mar 13.
Artigo em Inglês | MEDLINE | ID: mdl-32199235

RESUMO

Photodynamic therapy (PDT) is considered a very promising therapeutic modality for antimicrobial therapy. Although several studies have demonstrated that Gram-positive bacteria are very sensitive to PDT, Gram-negative bacteria are more resistant to photodynamic action. This difference is due to a different cell wall structure. Gram-negative bacteria have an outer cell membrane containing lipopolysaccharides (LPS) that hinder the binding of photosensitizer molecules, protecting the bacterial cells from chemical attacks. Combination of the lipopolysaccharides-binding activity of Concanavalin A (ConA) with the photodynamic properties of Rose Bengal (RB) holds the potential of an innovative protein platform for targeted photodynamic therapy against Gram-negative bacteria. A ConA-RB bioconjugate was synthesized and characterized. Approximately 2.4 RB molecules were conjugated per ConA monomer. The conjugation of RB to ConA determines a decrease of the singlet oxygen generation and an increase of superoxide and peroxide production. The photokilling efficacy of the ConA-RB bioconjugate was demonstrated in a planktonic culture of E. coli. Irradiation with white light from a LED lamp produced a dose-dependent photokilling of bacteria. ConA-RB conjugates exhibited a consistent improvement over RB (up to 117-fold). The improved uptake of the photosensitizer explains the enhanced PDT effect accompanying increased membrane damages induced by the ConA-RB conjugate. The approach can be readily generalized (i) using different photo/sonosensitizers, (ii) to target other pathogens characterized by cell membranes containing lipopolysaccharides (LPS).

7.
J Colloid Interface Sci ; 571: 174-184, 2020 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-32199270

RESUMO

The preferred spatial orientation of single-wall carbon nanotubes (SWCNTs) in their interaction with enzymes determines their behavior either as nano-supports or as inhibitors. α -chymotrypsin (α-CT) is considered a serine protease model for studying nanomaterial/proteases interactions. The interaction of α-CT with pristine single-wall carbon nanotubes is still unknown. Here α-CT/SWCNT hybrids are synthesized and characterized. Spectroscopic, microscopic and kinetic measurements, coupled to molecular dynamics simulations, provide a detailed description of the interaction between α-CT and SWCNTs. The SWCNT binding pocket was unambiguously identified. A perfect match is observed with the crevice structure of the α-CT substrate binding pocket. The activity of α-CT, upon SWCNT binding, is dramatically reduced, as expected by the interaction of the SWCNT in the active site of the protein. π-π stacking between aromatic residues and the conjugated surface of SWCNT governs α-CT/SWCNT interactions. An important role in the bonding appears also for purely hydrophobic residues and with residues able to establish surfactant-like interactions. The secondary structure of α-CT and the catalytic triad structure are not perturbed by the complex formation, on the contrary the volume of the substrate binding pocket is strongly reduced by SWCNT binding because SWCNT occupies the α-CT substrate binding site, clogging the active site.

8.
J Chem Theory Comput ; 16(4): 2172-2180, 2020 Apr 14.
Artigo em Inglês | MEDLINE | ID: mdl-32091885

RESUMO

The prototype Diels-Alder (DA) reaction between butadiene and ethene (system 1) and the DA reaction involving 1-methoxy-butadiene and cyano-ethylene (system 2) are investigated with an explicit-time-dependent Density Functional Theory approach. Bond orders and atomic net charges obtained in the dynamics at the transition state geometry and along the reaction coordinate toward reactants are used to provide a picture of the process in terms of VB/Lewis resonance structures that contribute to a resonance hybrid. The entire dynamics can be divided into different domains (reactant-like, product-like, and transition state domains) where different Lewis resonance structures contribute with different weights. The relative importance of these three domains varies along the reaction coordinate. In addition to the usual reactant-like and product-like covalent Lewis structures, ionic Lewis structures have non-negligible weights. In system 2, the electron-donor OCH3 on the diene and the electron-acceptor CN on the dienophile make more important the contributions of ionic Lewis structures that stabilize the transition state and determine the decrease of the reaction barrier with respect to system 1.

9.
Org Biomol Chem ; 18(5): 865-877, 2020 02 07.
Artigo em Inglês | MEDLINE | ID: mdl-31845697

RESUMO

A series of oligomers containing alternate l-Ala and pGlu (pyroglutamic acid) both in the L and D form have been prepared and conformationally investigated by X-ray, NMR, UV/ECD, IR/VCD and molecular modelling. X-ray diffraction analysis was possible for the shortest oligomers LL-1 and LD-1. Molecular dynamics simulations of the oligomers demonstrated that the energy landscapes of the LL-series are broad. In contrast, the energy landscapes of the LD-series are characterized by well-defined minima corresponding to specific conformational structures. A single well-defined minimum exists in the energy landscape of the largest oligomer LD-8, corresponding to a precise conformation, characterized by i + 5 →i N-HO[double bond, length as m-dash]C hydrogen bonds, typical of a π-helix. ECD and VCD spectra were measured to identify the chiroptical profiles of the oligomers. The most striking element in the ECD spectra of the LD-series is their exceptionally strong intensity, which confirms that these polypeptides attain a high degree of helical order. VCD spectra for the LD-series are well reproduced by frequency calculations when π-helix folds are employed as input structures, suggesting that a symmetrical VCD couplet around 1720 cm-1 can be taken as the VCD signature of π-helices.


Assuntos
Peptídeos/química , Dicroísmo Circular , Simulação de Dinâmica Molecular , Peptídeos/síntese química , Estrutura Secundária de Proteína , Espectroscopia de Infravermelho com Transformada de Fourier , Termodinâmica , Vibração
10.
Molecules ; 24(23)2019 Nov 28.
Artigo em Inglês | MEDLINE | ID: mdl-31795090

RESUMO

Supramolecular hydrogels, obtained from small organic molecules, may be advantageous over polymeric ones for several applications, because these materials have some peculiar properties that differentiate them from the traditional polymeric hydrogels, such as elasticity, thixotropy, self-healing propensity, and biocompatibility. We report here the preparation of strong supramolecular pseudopeptide-based hydrogels that owe their strength to the introduction of graphene in the gelling mixture. These materials proved to be strong, stable, thermoreversible and elastic. The concentration of the gelator, the degree of graphene doping, and the nature of the trigger are crucial to get hydrogels with the desired properties, where a high storage modulus coexists with a good thixotropic behavior. Finally, NIH-3T3 cells were used to evaluate the cell response to the presence of the most promising hydrogels. The hydrogels biocompatibility remains good, if a small degree of graphene doping is introduced.


Assuntos
Grafite/química , Hidrogéis/química , Fenômenos Mecânicos , Peptídeos/química , Fosfatidiletanolaminas/química , Animais , Materiais Biocompatíveis/química , Fenômenos Químicos , Concentração de Íons de Hidrogênio , Camundongos , Estrutura Molecular , Células NIH 3T3 , Reologia , Espectroscopia de Infravermelho com Transformada de Fourier
11.
Nanoscale ; 11(41): 19301-19314, 2019 Nov 07.
Artigo em Inglês | MEDLINE | ID: mdl-31626253

RESUMO

We investigate the photocatalytic performance of composites prepared in a one-step process by liquid-phase exfoliation of graphite in the presence of TiO2 nanoparticles (NPs) at atmospheric pressure and in water, without heating or adding any surfactant, and starting from low-cost commercial reagents. These show enhanced photocatalytic activity, degrading up to 40% more pollutants with respect to the starting TiO2-NPs, in the case of a model dye target, and up to 70% more pollutants in the case of nitrogen oxides. In order to understand the photo-physical mechanisms underlying this enhancement, we investigate the photo-generation of reactive species (trapped holes and electrons) by ultrafast transient absorption spectroscopy. We observe an electron transfer process from TiO2 to the graphite flakes within the first picoseconds of the relaxation dynamics, which causes the decrease of the charge recombination rate, and increases the efficiency of the reactive species photo-production.

12.
J Mater Chem B ; 7(38): 5808-5813, 2019 10 14.
Artigo em Inglês | MEDLINE | ID: mdl-31486471

RESUMO

The controlled release of cell differentiating agents is crucial in many aspects of regenerative medicine. Here we propose the use of hybrid calcite single crystals as micro-carriers for the controlled and localized release of retinoic acid, which is entrapped within the crystalline lattice. The release of retinoic acid occurs only in the proximity of stem cells, upon dissolution of the calcite hybrid crystals that are dispersed in the fibrin scaffold. These hybrid crystals provide a sustained dosage of the entrapped agent. The environment provided by this composite scaffold enables differentiation towards neuronal cells that form a three-dimensional neuronal network.


Assuntos
Carbonato de Cálcio/química , Diferenciação Celular , Fibrina/química , Tretinoína/química , Técnicas de Cultura de Células/métodos , Diferenciação Celular/efeitos dos fármacos , Linhagem Celular , Humanos , Concentração de Íons de Hidrogênio , Microscopia Eletrônica de Varredura , Neurônios/citologia , Células-Tronco/citologia , Células-Tronco/metabolismo , Tretinoína/metabolismo , Tretinoína/farmacologia
13.
Front Chem ; 7: 218, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31024902

RESUMO

Lanthanide-doped upconversion nanoparticles can convert long wavelength excitation radiation to short wavelength emission. They have great potential in biomedical applications, such as bioimaging, biodetection, drug delivery, and theranostics. However, there is little information available on their bioavailability and biological effects after oral administration. In this study, we systematically investigated the bioavailability, biodistribution, and toxicity of silica-coated upconversion nanoparticles administrated by gavage. Our results demonstrate that these nanoparticles can permeate intestinal barrier and enter blood circulation by microstructure observation of Peyer's patch in the intestine. Comparing the bioavailability and the biodistribution of silica-coated upconversion nanoparticles with oral and intravenous administration routes, we found that the bioavailability and biodistribution are particularly dependent on the administration routes. After consecutive gavage for 14 days, the body weight, pathology, Zn and Cu level, serum biochemical analysis, oxidative stress, and inflammatory cytokines were studied to further evaluate the potential toxicity of the silica-coated upconversion nanoparticles. The results suggest that these nanoparticles do not show overt toxicity in mice even at a high dose of 100 mg/kg body weight.

14.
J Chem Inf Model ; 59(4): 1547-1553, 2019 04 22.
Artigo em Inglês | MEDLINE | ID: mdl-30702292

RESUMO

The 9DB1 DNAzyme follows an addition-elimination (AN+DN) two-step mechanism, involving a phosphorane intermediate, where the 3'-hydroxyl group (nucleophile) of one RNA fragment attacks the 5'-triphosphate of another RNA fragment. This mechanism does not involve a divalent metal cation in agreement with the experimental evidence. The process is assisted by two proton transfers that activate the nucleophile (first step) and the leaving group (second step). The dA13 nucleotide is not directly involved in the reaction. However, it plays an important role in determining the regioselectivity of the process: since the dA13 phosphate forms a strong hydrogen bond with the 2'-hydroxyl, only the 3'-hydroxyl can behave as a nucleophile and form the new 3'-5' bond. In silico mutagenesis, where the dA13 phosphate oxygen involved in the hydrogen contact was replaced by a sulfur atom, causes a significant rearrangement of the A50 ribose position with an increase in the activation barrier and a consequent lower enzymatic activity in agreement with the experimental evidence. A similar effect is determined by the replacement of the 2'-hydroxyl with different groups such as F, H, and OMe.


Assuntos
DNA Catalítico/química , DNA Catalítico/metabolismo , Teoria da Densidade Funcional , Modelos Moleculares , Biocatálise , DNA , Ligação de Hidrogênio
15.
Proc Natl Acad Sci U S A ; 116(7): 2452-2457, 2019 02 12.
Artigo em Inglês | MEDLINE | ID: mdl-30683725

RESUMO

Three 819 knots in closed-loop strands of different lengths (∼20, 23, and 26 nm) were used to experimentally assess the consequences of knot tightness at the molecular level. Through the use of 1H NMR, diffusion-ordered spectroscopy (DOSY), circular dichroism (CD), collision-induced dissociation mass spectrometry (CID-MS) and molecular dynamics (MD) simulations on the different-sized knots, we find that the structure, dynamics, and reactivity of the molecular chains are dramatically affected by the tightness of the knotting. The tautness of entanglement causes differences in conformation, enhances the expression of topological chirality, weakens covalent bonds, inhibits decomplexation events, and changes absorption properties. Understanding the effects of tightening nanoscale knots may usefully inform the design of knotted and entangled molecular materials.

16.
Bioconjug Chem ; 30(3): 808-814, 2019 03 20.
Artigo em Inglês | MEDLINE | ID: mdl-30616344

RESUMO

The lack of solubility in water and the formation of aggregates hamper many opportunities for technological exploitation of C60. Here, different peptides were designed and synthesized with the aim of monomolecular dispersion of C60 in water. Phenylalanines were used as recognizing moieties, able to interact with C60 through π-π stacking, while a varying number of glycines were used as spacers, to connect the two terminal phenylalanines. The best performance in the dispersion of C60 was obtained with the FGGGF peptidic nanotweezer at a pH of 12. A full characterization of this adduct was carried out. The peptides disperse C60 in water with high efficiency, and the solutions are stable for months both in pure water and in physiological environments. NMR measurements demonstrated the ability of the peptides to interact with C60. AFM measurements showed that C60 is monodispersed. Electrospray ionization mass spectrometry determined a stoichiometry of C60@(FGGGF)4. Molecular dynamics simulations showed that the peptides assemble around the C60 cage, like a candy in its paper wrapper, creating a supramolecular host able to accept C60 in the cavity. The peptide-wrapped C60 is fully biocompatible and the C60 "dark toxicity" is eliminated. C60@(FGGGF)4 shows visible light-induced reactive oxygen species (ROS) generation at physiological saline concentrations and reduction of the HeLa cell viability in response to visible light irradiation.


Assuntos
Materiais Biocompatíveis/química , Fulerenos/química , Peptídeos/química , Células HeLa , Humanos , Concentração de Íons de Hidrogênio , Simulação de Dinâmica Molecular , Ressonância Magnética Nuclear Biomolecular , Espécies Reativas de Oxigênio/metabolismo , Água
17.
Org Lett ; 20(12): 3705-3709, 2018 06 15.
Artigo em Inglês | MEDLINE | ID: mdl-29863889

RESUMO

The graphene oxide (GO) assisted allylic alkylation of thiophenes with alcohols is presented. Mild reaction conditions and a low GO loading enabled the isolation of a range of densely functionalized thienyl and bithienyl compounds in moderate to high yields (up to 90%). The cooperative action of the Brønsted acidity, epoxide moieties, and π-surface of the 2D-promoter is highlighted as crucial in the reaction course of the present Friedel-Crafts-type protocol.

18.
Nanoscale ; 10(21): 9908-9916, 2018 May 31.
Artigo em Inglês | MEDLINE | ID: mdl-29790558

RESUMO

Hybrid systems have great potential for a wide range of applications in chemistry, physics and materials science. Conjugation of a biosystem to a molecular material can tune the properties of the components or give rise to new properties. As a workhorse, here we take a C60@lysozyme hybrid. We show that lysozyme recognizes and disperses fullerene in water. AFM, cryo-TEM and high resolution X-ray powder diffraction show that the C60 dispersion is monomolecular. The adduct is biocompatible, stable in physiological and technologically-relevant environments, and easy to store. Hybridization with lysozyme preserves the electrochemical properties of C60. EPR spin-trapping experiments show that the C60@lysozyme hybrid produces ROS following both type I and type II mechanisms. Due to the shielding effect of proteins, the adduct generates significant amounts of 1O2 also in aqueous solution. In the case of type I mechanism, the protein residues provide electrons and the hybrid does not require addition of external electron donors. The preparation process and the properties of C60@lysozyme are general and can be expected to be similar to other C60@protein systems. It is envisaged that the properties of the C60@protein hybrids will pave the way for a host of applications in nanomedicine, nanotechnology, and photocatalysis.


Assuntos
Fulerenos/química , Muramidase/química , Água/química , Detecção de Spin
19.
Materials (Basel) ; 11(5)2018 Apr 27.
Artigo em Inglês | MEDLINE | ID: mdl-29702620

RESUMO

The 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 C60 in 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.

20.
Chemphyschem ; 19(12): 1514-1521, 2018 06 19.
Artigo em Inglês | MEDLINE | ID: mdl-29665221

RESUMO

We investigated the catalytic mechanism of α-1,4-glucan lyases using a full QM DFT approach based on the M06-2X functional. The reaction profile of the whole catalytic process can be divided into three phases: glycosylation, deglycosylation-elimination and tautomerization. Glycosylation is a highly asynchronous SN 1-like process with an energy barrier of 10.2 kcal mol-1 . A proton moves from the Asp665 residue to the glycosidic oxygen. Asp553 acts as a nucleophile and attacks the anomeric carbon causing the cleavage of the glycosidic bond. Deglycosilation-elimination is the rate-determining step of the entire process with an overall barrier of 18.3 kcal mol-1 . The final step (restoring the catalyst and tautomerization) occurs rather easily, since the Asp553 carboxylate group "assists" the proton transfer in the tautomerization process. Our computations clearly indicate that tautomerization must occur inside the enzyme before leaving the active site rather than in the aqueous solution. Outside of the protein environment the enol-AF→keto-AF process "assisted" by a water molecule has a barrier of 35.8 kcal mol-1 .


Assuntos
Modelos Moleculares , Polissacarídeo-Liase/metabolismo , Teoria Quântica , Biocatálise , Glicosilação , Alga Marinha/enzimologia , Solventes/química , Termodinâmica
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