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Dynamic self-assembly is an emerging area of research where properly designed self-assembly elements can be used reversibly to trigger and control some tasks at the molecular level. The interactions between decorated nanoparticles, NPs, are experimentally modifiable by a variety of stimuli that can also vary in time periodically or randomly. In coarse-grained simulations, we activate a switch, either periodically or randomly, which assembles-disassembles clusters of NPs. We then introduce a single catalytic NP(C) covered with catalytic moieties, C, and leave all remaining NP(R)s decorated with reactive moieties, R. The catalytic reaction that converts R into products P depends on the encounter of C and R. Particle-based simulations are here used to study the catalytic activity and reaction yields of decorated nanoparticles that aggregate/disaggregate with the application of time-varying perturbations. Static aggregation is not catalytically efficient because it traps the catalyst. The application of random perturbations that vary in time in the form of colored noises improves the reaction yields and can provide opportunities for more efficient catalytic activity. The work can also allow us to understand how in Nature many biological processes are affected or driven by random/noisy fluctuations of the environment.

The lack of solubility in water and the formation of aggregates hamper many opportunities for technological exploitation of C 60 . Here, different peptides were designed and synthesized with the aim of monomolecular dispersion of C 60 in water. Phenylalanines were used as recognizing moieties, able to interact with C 60 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 C 60 was obtained with the FGGGF peptidic nanotweezer at a pH of 12. A full characterization of this adduct was carried out. The peptides disperse C 60 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 C 60 . AFM measurements showed that C 60 is monodispersed. Electrospray ionization mass spectrometry determined a stoichiometry of C 60 @(FGGGF) 4 . Molecular dynamics simulations showed that the peptides assemble around the C 60 cage, like a candy in its paper wrapper, creating a supramolecular host able to accept C 60 in the cavity. The peptide-wrapped C 60 is fully biocompatible and the C 60 "dark toxicity" is eliminated. C 60 @(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.

A bis-tryptophan tweezer was installed on a polyoxometalate (POM) surface via a bis-amide covalent bond, yielding the enantiopure hybrid POM with C2 symmetry, as a result of the regioselective functionalization of decatungosilicate [γ-SiW10O36]8– at the lacunary site. The combined polyanionic and receptor properties are instrumental for a POM-driven solubilization and enrichment of single walled carbon nanotubes (SWCNTs) with diameter

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.

We carried out a computational investigation at the density functional theory (M06-2X) level on the effects of oriented external electric fields (OEEF) on activation barriers and stereochemical output of the thermal ring opening of 3-substituted cyclobutenes (C4H5X) to butadienes. It is well known that with π-electron-donor substituents (X = CH3, NH2), the conrotatory outward rotation is preferred, while with π-electron-acceptor substituents (X = CHO, NO, BH2), the conrotatory inward process becomes favored. In the presence of the OEEF applied along the three axes x, y, and z in either positive or negative direction, for both π-donor and π-acceptor substituents, we observed either catalysis or inhibition. Both effects were consistent with the change of the induced dipole along the direction of the applied field. An interesting effect was observed for X = CHO and NO. The simultaneous catalysis and inhibition of the outward and inward transformation leads to a reversed ratio between outward and inward transformation, with the former being favored (stereochemical inversion). Such effect was not observed for X = BH2 (the strongest π-acceptor examined here). In this case, in the absence of the applied field, the difference between the inward and outward barriers is too large and the simultaneous catalysis and inhibition of the outward and inward transformation is not capable of determining the stereochemical inversion.

Item does not contain fulltext 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.

Fullerenes are candidates for theranostic applications because of their high photodynamic activity and intrinsic multimodal imaging contrast. However, fullerenes suffer from low solubility in aqueous media, poor biocompatibility, cell toxicity, and a tendency to aggregate. C70@lysozyme is introduced herein as a novel bioconjugate that is harmless to a cellular environment, yet is also photoactive and has excellent optical and optoacoustic contrast for tracking cellular uptake and intracellular localization. The formation, water-solubility, photoactivity, and unperturbed structure of C70@lysozyme are confirmed using UV-visible and 2D 1H, 15N NMR spectroscopy. The excellent imaging contrast of C70@lysozyme in optoacoustic and third harmonic generation microscopy is exploited to monitor its uptake in HeLa cells and lysosomal trafficking. Last, the photoactivity of C70@lysozyme and its ability to initiate cell death by means of singlet oxygen (1O2) production upon exposure to low levels of white light irradiation is demonstrated. This study introduces C70@lysozyme and other fullerene-protein conjugates as potential candidates for theranostic applications.

Mechanobiology is an important epigenetic factor. It influences cell functioning and bears on gene induction, protein synthesis, cell growth, and differentiation. In the presence of patterned chemical cues, living cells can take shapes that are far from that of a drop of fluid. These shapes are characterized by inward curvatures that are pinned at the points of location of the cues. The mechanochemical interactions that orchestrate cell behavior is simulated and controlled by modeling the cells as made by parcels of fluid. Cells become drops that are then endowed with the presence of additional forces, generated on the fly, that effectively make them active. With the proper choice of the forces, the phenomena that emerge from the dynamics match quantitatively the experiments. A combination of hydrophilic and lipophilic forces acting between the beads of fluid allows the active drop to respond to patterned cues and form squares, pentagons, hexagons, and flowers, just as living cells do.

Submarine volcanoes, such as Kolumbo (Santorini, Greece) are natural laboratories for fostering multidisciplinary studies. Their investigation requires the most innovative marine technology together with advanced data analysis. Conductivity and temperature of seawater were recorded directly above Kolumbo’s hydrothermal vent system. The respective time series have been analyzed in terms of non–equilibrium techniques. The energy dissipation of the volcanic activity is monitored by the temperature variations of seawater. The venting dynamics of chemical products is monitored by water conductivity. The analysis of the time series in terms of stochastic processes delivers scaling exponents with turning points between consecutive regimes for both conductivity and temperature. Changes of conductivity are shown to behave as a universal multifractal and their variance is subdiffusive as the scaling exponents indicate. Temperature is constant over volcanic rest periods and a universal multifractal behavior describes its changes in line with a subdiffusive character otherwise. The universal multifractal description illustrates the presence of non–conservative conductivity and temperature fields showing that the system never retains a real equilibrium state. The existence of a repeated pattern of the combined effect of both seawater and volcanic activity is predicted. The findings can shed light on the dynamics of chemical products emitted from the vents and point to the presence of underlying mechanisms that govern potentially hazardous, underwater volcanic environments.

none 3 no Electric field; Density functional theory; organic field effect transistors; dimerization process Density functional theory (DFT) calculations were used to assess the effect of electric fields of varying magnitudes and directions on the molecular structure of pentacene and other acenes. The aim is to understand the response of acenes in organic field effect transistors, specifically the structure of the first monolayer(s) deposited on the gate dielectric, where the transversal electric field and the charge carrier density are largest and charge transport occurs. Pentacene cycloaddition can be enhanced by the application of electric fields oriented along the direction of the forming bonds. Dimerization is likely to occur in low-density, disordered domains, such as grain boundaries or terrace edges. Together with other factors, dimerization could affect device performance leading to an irreversible decrease of mobility due to the creation of new trap states. Matta, Micaela; Biscarini, Fabio; Zerbetto, Francesco Matta, Micaela; Biscarini, Fabio; Zerbetto, Francesco

Photoelectron spectroscopy is usually described by a simple equation that relates the binding energy of the photoemitted electron, E-binding, its kinetic energy, E-kinetic, the energy of the ionizing photon, E-photon, and the work function of the spectrometer, phi, E-binding = E-photon - E-kinetic - phi. Behind this equation there is an extremely rich physics, which we describe here using as an example a relatively simple conjugated molecule, namely coronene. The theoretical analysis of valence band and C1s core level photoemission spectra showed that multiple excitations play an important role in determining the intensities of the final spectrum. An explicit, time-evolving model is applied, which is able to count all possible photo-excitations occurring during the photoemission process, showing that they evolve on a short time-scale, of about 10 fs. The method reveals itself to be a valid approach to reproduce photoemission spectra of polycyclic aromatic hydrocarbons (PAHs).

Enzymatic reactions in complex environments often take place with concentrations of enzyme comparable to that of substrate molecules. Two such cases occur when an enzyme is used to detect low concentrations of substrate/analyte or inside a living cell. Such concentrations do not agree with standard in vitro conditions, aimed at satisfying one of the founding hypotheses of the Michaelis-Menten reaction scheme, MM. It would be desirable to generalize the classical approach and show its applicability to complex systems. A permeable micrometrically structured hydrogel matrix was fabricated by protein cross-linking. Glucose oxidase enzyme (GOx) was embedded in the matrix and used as a prototypical system. The concentration of H2O2 was monitored in time and fitted by an accurate solution of the enzymatic kinetic scheme, which is expressed in terms of simple functions. The approach can also find applications in digital microfluidics and in systems biology where the kinetics response in the linear regimes often employed must be replaced.

Drops and biological cells share some morphological features and visco-elastic properties. The modelling of drops by mesoscopic non-atomistic models has been carried out to a high degree of success in recent years. We extend such treatment and discuss a simple, drop-like model to describe the interactions of the outer layer of cells with the surfaces of materials. Cells are treated as active mechanical objects that are able to generate adhesion forces. They appear with their true size and are made of "parcels of fluids" or beads. The beads are described by (very) few quantities/parameters related to fundamental chemical forces such as hydrophilicity and lipophilicity that represent an average of the properties of a patch of material or an area of the cell(s) surface. The investigation of adhesion dynamics, motion of individual cells, and the collective behavior of clusters of cells on materials is possible. In the simulations, the drops become active soft matter objects and different from regular droplets they do not fuse when in contact, their trajectories are not Brownian, and they can be forced "to secrete" molecules, to name some of the properties targeted by the modeling. The behavior that emerges from the simulations allows ascribing some cell properties to their mechanics, which are related to their biological features.

Tuning the intermolecular interactions among suitably designed molecules forming highly ordered self-assembled monolayers is a viable approach to control their organization at the supramolecular level. Such a tuning is particularly important when applied to sophisticated molecules combining functional units which possess specific electronic properties, such as electron/energy transfer, in order to develop multifunctional systems. Here we have synthesized two tetraferrocene-porphyrin derivatives that by design can selectively self-assemble at the graphite/liquid interface into either face-on or edge-on monolayer-thick architectures. The former supramolecular arrangement consists of two-dimensional planar networks based on hydrogen bonding among adjacent molecules whereas the latter relies on columnar assembly generated through intermolecular van der Waals interactions. Scanning Tunneling Microscopy (STM) at the solid-liquid interface has been corroborated by cyclic voltammetry measurements and assessed by theoretical calculations to gain multiscale insight into the arrangement of the molecule with respect to the basal plane of the surface. The STM analysis allowed the visualization of these assemblies with a sub-nanometer resolution, and cyclic voltammetry measurements provided direct evidence of the interactions of porphyrin and ferrocene with the graphite surface and offered also insight into the dynamics within the face-on and edge-on assemblies. The experimental findings were supported by theoretical calculations to shed light on the electronic and other physical properties of both assemblies. The capability to engineer the functional nanopatterns through self-assembly of porphyrins containing ferrocene units is a key step toward the bottom-up construction of multifunctional molecular nanostructures and nanodevices.

The analysis of the interaction between C60 and lysozyme provides general rules to identify the forces that govern the thermodynamics of binding between proteins and carbon nanoparticles. The main driving force of the binding are van der Waals interactions. Polar solvation and entropy, contributions that are often neglected, are strongly detrimental to the binding. These energetically relevant terms must be taken into account when protein/CNP hybrids are designed.

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.

The morphology and the activity of a submarine caldera, Avyssos, at the northern part of Nisyros volcano in the South Aegean Sea (Greece), has been studied by means of remotely operated underwater vehicle dives. The recorded time series of temperature and conductivity over the submarine volcano have been analyzed in terms of the Generalized Moments Method. The findings of the mathematical analysis shed light on the volcanic activity, but also on the morphology (shape) of the submarine volcano. The conductivity time series indicates the volcano is at rest in agreement with other types of observations. On the other hand, temperature fluctuations, which in general describe a multifractal process, show that the submarine caldera operates as an open system that interacts with its surroundings. This type of analysis can be used as an indicator for the state of activity and the morphological structure (closed or open system) of a submarine volcano.

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.

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.

Photovoltaics is one of the key areas in renewable energy research with remarkable progress made every year. Here we consider the case of a photoactive material and study its structural composition and the resulting consequences for the fundamental processes driving solar energy conversion. A multiscale approach is used to characterize essential molecular properties of the light-absorbing layer. A selection of bulk-representative pairs of donor/acceptor molecules is extracted from the molecular dynamics simulation of the bulk heterojunction and analyzed at increasing levels of detail. Significantly increased ground state energies together with an array of additional structural characteristics are identified that all point towards an auxiliary role of the material's structural organization in mediating charge-transfer and -separation. Mechanistic studies of the type presented here can provide important insights into fundamental principles governing solar energy conversion in next-generation photovoltaic devices.

Fe-EDDHSA/CaCO

The widespread occurrence of Indian yellow on an early 17th-century wall painting in Rajasthan (India) was initially indicated by photo-induced luminescence imaging of the painted scheme in the Badal Mahal within the Garh Palace (Bundi). The presence of the organic pigment was subsequently confirmed by HPLC-ESI-Q-ToF. The results of a multi-analytical study focusing on two samples from the wall painting and two reference pigments from the British Museum and National Gallery (London, UK) are presented here. The research focused on the possible causes for the different yellow/orange hues observed in the painting samples. Analysis of cross-sections with SEM-EDS revealed similar elemental composition for the Indian yellow paint layers, but different underlying layers, indicating a variation in painting technique. The composition of the Indian yellow samples was investigated by HPLC-ESI-Q-ToF with both positive and negative ionisation. In addition to euxanthic acid and euxanthone, a sulphonate derivative of euxanthone was found to be present in all samples, while relative amounts of the three components varied. Flavonoid molecules—morin, kaempferol, quercetin and luteolin—were also detected in one wall painting sample (characterised by a brighter yellow colour) and not in the sample that was more orange. The optical properties of the samples were characterised by photoluminescence spectroscopy in both solid state and aqueous solution. The contribution of each organic compound to the emission spectrum of Indian yellow in solution was also investigated by time-dependent density functional theory (TDDFT) calculations. Small differences in terms of spectral shift were observed in solid state experiments, but not in solution, suggesting that the spectral differences in the emission spectrum were mostly due to different contributions of solid-state arrangements, most likely driven by π-π stacking and/or hydrogen bonds. However, a slight difference at high energies was observed in the spectra acquired in solution and TDDFT calculations permitted this to be ascribed to the different chemical composition of the samples. Time-resolved measurements highlighted di-exponential lifetime decays, confirming the presence of at least two molecular arrangements. Py(HMDS)-GC–MS was also used for the first time to characterise Indian yellow and the trimethylsilyl derivative of euxanthone was identified in the pyrograms, demonstrating it to be a suitable marker for the identification of the pigment in complex historic samples.

reserved 10 no G. F. and M. C. thank Consorzio Interuniversitario di Ricerca sulla Chimica dei Metalli nei Sistemi Biologici for the support. Fe-EDDHSA/CaCO3 hybrid crystals are synthesized and tested in vitro to determine their effect in treating iron chlorosis in kiwifruit plants, used as a proof of concept. Under the alkaline conditions provided by the calcareous substrate, plants release protons that dissolve the hybrids and trigger Fe uptake. These CaCO3 hybrids represent a new system for active molecule delivery in agriculture. mixed Baldi, Elena; Marino, Grazia; Toselli, Moreno; Marzadori, Claudio; Ciavatta, Claudio; Tavoni, Marta; Di Giosia Matteo, ; Calvaresi, Matteo; Falini, Giuseppe; Zerbetto, Francesco Baldi, Elena; Marino, Grazia; Toselli, Moreno; Marzadori, Claudio; Ciavatta, Claudio; Tavoni, Marta; Di Giosia Matteo, ; Calvaresi, Matteo; Falini, Giuseppe; Zerbetto, Francesco

Cell shape is a valuable indicator of cell health status and interactions with the extracellular materials. With the aim to investigate how individual cells respond to chemical microenvironments, we employed 2D monomolecular layers of small organic molecules, characterized by very low roughness. MCF10A cells were grown on these surfaces and characterized by using scanning electrochemical microscopy. The single cell morphologies were analyzed to define a "figure of merit" for the different cell-surface interactions. Such "figure of merit" quantifies the interaction with the microenvironment. This method is applicable to any cell state (metastatic, physiological or pathological) and any surface.

Background High levels of blood cholesterol are conventionally linked to an increased risk of developing cardiovascular disease (Grundy, 1986). Here we examine the molecular mode of action of natural products with known cholesterol-lowering activity, such as for example the green tea ingredient epigallocatechin gallate and a short pentapeptide, Ile-Ile-Ala-Glu-Lys. Methods Molecular Dynamics simulations are used to gain insight into the formation process of mixed micelles and, correspondingly, how active agents epigallocatechin gallate and Ile-Ile-Ala-Glu-Lys could possibly interfere with it. Results Self-assembly of physiological micelles occurs on the order of 35–50 ns; most of the structural properties of mixed micelles are unaffected by epigallocatechin gallate or Ile-Ile-Ala-Glu-Lys which integrate into the micellar surface; the diffusive motion of constituting lipids palmitoyl-oleoyl-phosphatidylcholine and cholesterol is significantly down-regulated by both epigallocatechin gallate and Ile-Ile-Ala-Glu-Lys; Conclusions The molecular mode of action of natural compounds epigallocatechin gallate and Ile-Ile-Ala-Glu-Lys is a significant down-regulation of the diffusive motion of micellar lipids. General significance Natural compounds like the green tea ingredient epigallocatechin gallate and a short pentapeptide, Ile-Ile-Ala-Glu-Lys, lead to a significant down-regulation of the diffusive motion of micellar lipids thereby modulating cholesterol absorption into physiological micelles.

Carbon Nanotubes, CNTs, have been described as rolled-up graphene layers. Matching this concept to experiments has been a great experimental challenge for it requires a method to exfoliate graphite, generate ordered and stable dangling carbon bonds, and roll up the layer without affecting the un-paired electrons of the dangling bonds that finally have to zip up in an orderly fashion: A tall order for any synthetic strategy. The combined use of ultrasonication of graphite in dimethylformamide and addition of ferrocene aldehyde just does it!

Molecular dynamics simulations of C60on Au(1 1 1) reveal that the molecular diffusion consists of randomsequences of stick, slide, and stick and slip periods. Stochastic analysis of forty trajectories shows thatinitially C60 follows a super-diffusive-sub-ballistic-like motion, which then turns into super-diffusive.Individual trajectories present a variety of diffusive motions that even include subdiffusion. The analysisof the displacement moments indicates Fractional Brownian motion (FBM), as underlying stochastic-mechanism, a finding further supported by the analysis of the velocity correlation function.

Molecular dynamics--coarse grained to the level of hydrophobic and hydrophilic interactions--shows that small hydrophobic graphene sheets pierce through the phospholipid membrane and navigate the double layer, intermediate size sheets pierce the membrane only if a suitable geometric orientation is met, and larger sheets lie mainly flat on the top of the bilayer where they wreak havoc with the membrane and create a patch of upturned phospholipids. The effect arises in order to maximize the interaction between hydrophobic moieties and is quantitatively explained in terms of flip-flops by the analysis of the simulations. Possible severe biological consequences are discussed.

In systems having an anisotropic electronic structure, such as the layered materials graphite, graphene, and cuprates, impulsive light excitation can coherently stimulate specific bosonic modes, with exotic consequences for the emergent electronic properties. Here we show that the population of E_{2g} phonons in the multiband superconductor MgB_{2} can be selectively enhanced by femtosecond laser pulses, leading to a transient control of the number of carriers in the σ-electronic subsystem. The nonequilibrium evolution of the material optical constants is followed in the spectral region sensitive to both the a- and c-axis plasma frequencies and modeled theoretically, revealing the details of the σ-π interband scattering mechanism in MgB_{2}.

Amphiphilic small molecules and polymers form commonplace nanoscale macromolecular compartments and bilayers, and as such are truly essential components in all cells and in many cellular processes. The nature of these architectures, including their formation, phase changes, and stimuli-response behaviors, is necessary for the most basic functions of life, and over the past half-century, these natural micellar structures have inspired a vast diversity of industrial products, from biomedicines to detergents, lubricants, and coatings. The importance of these materials and their ubiquity have made them the subject of intense investigation regarding their nanoscale dynamics with increasing interest in obtaining sufficient temporal and spatial resolution to directly observe nanoscale processes. However, the vast majority of experimental methods involve either bulk-averaging techniques including light, neutron, and X-ray scattering, or are static in nature including even the most advanced cryogenic transmission electron microscopy techniques. Here, we employ in situ liquid-cell transmission electron microscopy (LCTEM) to directly observe the evolution of individual amphiphilic block copolymer micellar nanoparticles in solution, in real time with nanometer spatial resolution. These observations, made on a proof-of-concept bioconjugate polymer amphiphile, revealed growth and evolution occurring by unimer addition processes and by particle-particle collision-and-fusion events. The experimental approach, combining direct LCTEM observation, quantitative analysis of LCTEM data, and correlated in silico simulations, provides a unique view of solvated soft matter nanoassemblies as they morph and evolve in time and space, enabling us to capture these phenomena in solution.

Of all the amino acids, the surface of π-electron conjugated carbon nanoparticles has the largest affinity for tryptophan, followed by tyrosine, phenylalanine, and histidine. In order to increase the binding of a protein to a fullerene, it should suffice to mutate a residue of the site that binds to the fullerene to tryptophan, Trp. Computational chemistry shows that this intuitive approach is fraught with danger. Mutation of a binding residue to Trp may even destabilize the binding because of the complicated balance between van der Waals, polar and non-polar solvation interactions.

none 9 si The optical properties (photophysics and imaging) of Indian yellow were investigated both in solid state and in aqueous solution and correlated with its chemical composition. The analyses were corroborated by a theoretical study carried out on the different xanthone derivatives that comprise the pigment under investigation, both as isolated molecules and in a polar (protic) solvent, to help the assignment of the excited states involved in the photo-induced process. Knowledge of its relatively high photoluminescence quantum yield (PLQY 0.6%), excitation and emission spectra and lifetime decays enhances the potential for reliable identification using non-invasive photo-induced luminescence imaging techniques. New insights into the chemical composition of the pigment, such as the identification of a sulphonate derivative of euxanthone, and its extensive occurrence on a 17th-century Indian wall painting are also reported for the first time in this study. Martin de Fonjaudran, Charlotte; Acocella, Angela; Accorsi, Gianluca; Tamburini, Diego; Verri, Giovanni; Rava, Amarilli; Whittaker, Samuel; Zerbetto, Francesco; Saunders, David Martin de Fonjaudran, Charlotte; Acocella, Angela; Accorsi, Gianluca; Tamburini, Diego; Verri, Giovanni; Rava, Amarilli; Whittaker, Samuel; Zerbetto, Francesco; Saunders, David

The studies on surface chemical gradients are constantly gaining interest both for fundamental studies and for technological implications in materials science, nanofluidics, dewetting, and biological systems. Here we report on a new approach that is very simple and very efficient, to fabricate surface chemical gradients of alkanethiols, which combines electrochemical desorption/partial readsorption, with the withdrawal of the surface from the solution. The gradient is then stabilized by adding a complementary thiol terminated with a hydroxyl group with a chain length comparable to desorbed thiols. This procedure allows us to fabricate a chemical gradient of the wetting properties and the substrate work-function along a few centimeters with a gradient slope higher than 5°/cm. Samples were characterized by cyclic voltammetry during desorption, static contact angle, XPS analysis, and Kelvin probe. Computer simulations based on the Dissipative Particle Dynamics methods were carried out considering a water droplet on a mixed SAM surface. The results help to rationalize the composition of the chemical gradient at different position on the Au surface.

The carbon nanotube (CNT)-confined chloride exchange SN2 reaction for methyl chloride has been examined using either a full quantum mechanical (QM) DFT approach based on the M06-2X functional or a hybrid approach where a (6,6) CNT is satisfactorily described by the molecular mechanics (MM) UFF force field and the substrate by the M06-2X functional (M06-2X/UFF approach). We found that inside the CNT the reaction is disfavored with respect to the gas phase, the intrinsic reaction barrier Ea (difference between the preliminary complex I and transition state TS) being 17.9 kcal mol–1 (13.2 kcal mol–1 in the gas phase). The augmented barrier, with respect to the gas phase, can be ascribed to a complex interplay between Cl···π and C–H···π interactions (i.e., interactions of the two Cl atoms and the C–H bonds of the substrate with the carbon electron cloud of the tube wall). While the Cl···π interactions behave like a molecular glue which sticks the two Cl atoms to the tube wall and remain approximately constant in I and TS, the importance of the stabilizing C–H···π interactions is significantly lower in TS with a consequent increase of the barrier. The barrier increases with the increase of the tube length to reach the asymptotic value of 19.9 kcal mol–1 for tube length larger than 24.4 Å. This value is the minimum length of a (6,6) CNT model system that can emulate the CNT-confined SN2 reaction and provides useful suggestions to build reliable model systems for other SN2 reactions and, in general, different chemical processes. Furthermore, the activation barrier Ea is strongly affected by the tube radius. Because of the reduced volume inside the tube causing a strong structural distortion in TS, Ea is very large for small tube radii (34.4 kcal mol–1 in the (4,4) case). When the volume increases enough (tube (5,5)) to avoid the distortion, the barrier suddenly decreases and remains approximately constant (about 20 kcal mol–1) for tubes in the range (5,5) to (8,8). The activation barrier grows for a (9.9) tube, and the value again remains approximately constant (about 22 kcal mol–1) for larger tubes.

A simple, versatile, rapid, and inexpensive procedure based on the immersion method is developed to fabricate chemical gradients on chemically activated Si/SiO2 surfaces by a trichloro (1H,1H,2H,2H-perfluorooctyl) silane self-assembly monolayer (SAM). Contact angle measurements, atomic force microscopy, and X-ray photoelectron spectroscopy data based on the intensity of the signals of C1s and F1s, which progressively increase, indicate that the surface is characterized by the presence of increasing amounts of the SAM along the gradient direction. Experimental conditions are optimized by maximizing the variation of the contact angle of water drops at the starting and the ending points of the gradient. The application of the chemical gradient to droplet motion is demonstrated. The results are rationalized by dissipative particle dynamics simulations that well match the observed contact angles and the velocities of the drops. The simulations also show that the intrinsic nature of the gradient affects the velocity of the motion.

The short answer to the title question is no. Despite their tremendous complexity, many nanomachines are simply one-dimensional systems undergoing a biased, that is, unidirectional, walk on a two-minima potential energy curve. The initially prepared state, or station, is higher in energy than the final equilibrium state that is reached after overcoming an energy barrier. All chemical reactions comply with this scheme, which does not necessarily imply that a generic chemical reaction is a potential molecular motor. If the barrier is low, the system may walk back and the motion will have a large purely Brownian component. Alternatively, a large distance from the barrier of either of the two stations may introduce a Brownian component. Starting from a general inequality that leverages on the idea that the amount of heat dissipated along the potential energy curve is a good indication of the effectiveness of the biased walk, we provide guidelines for the selection of the features of artificial molecular motors.

LAC (hydroxylactone (1R,5S)-1-hydroxy-3,6-dioxabicyclo[3.2.1]octan-2-one) is one of the most interesting products of the pyrolysis of cellulose and represents a useful chiral building block in organic synthesis. A computational investigation at the DFT level on the mechanism of formation of LAC shows that this species can be obtained following two reaction paths, path A and path B, starting from a well-known pyrolysis product (ascopyrone P). A series of internal rearrangements involving in all cases a proton transfer leads directly to LAC (path B). An alternative path (path A) can be also followed. From this path, via a "gate" connecting the two reaction channels, it is possible to reach path B and form LAC. In both cases, the rate-determining step of the process is the initial keto-enol isomerization. We found that water, which is present in the reaction mixture, "catalyzes" the reaction by assisting the proton transfers present in all the steps of the process. In particular, water lowers the barrier of the rate-determining step that becomes 40.9 kcal mol-1 (79.4 kcal mol-1 in the absence of water). The corresponding computed rate constant is 4.3×10 s-1 at 500 °C, a value which is consistent with the presence of LAC in the absence of metal catalysts. The results of this study on the non-catalyzed process underpin the important role played by water in the formation of pyrolysis products of cellulose where proton transfer is a key mechanistic step.

Full geometry optimization has been performed within the semiempirical QCFF/PI model for the 1812 fullerene structural isomers of C{sub 60} formed by 12 pentagons and 20 hexagons. All are local minima on the potential energy hypersurface. Correlations of total energy with many structural motifs yield highly scattered diagrams, but some exhibit linear trends. Penalty and merit functions can be assigned to certain motifs: inclusion of a fused pentagon pair entails an average penalty of 111 kJ mol{sup -1}; a generic hexagon triple costs 23 kJ mol{sup -1}; a triple (open or fused) comprising a pentagon between two hexagonal neighbors gives a stabilization of 19 kJ mol{sup -1}. These results can be understood in terms of the curved nature of fullerene molecules: pentagons should be isolated to avoid sharp local curvature, hexagon triples are costly because they enforce local planarity and hence imply high curvature in another part of the fullerene surface, but hexagon-pentagon-hexagon triples allow the surface to distribute steric strain by warping. The best linear fit is found for H, the second moment of the hexagon-neighbor-index signature, which fits the total energies with a standard deviation of only 53 kJ mol{sup -1} and must be minimized for stability; thismore » index too can be interpreted in terms of curvature. 26 refs., 5 figs.« less

C 76 has 19151 possible fullerene structural isomers of which up to 55 are compatible with the experimental 19-line 13 C NMR spectrum, but only two have isolated pentagons. Calculations of the relative energies of all 55 candidates within the semi-empirical QCFF/PI model pick out the isolated-pentagon D 2 isomer as the structure of lowest energy for C 76 , confirming previous calculations and providing support for the isolated-pentagon rule. Energy differences between isomers of C 76 are interpreted in the model as torsional strains induced by pentagon adjacencies.

Scanning electrochemical microscopy (SECM) can image graphene oxide (GO) flakes on insulating and conducting substrates. The contrast between GO and the substrate is controlled by the electrostatic interactions that are established between the charges of the molecular redox mediator and the charges present in the sheet/substrate. SECM also allows quantitative measurement - at the nano/microscale - of the charge transfer kinetics between single monolayer sheets and agent molecules.

A 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.

International audience; In Double-Walled-Carbon-Nanotubes (DWCNTs) the outer shell screens the inner one fromthe external environment. As a consequence, the electronic properties of the smaller tubeare enhanced and DWCNTs have therefore been advocated for a number of uses. In theirraw form theymay contain small metallic clusters, left over from the catalytic process, thatcan give them a redox activity characterized by redox potentials in the range of onehundred millivolts and able to affect biological systems. Indeed, we find that redox activeraw-DWCNTs inhibit rat colorectal cancer cell proliferation by blocking cells in the G2phase through ROS generation by tumor cells. We show that raw-DWCNTs could alsomodulate autophagy in tumor cells through induction of intracellular acidification. Tothe best of our knowledge, this is the first time that DWCNTs have been found to inhibitproliferation and modulate autophagy in cancer cells. Our work further supports previousstudies that provided promising results on the possibility of future applications of CarbonNanotubes (CNTs) in nanomedicine.

Two epimeric series of foldamers characterized by the presence of a repeating alpha-epsilon-dipeptide unit have been prepared and characterized by 1H NMR and ECD spectroscopies together with X-ray diffraction. The first series contains L-Ala and D-4-carboxy-5-methyl-oxazolidin-2-one (D-Oxd). The other series contains L-Ala and L-Oxd. The L,D series of oligomers forms ordered beta-turn foldamers, characterized by a 311 pattern. The L,L series is not ordered. Simulations show that an ordered L,L trimer lies more than 2 kcal/mol higher than the more stable non folded extended conformations. Cu2+ forms complexes with both series, but is not able to order the L,L series. Analysis of the EPR spectra shows that the L,D foldamers bear two types of complexation sites that are assigned as a nitrogen donor of the triazole ring and a carboxylate ligand. The L-Ala-D-Oxd-Tri-CO motif may be introduced in any peptide sequence requiring the presence of a stable β-turn conformations, like in the study of protein-protein interactions.

none 14 si Biorecognition is a central event in biological processes in the living systems that is also widely exploited in technological and health applications. We demonstrate that the Electrolyte Gated Organic Field Effect Transistor (EGOFET) is an ultrasensitive and specific device that allows us to quantitatively assess the thermodynamics of biomolecular recognition between a human antibody and its antigen, namely, the inflammatory cytokine TNFα at the solid/liquid interface. The EGOFET biosensor exhibits a superexponential response at TNFα concentration below 1 nM with a minimum detection level of 100 pM. The sensitivity of the device depends on the analyte concentration, reaching a maximum in the range of clinically relevant TNFα concentrations when the EGOFET is operated in the subthreshold regime. At concentrations greater than 1 nM the response scales linearly with the concentration. The sensitivity and the dynamic range are both modulated by the gate voltage. These results are explained by establishing the correlation between the sensitivity and the density of states (DOS) of the organic semiconductor. Then, the superexponential response arises from the energy-dependence of the tail of the DOS of the HOMO level. From the gate voltage-dependent response, we extract the binding constant, as well as the changes of the surface charge and the effective capacitance accompanying biorecognition at the electrode surface. Finally, we demonstrate the detection of TNFα in human-plasma derived samples as an example for point-of-care application. Berto, Marcello; Casalini, Stefano; Di Lauro, Michele; Marasso, Simone L; Cocuzza, Matteo; Perrone, Denis; Pinti, Marcello; Cossarizza, Andrea; Pirri, Candido F; Simon, Daniel T; Berggren, Magnus; Zerbetto, Francesco; Bortolotti, Carlo A; Biscarini, Fabio Berto, Marcello; Casalini, Stefano; Di Lauro, Michele; Marasso, Simone L; Cocuzza, Matteo; Perrone, Denis; Pinti, Marcello; Cossarizza, Andrea; Pirri, Candido F; Simon, Daniel T; Berggren, Magnus; Zerbetto, Francesco; Bortolotti, Carlo A; Biscarini, Fabio

A limited class of aquaporins has been described to form regular arrays and junctions in membranes. The biological significance of these structures, however, remains uncertain. Here we analyze the underlying physical principles with the help of a computational procedure that takes into account protein–protein as well as protein–membrane interactions. Experimentally observed array/junction structures are systematically (dis)assembled and major driving forces identified. Aquaporin 4 was found to be markedly different from the non-junction forming aquaporin 1. The environmental stabilization resulting from embedding into the biomembrane was identified as the main driving force. This highlights the role of protein–membrane interactions in aquaporin 4. Analysis of the type presented here can help to decipher the biological role of membrane arrays and junctions formed by aquaporin.

We report the direct formation of multiwalled carbon nanotubes (MWNT) by ultrasonication of graphite in dimethylformamide (DMF) upon addition of ferrocene aldehyde (Fc-CHO). The tubular structures appear exclusively at the edges of graphene layers and contain Fe clusters. Pc in conjunction with benzyl aldehyde, or other Fc derivatives, does not induce formation of NT. Higher amounts of Fc-CHO added to the dispersion do not increase significantly MWNT formation. Increasing the temperature reduces the amount of formation of MWNTs and shows the key role of ultrasound-induced cavitation energy. It is concluded that Fc-CHO first reduces the concentration of radical reactive species that slice graphene into small moieties, localizes itself at the edges of graphene, templates the rolling up of a sheet to form a nanoscroll, where it remains trapped, and finally accepts and donates unpaired electron to the graphene edges and converts the less stable scroll into a MWNT. This new methodology matches the long held notion that CNTs are rolled up graphene layers. The proposed mechanism is general and will lead to control the production of carbon nanostructures by simple ultrasonication treatments.