Search

By incorporating 1-(2-aminoethyl)piperazine (AEPIP) into a commercial epoxy blend, a bi-continuous microstructure is produced with selective localization of amine-functionalized graphene nanoplatelets (A-GNPs). This cured blend underwent self-assembly, and the morphology and topology were observed via spectral imaging techniques. As the selective localization of nanofillers in thermoset blends is rarely achieved, and the mechanism remains largely unknown, the optical photothermal infrared (O-PTIR) spectroscopy technique was employed to identify the compositions of microdomains. The A-GNP tends to be located in the region containing higher concentrations of both secondary amine and secondary alcohol; additionally, the phase morphology was found to be influenced by the amine concentration. With the addition of AEPIP, the size of the graphene domains becomes smaller and secondary phase separation is detected within the graphene domain evidenced by the chemical contrast shown in the high-resolution chemical map. The corresponding chemical mapping clearly shows that this phenomenon was mainly induced by the chemical contrast in related regions. The findings reported here provide new insight into a complicated, self-assembled nanofiller domain formed in a multi-component epoxy blend, demonstrating the potential of O-PTIR as a powerful and useful approach for assessing the mechanism of selectively locating nanofillers in the phase structure of complex thermoset systems.

Assembly of nanoscale objects into linear architectures resembling molecular polymers is a basic organization resulting from divalent interactions. Such linear architectures occur for particles with two binding patches on opposite sides, known as Janus particles. However, unlike molecular systems where valence bonds can be envisioned as pointlike interactions nanoscale patches are often realized through multiple molecular linkages. The relationship between the characteristics of these linkages, the resulting interpatch connectivity, and assembly morphology is not well-explored. Here, we investigate assembly behavior of model divalent nanomonomers, DNA nanocuboid with tailorable multilinking bonds. Our study reveals that the characteristics of individual molecular linkages and their collective properties have a profound effect on nanomonomer reactivity and resulting morphologies. Beyond linear nanopolymers, a common signature of divalent nanomonomers, we observe an effective valence increase as linkages lengthened, leading to the nanopolymer bundling. The experimental findings are rationalized by molecular dynamics simulations. © 2021 The Authors. Published by American Chemical Society. This work was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, grant DE-SC0008772. This research used resources of the Center for Functional Nanomaterials and National Synchrotron Light Source II, supported by U.S. DOE Office of Science Facilities at Brookhaven National Laboratory under Contract No. DE-SC0012704. This research used imaging facilities of Advanced Science Research Center at City University of New York. D.M., P.A.S., and S.K. acknowledge support from the Austrian Research Fund (FWF), Project P33748. S.K. was also supported by the Russian Science Foundation Grant 19-12-00209 for computational work. Computer simulations were performed at the Vienna Scientific Cluster (VSC4).

The self-assembly of colloidal diamond (CD) crystals is considered as one of the most coveted goals of nanotechnology, both from the technological and fundamental points of view. For applications, colloidal diamond is a photonic crystal which can open new possibilities of manipulating light for information processing. From a fundamental point of view, its unique symmetry exacerbates a series of problems that are commonly faced during the self-assembly of target structures, such as the presence of kinetic traps and the formation of crystalline defects and alternative structures (polymorphs). Here we demonstrate that all these problems can be systematically addressed via SAT-assembly, a design framework that converts self-assembly into a satisfiability problem. Contrary to previous solutions (requiring four or more components), we prove that the assembly of the CD crystal only requires a binary mixture. Moreover, we use molecular dynamics simulations of a system composed by nearly a million nucleotides to test a DNA nanotechnology design that constitutes a promising candidate for experimental realization., 12 pages, 4 figures

Graphical abstract, Highlights • Biological networks are hard to study without simplified computational models. • Model polymers are shown to assemble into networks like those observed in biology. • Coarse-grained models allow simulation of a self assembly process over microseconds. • Metrics are developed to describe simulated networks and images of real networks. • Tangling in the model polymers is shown to influence the network structure., The properties of biological networks, such as those found in the ocular lens capsule, are difficult to study without simplified models. Model polymers are developed, inspired by “worm-like” curve models, that are shown to spontaneously self assemble to form networks similar to those observed experimentally in biological systems. These highly simplified coarse-grained models allow the self assembly process to be studied on near-realistic time-scales. Metrics are developed (using a polygon-based framework) which are useful for describing simulated networks and can also be applied to images of real networks. These metrics are used to show the range of control that the computational polymer model has over the networks, including the polygon structure and short range order. The structure of the simulated networks are compared to previous simulation work and microscope images of real networks. The network structure is shown to be a function of the interaction strengths, cooling rates and external pressure. In addition, “pre-tangled” network structures are introduced and shown to significantly influence the subsequent network structure. The network structures obtained fit into a region of the network landscape effectively inaccessible to random (entropically-driven) networks but which are occupied by experimentally-derived configurations.

The design and production of the next generations of synthetic aqueous self-Assembled systems able to mimic some biological features will require increasingly sophisticated monomer constituents that make use of additional interactions to hydrophibic effects to attain enhanced structural and functional complexity. Here, we broadly investigate the aqueous self-Assembly of dinucleobase amphiphilic monomers into helical nanotubes under a wide range of different conditions of temperature, concentration, solvent composition and pH. Such monomers comprise an amphiphilic π-conjugated central block, endowed with a lipophilic chiral tail and a hydrophilic group that can be made anionic (carboxylate), neutral (glycol) or cationic (ammonium), disubstituted with complementary guanine and cytosine nucleobases at each termini. These molecules self-Assemble into amphiphilic nanotubes in water but, when subjected to diverse (drastic) changes in the experimental conditions, undergo either disassembly into monomers, chiral reorganization, or a morphological restructuration into globular objects due to dehydration of the peripheral hydrophilic groups, Funding from the European Research Council (ERC-Starting Grant 279548 PROGRAM-NANO) and MINECO (CTQ2017- 84727-P) is gratefully acknowledged. F. A. is grateful to MSCA-COFUND InterTalentum (713366) and MSCA-IF (793506) programs. P. C. acknowledges the Comunidad de Madrid for the PEJ-2017-AI/IND-6246 contract

Hierarchical helicates based on ketone‐substituted titanium(IV)triscatecholates show different monomer‐dimer behavior depending on different solvents. The dimerization constants of a whole series of differently alkyl‐substituted complexes is analyzed to show that the solvent has a very strong influence on the dimerization. Hereby, effects like solvophobicity/philicity, sterics, electronics of the substituents and weak side‐chain—side‐chain interactions seem to act in concert., The behavior of the monomer–dimer equilibrium of hierarchical helicates formed from keto‐catechol ligands strongly depends on the solvent that is used. Based on the respective solvents, different side‐chain—side‐chain interaction modes such as sterics, solvophobicity/philicity and probably even London dispersion become highly influential for the stabilization or destabilization of the dimers.

N acylated substituted beta 3 oligoamides are known to form unique supramolecular nanorods based on a 3 point hydrogen bond self assembly motif. This motif is an intermolecular extension of the hydrogen bonding network that stabilizes the 14 helix secondary structure unique to beta 3 oligoamides. Acetylation of the N terminus of the molecule provides the necessary third hydrogen bond pair of the motif. Here, the possibility of introducing the third hydrogen bond pair via amidation of the C terminus is investigated. While similar in purpose, this modification introduces a chemically distinct new self assembly motif, also removing the bulky carboxyl group that does not fold into the 14 helix positioning instead as a side chain. Three substituted beta 3 oligoamide variants with the base sequence LIA where the letters denote beta 3 residues with side chains analogous to alpha amino acids were compared N acylated Ac beta 3 [LIA] as a reference, C amidated beta 3 [LIA] CONH2, and beta 3 [LIA] with free unmodified N and C termini as a negative control. The three variants were dissolved in water to promote self assembly. The self assembly was characterised using mid and far infrared spectroscopy, small angle x ray scattering SAXS and atomic force microscopy AFM . IR measurements confirmed that all three samples were in a similar conformation, consistent with pseudo 14 helical secondary structures. Far infrared spectroscopy measurements of beta 3 [LIA] CONH2 showed distinct peaks consistent with highly organised skeletal modes, i.e. regular supramolecular assembly, that was largely absent from the other two oligoamides. Modelling of SAXS data is consistent with elliptical cylinder structures resulting from nanorod bundling for both beta 3 [LIA] CONH2 and Ac beta 3 [LIA], but not in the unmodified sample. Consistently, AFM imaging showed large nanorod bundling structures in beta 3 [LIA] CONH2, varied bundling structures in Ac beta 3 [LIA], and only aggregation in beta 3 [LIA]. Amidation showed much more organised and robust assembly compared to acetylation, providing a new, easy to synthesize self assembly motif for helical nanorod assembly that is similar but distinct to N acylation

HYPOTHESIS: Despite advances in understanding the R5 (SSKKSGSYSGKSGSKRRIL) peptide-driven bio-silica process, there remains significant discrepancies regarding the physicochemical characterization and the self-assembling mechanistic driving forces of the supramolecular R5 template. This paper investigates the self-assembly of R5 as a function of monovalent (sodium chloride) and multivalent salt (phosphate) to determine if assembly is phosphate ion concentration dependent. Additionally, we hypothesize that the assembled R5 aggregates do not resemble a micelle or unimer structure as proposed in current literature.EXPERIMENTS: R5 peptides were synthesized, and aggregates evaluated for their size, morphology, and association state as a function of salt and ionic strength concentration via dynamic and static light scattering, small angle X-ray and neutron scattering and cryogenic transmission electron microscopy. Furthermore, we compare the proposed R5 template to precipitated silica by scanning electron microscopy.FINDINGS: R5 peptides assemble into large aggregates due to multivalence bridging and the decrease in electrostatic repulsion due to ionic strength. We elucidate the structure of R5 aggregates as mass-fractals composed of small spherical aggregates. Moreover, we discover that phosphate ions not only have a significant role in driving the growth of the R5 scaffold, but additionally in driving the polycondensation of silicic acid during the bio-silification process via electrostatic interactions.

The HIV-1 viral capsid is a conical-shaped protein shell consisting of approximately 1500 copies of a single capsid (CA) protein, arranged into a lattice of hexamers and precisely 12 pentamers. These pentamers form the vertices that result in the enclosed conical shape. The capsid encapsulates the viral genome and its associated replication machinery (known collectively as the capsid core), and has a functional role in almost every step of the early stage of the virus life cycle, including nuclear translocation, reverse transcription, and nuclear import, before undergoing controlled disassembly inside the nucleus to release the genomic content. The dynamics which control the coordinated behaviour of the capsid subunits are complex and not well understood, yet they remain critical to our understanding of the fundamental principles underlying viral self-assembly. Methods were established to create CA binding sites to specific regions of the DNA scaffolds to provide control over relative spatial positions of multiple subunits at low nanometre resolution. With this system, we were able to probe and measure CA inter-subunit binding kinetics for the first time using surface plasmon resonance. The approach provided sufficient sensitivity to measure extremely weak interactions between CA subunits via the intra-hexamer interface, and showed that binding of the sixth subunit within a hexamer may exhibit weak cooperativity. We also demonstrated that the inter-hexamer interface can be disrupted with a single point mutation. In addition, we structurally characterised the solution structure of the isolated CA hexamer using small-angle X-ray scattering and cryo-electron microscopy, which revealed close structural similarities with existing crystal structures and lattice-derived reconstructions of CA hexamers. We also used DNA scaffolds to assemble stable isolated hexamers without requiring salt-induced lattice assembly for the first time, and used this approach to attempt construction of a stable isolated CA pentamer in its native conformation. In this study, we present a new method for probing specific CA interactions within dimeric, hexameric and pentameric complexes, providing insight into the underlying kinetics of viral self-assembly. Furthermore, we demonstrate a bottom-up approach to assembly of stable CA structures using DNA nanostructures and discuss the potential of using DNA for assembling previously inaccessible, and larger capsid complexes.

International audience; Biocompatible materials are of paramount importance in numerous fields. Unlike chemically bridge polymer-based hydrogels, low-molecular-weight gelators can form a reversible hydrogel as their structures rely on noncovalent interaction. Although many applications with this type of hydrogel can be envisioned, we still lack their understanding due to the complexity of their self-assembly process and the difficulty in predicting their behaviors (transition temperature, gelation kinetics, the impact of solvent, etc.). In this study, we extend the investigations of a series of nucleosidederived gelators, which only differ by subtle chemical modifications. Using a multitechnique approach, we determined their thermodynamic and kinetic features on various scale (molecular to macro) in different conditions. Monitored at the supramolecular level by circular dichroism as well as macroscopic scales by rheology and turbidimetry, we found out that the sol-gel and gel-sol transitions are greatly dependent on the concentration and on the mechanisms that are probed. Self-assembly kinetics depends on hydrogel molecules and is modulated by temperature and solvent. This fundamental study provides insight on the impact of some parameters on the gelation process, such as concentration, cooling rate, and the nature of the solvent.

Excited states in organic semiconductors are generated, transported, and converted through ��-orbital interactions between multiple molecules. Hence, efficiency depends on the relative geometries between molecules. Yet, control over spatial assembly of organic semiconductors is challenging. Large aromatic molecules will self-assemble into extended structures with no size or positional control. Deterministic interactions between two different semiconductor molecules is even rarer. In contrast, selective and high-yielding DNA base pairing interactions can control discrete, self-assembly of nanoscale structures. After introducing relevant synthetic and theoretical background to DNA assembly and interchromophore coupling, the synthesis of DNA-conjugated organic semiconductors are described. Semiconductors were inserted into the phosphodiester backbone of DNA, maintaining DNA���s self-assembling properties. The appended DNA direct the interactions between predefined numbers of the same molecule, followed by hetero-assemblies composed of different molecular backbones. DNA-directed changes are interrogated by excitonic couplings, using steady-state time-resolved optical spectroscopy to track the excited state evolution. Homo-aggregate molecules exhibit excitonic coupling. In contrast, heterostacks were capable of charge transfer between an electron-donor and electron-acceptor on DNA. Finally, singlet-fission active molecules were attached to DNA. This process generates two triplet excitons from one singlet exciton. The evolution of this process was tracked using time-resolved optical and magnetic spectroscopy. The combined observations in this thesis show multi-chromophore dependent phenomena are replicated in the aqueous DNA environment. Importantly, DNA successfully restricts and controls the extent of chromophore interaction to produce size-dependent phenomena and impart spatial control of multiple, different semiconductors.

One of the fundamental goals of nanotechnology is to exploit selective and directional interactions between molecules to design particles that self-assemble into desired structures, from capsids, to nano-clusters, to fully formed crystals with target properties (e.g. optical, mechanical, etc.). Here we provide a general framework which transforms the inverse problem of self-assembly of colloidal crystals into a Boolean satisfiability problem for which solutions can be found numerically. Given a reference structure and the desired number of components, our approach produces designs for which the target structure is an energy minimum, and also allows to exclude solutions that correspond to competing structures. We demonstrate the effectiveness of our approach by designing model particles that spontaneously nucleate milestone structures such as the cubic diamond, the pyrochlore and the clathrate lattices., Comment: 12 pages, 3 figures

Control on microscopic scales depends critically on our ability to manipulate interactions with different physical fields. The creation of micro-machines therefore requires us to understand how multiple fields, such as surface capillary or electro-magnetic fields, can be used to produce predictable behaviour. Recently, a spinning micro-raft system was developed that exhibited both static and dynamic self-assembly [Wang et al., Sci. Adv., 2017, 3, e1602522]. These rafts employed both capillary and magnetic interactions and, at a critical driving frequency, would suddenly change from stable orbital patterns to static assembled structures. In this paper, we explain the dynamics of two interacting micro-rafts through a combination of theoretical models and experiments. This is first achieved by identifying the governing physics of the orbital patterns, the assembled structures, and the collapse separately. We find that the orbital patterns are determined by the short range capillary interactions between the disks, while the explanations of the other two behaviours only require the capillary far field. Finally we combine the three models to explain the dynamics of a new micro-raft experiment., European Union (European Union); European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme; Max Planck Society; Alexander von Humboldt Foundation

Conventional heat treatments to generate well-ordered and crystalline mesoporous oxide and carbon structures are limited by long durations and annealing temperatures that can cause mesostructural collapse. This paper describes a facile strategy coupling block copolymer-directed self-assembly with high-power Joule heating to form highly crystalline and well-ordered mesoporous oxide and carbon nanostructures within second timeframes. The combined approach is compatible with various functional self-assembled hybrid systems with a range of crystallization temperatures, generating mesoporous composites of γ-Al2O3-carbon, γ-Al2O3/MgO-carbon, and anatase-TiO2-carbon with p6mm symmetry, non-close-packed mesoporous carbon, as well as hierarchical mesoporous α-Fe2O3-carbon structures. Removing the polymer/carbon gives well-defined, highly crystalline mesoporous all-γ-Al2O3 and all-anatase-TiO2 structures. Impregnation of chloroplatinic acid followed by Joule heating yields platinum nanoparticles decorated on the channel walls of mesoporous γ-Al2O3-carbon structures. The resultant Joule-heating-induced well-ordered crystalline mesoporous oxide and oxide-carbon structures have high thermal and structural stabilities and exhibit better performances in CO2 adsorption capacity and lithium-ion batteries than conventional heat-treated counterparts. This approach represents an energy-efficient and time-saving route toward ordered porous materials with high surface area and pore accessibility for a wide range of environmental applications such as carbon sequestration, renewable energy storage, and environmental filtration. Nanyang Technological University National Research Foundation (NRF) Submitted/Accepted version This work was supported by a member-directed research grant from ExxonMobil through the Singapore Energy Center (EM11161.TO6) and a startup grant from Nanyang Technological University, Singapore. S.M. and W.M.Jr. wish to acknowledge financial support from the National Research Foundation of Singapore (NRF) Investigatorship Award (NRFI 2017-08).

Halogenated aromatic molecules assemble on surfaces forming both hydrogen and halogen bonds. Even though these systems have been intensively studied on flat metal surfaces, high-index vicinal surfaces remain challenging, as they may induce complex adsorbate structures. The adsorption of 2,6-dibromoanthraquinone (2,6-DBAQ) on flat and stepped gold surfaces is studied by means of van der Waals corrected density functional theory. Equilibrium geometries and corresponding adsorption energies are systematically investigated for various different adsorption configurations.~It is shown that bridge sites and step edges are the preferred adsorption sites for single molecules on flat and stepped surfaces, respectively. The role of van der Waals interactions, halogen bonds and hydrogen bonds are explored for a monolayer coverage of 2,6-DBAQ molecules, revealing that molecular flexibility and intermolecular interactions stabilize two-dimensional networks on both flat and stepped surfaces. Our results provide a rationale for experimental observation of molecular carpeting on high-index vicinal surfaces of transition metals., Comment: Preprint. 24 pages, 5 figures

Arslan Yildiz, Ahu/0000-0003-0348-0575, WOS: 000427539200003, The magnetic levitation technique has been utilized to orientate and manipulate objects both in two dimensions (2D) and three dimensions (3D) to form complex structures by combining various types of materials. Magnetic manipulation holds great promise for several applications such as self-assembly of soft substances and biological building blocks, manipulated tissue engineering, as well as cell or biological molecule sorting for diagnostic purposes. Recent studies are proving the potential of magnetic levitation as an emerging tool in biotechnology. This review outlines the advances of newly developing magnetic levitation technology on biological applications in aqueous environment from the biotechnology perspective.

One of the major challenges in modern robotics is controlling micromanipulation by active and adaptive materials. In the respiratory system, such actuation enables pathogen clearance by means of motile cilia. While various types of artificial cilia have been engineered recently, they often involve complex manufacturing protocols and focus on transporting liquids only. Here, soft magnetic carpets are created via an easy self-assembly route based on the Rosensweig instability. These carpets can transport not only liquids but also solid objects that are larger and heavier than the artificial cilia, using a crowd-surfing effect.This amphibious transportation is locally and reconfigurably tunable by simple micromagnets or advanced programmable magnetic fields with a high degree of spatial resolution. Two surprising cargo reversal effects are identified and modeled due to collective ciliary motion and nontrivial elastohydrodynamics. While the active carpets are generally applicable to integrated control systems for transport, mixing, and sorting, these effects can also be exploited for microfluidic viscosimetry and elastometry., Advanced Science, 8 (21), ISSN:2198-3844

We studied how changing the anion affects the self-assembly of three diimidazolium salts bearing a perylene bisimide spacer. In particular we used [BF 4 − ] and [NTf 2 − ] based salts together with a mixed salt bearing both [I − ] and [BF 4 − ] anions. Thermal as well as concentration and temperature dependent spectroscopic investigations revealed that changing the anion impacts on solid state and solution aggregation, leading to articulate thermotropic behaviors and contrasting solvent effects, respectively. We also studied the electrochemical behavior of the salts to verify if changing the anion alters the redox properties of the salts. Finally, different anions also lead to very different aggregate morphologies, as evidenced by SEM and TEM measurements.

Using computer simulations and a mean-field theoretical approach, we study how the growth in dipolar interparticle correlations manifests itself in the frequency-dependent initial magnetic susceptibility of a ferrofluid. Our recently developed theory gives the correct single-particle Debye-theory results in the low-concentration, non-interacting regime; and it yields the exact leading-order contributions from interparticle correlations. The susceptibility spectra are analysed in terms of the low-frequency behaviours of the real and imaginary parts, and the position of the peak in the imaginary part. By comparing the theoretical predictions to the results from Brownian dynamics simulations, it is possible to identify the conditions where correlations are important, but where self-assembly has not developed. We also provide a qualitative explanation for the behaviour of spectra beyond the mean-field limit. © 2016 Elsevier B.V.

Well-defined poly(N-vinylcaprolactam-co-vinyl acetate) thermoresponsive particles physically crosslinked by means of hydrophobic interactions were synthesized by polymerization-induced self-assembly. It was highlighted that a xanthate-terminated poly(ethylene glycol) (PEG-X) efficiently acted as both a stabilizer and a macromolecular chain transfer agent for the RAFT/MADIX batch emulsion copolymerization of N-vinylcaprolactam (VCL) and vinyl acetate (VAc), enabling the direct synthesis in aqueous dispersed media of PEG-b-P(VAc-co-VCL) block copolymers. It was emphasized that a fraction of 47 mol% of hydrophobic VAc in the second block of the copolymer was suitable for maintaining the integrity of the self-assembled PEG-b-P(VAc-co-VCL) block copolymer particles at low temperature while exhibiting a temperature-induced phase transition. The well-defined physically crosslinked particles interestingly behaved as thermoresponsive colloids analogous to chemically crosslinked microgels. The PEG-b-P(VAc0.47-co-VCL0.53) particles were able to undergo a reversible swollen-to-collapse transition with increasing temperature in the absence of hysteresis. The PEG-b-P(VAc0.17-co-VCL0.83) block copolymer with a lower fraction of VAc in the copolymer (17 mol%) behaved oppositely as very small objects were present in the aqueous phase at low temperature (T < 20 °C) and self-assembled into large aggregates by increasing the temperature. Finally, the statistical copolymers based on VAc and VCL were successfully hydrolyzed into promising thermoresponsive biocompatible statistical copolymers based on vinyl alcohol and N-vinylcaprolactam co-monomer units.

We propose a new method to produce fluorinated nanoparticles (NPs) based on ab initio reversible addition-fragmentation chain transfer (RAFT) emulsion polymerization without the use of toxic surfactants. NP size, surface charge, and chemistry can be controlled via the adoption of different macromolecular transfer agents produced via RAFT polymerization of amphiphilic monomers. Thanks to this versatility, interparticle interactions can be easily tuned by changing solvent composition and temperature. In addition, the refractive index and density of the solvent can simultaneously match those of the NPs by adding sodium polytungstate, an organic salt widely used for density gradient centrifugation. These colloids may be used as model systems for the study of self-assembly and aggregation in aqueous media when optical methods are required.

Testing the hearing abilities of marine mammals under water is a challenging task. Sample sizes are usually low, thus limiting the ability to generalize findings of susceptibility towards noise influences. A method to measure harbor porpoise hearing thresholds in situ in outdoor conditions using auditory steady state responses of the brainstem was developed and tested. The method was used on 15 live-stranded animals from the North Sea during rehabilitation, shortly before release into the wild, and on 12 wild animals incidentally caught in pound nets in Denmark (inner Danish waters). Results indicated that although the variability between individuals is wide, the shape of the hearing curve is generally similar to previously published results from behavioral trials. Using 10-kHz frequency intervals between 10 and 160 kHz, best hearing was found between 120 and 130 kHz. Additional testing using one-third octave frequency intervals (from 16 to 160 kHz) allowed for a much faster hearing assessment, but eliminated the fine scale threshold characteristics. For further investigations, the method will be used to better understand the factors influencing sensitivity differences across individuals and to establish population-level parameters describing hearing abilities of harbor porpoises.

Porous polymers have immense potential in catalysis, energy conversion and storage, separation sciences and life sciences due to their high surface area and high diffusion flux. Developing porous polymers with micro and mesoscale porosity with long-range order is challenging and involves multistep templated approaches. Here we demonstrate a simple surface-oxygen induced electropolymerization route to directly obtain self-assembled porous polymers of polyparaphenylene (PPP) and PPP based copolymers in ionic liquids. By combining experimental and theoretical studies, we show that surface oxygen on Cu changes the orientation and assembly of benzene which then results in a change in electropolymerization mechanism leading to a self-assembled porous structure with porosity between 2 and 5 μm. Furthermore, with controlled experimental parameters, bicontinuous conducting polymers with porosity of >10 μm are obtained. The porous conducting polymers show absorption of light in the visible range which was also used as an efficient electrode for investigation of the photoelectrochemical oxygen evolution reaction. We acknowledge the use of Athena at HPC Midlands+ in this research, which was funded by the EPSRC (grant EP/P020232/1) via the EPSRC RAP call of spring 2018 and 2019. Supercomputer Wales is also thanked for the computing time. In this work ARCHER - the UK National Supercomputing Service (https://www.archer.ac.uk) was also used via the membership of the UK’s HEC Materials Chemistry Consortium, which is funded by EPSRC (EP/L000202).

The Type III Secretion System (T3SS) is a protein superstructure, consisting of hundreds of subunits, which self-assemble into a molecular needle and syringe that allows bacteria to inject effector proteins directly into eukaryotic host cells. These effector proteins promote virulence in many pathogenic bacteria. The extracellular needle filament is capped by a pentameric tip complex that is involved in environmental sensing and regulation of a pore-forming complex that is secreted upon host-cell contact. Tip complexes do not self-assemble from in vitro solutions of their subunits alone suggesting that in vivo, other environmental factors are required. During in vivo assembly, each tip complex subunit unfolds within the bacteria and secrets through the needle filament whereupon they refold and localize to the filaments end. We attempt to recapitulate these conditions in vitro. The influence of unfolding and refolding on tip complex assembly was investigated using pH and temperature denaturation combined with small angle X-ray scattering (SAXS). This data confirmed that in vitro refolding can promote oligomer formation in some species but is an inefficient process. To test the effects of needle localisation we developed a novel DNA-templating approach. Nanoscale DNA templates with the same dimensions of the needle filament (~8 nm) were designed, synthesised, and measured with electron microscopy, molecular dynamics simulations, and SAXS. Tip complex subunits were then chemically localized to these DNA templates drastically increasing their relative concentration and interaction frequency. Electron micrographs of these DNA-templated assemblies revealed some particles with compact structures similar to those observed in vivo. Chemical cross-linking and mass-spectroscopy provided distance restraints between residues of subunits in DNA-templated assemblies. These restraints allowed the generation of rigid body models of DNA-templated assemblies that resemble current models of in vitro tip complexes. These results present a promising future for the ability to rationally control protein assembly of difficult to access structures using the DNA-templating approach developed here.

12 pags., 8 figs., 1 tab., Substance P (SP) is one of the most studied peptide hormones and knowing the relationship between its structure and function may have important therapeutic applications in the treatment of a variety of stress-related illnesses. In order to obtain a deeper insight into its folding, the effects of different factors, such as pH changes, the presence of Ca ions, and the substitution of the Met-NH moiety in the SP structure, was studied by Raman and infrared spectroscopies. SP has a pH-dependent structure. Under acidic–neutral conditions, SP possesses a prevalent β-sheet structure although also other secondary structure elements are present. By increasing pH, a higher orderliness in the SP secondary structure is induced, as well as the formation of strongly bound intermolecular β-strands with a parallel alignment, which favour the self-assembly of SP in β-aggregates. The substitution of the Met-NH moiety with the acidic functional group in the SP sequence, giving rise to a not biologically active SP analogue, results in a more disordered folding, where the predominant contribution comes from a random coil. Conversely, the presence of Ca ions affects slightly but sensitively the folding of the polypeptide chain, by favouring the α-helical content and a different alignment of β-strands; these are structural elements, which may favour the SP biological activity. In addition, the capability of SERS spectroscopy to detect SP in its biologically active form was also tested by using different metal nanoparticles. Thanks to the use of silver NPs prepared by reduction of silver nitrate with hydroxylamine hydrochloride, SP can be detected at very low peptide concentration (~ 90 nM). However, the SERS spectra cannot be obtained under alkaline conditions since both the formation of SP aggregates and the lack of ion pairs do not allow a strong enough interaction of SP with silver NPs. [Figure not available: see fulltext.]., This work was supported by the Scientific Grant Agency of the Ministry of the Education of Slovak Republic (APVV-15- 0485) and the Ministerio de Economía y Competitividad from Spain under the grant FIS2017-84314-R.

Self-assembly structured Sm2O3 nanomaterials were prepared by a simple and cost effective hydrothermal method and subsequent annealing at 800 °C in air. The size, shape and phase composition of the structures synthesized by changing the hydrothermal processing time were characterized by SEM-EDX, XRD, micro-Raman and photoluminescence (PL) analysis. Differences in particle aggregation and coalescence were reported upon varying the timing of hydrothermal process (from 24 to 36 h). Sensors performances of the synthesized Sm2O3 nanostructures have been investigated for the monitoring of two important volatile organic compounds (VOCs) such as ethanol and acetone.

Photonic technology is widely based on anisotropic (and) nonlinear materials, which allow light modulation and parametric light conversion. Because the number of naturally occurring crystals is limited, there is a growing demand for artificial metamaterials with optical properties specifically tailored to a given application. Here, we utilize the top-down method to synthesize sub-wavelength periodic nanostructures inside a uniaxial optically nonlinear crystal (lithium niobate, LiNbO₃) by irradiating it with multiple femtosecond laser pulses. By superimposing form-birefringence associated with the light-induced nanostructures onto natural birefringence of the host crystal we create macroscopic domains of a biaxial metamaterial embedded into otherwise uniaxial medium.

As an extension of our studies on the multifaceted properties of C-alkylated resorc[4]arenes, we planned to immobilize on a solid support resorc[4]arenes with C11-long side chains in the lower rim. To this purpose, we synthesized two conformationally diverse resorc[4]arenes containing a bromoundecyl moiety in the four axial pendants. The cone stereoisomer 6a (30% yield) was selected for the reaction with an aminopropylated silica gel (APSG) obtained from spherical Kromasil Si 100, 5 μm particles, to give the corresponding immobilized SP-C11-resorc[4]arene system. The resulting polar-embedded stationary phase was fully characterized and investigated in the HPLC discrimination of the E/Z stereoisomers of naturally occurring and semisynthetic combretastatins, a family of (Z)-stilbene anticancer drugs. The chair stereoisomer 6b (20% yield), when submitted to X-ray diffraction analysis, showed a noteworthy self-assembly in the crystal lattice, with intercalated hydrophobic and polar layers as a result of inter...

Terminally unsaturated and diastereochemically pure polyol derived from d-mannose shows spontaneous aggregation behavior in water solution. In order to study and clarify this unforeseen phenomenon, a conformational study based on NMR spectroscopy combined with ab initio structure analysis using the COSMO-solvation model was pursued. The results, together with X-ray diffraction studies, suggest a low energy linear conformation for this particular substrate both in solid states and in solution. For such small-sized acyclic carbohydrate derivatives, the linear conformation appears to be a key prerequisite for the unusual molecular self-assembly reported herein. peerReviewed

International audience; Soft mesoporous hierarchically structured particles were created by the self-assembly of an amphiphilic deep cavitand cyclodextrin βCD-nC10 (degree of substitution n = 7.3), with a nanocavity grafted by multiple alkyl (C10) chains on the secondary face of the βCD macrocycle through enzymatic biotransesterification, and the nonlamellar lipid monoolein (MO). The effect of the non-ionic dispersing agent polysorbate 80 (P80) on the liquid crystalline organization of the nanocarriers and their stability was studied in the context of vesicle-to-cubosome transition. The coexistence of small vesicular and nanosponge membrane objects with bigger nanoparticles with inner multicompartment cubic lattice structures was established as a typical feature of the employed dispersion process. The cryogenic transmission electron microscopy (cryo-TEM) images and small-angle X-ray scattering (SAXS) structural analyses revealed the dependence of the internal organization of the self-assembled nanoparticles on the presence of embedded βCD-nC10 deep cavitands in the lipid bilayers. The obtained results indicated that the incorporated amphiphilic βCD-nC10 building blocks stabilize the cubic lattice packing in the lipid membrane particles, which displayed structural features beyond the traditional CD nanosponges. UV-Vis spectroscopy was employed to characterize the nanoencapsulation of a model hydrophobic dimethylphenylazo-naphthol guest compound (Oil red) in the created nanocarriers. In perspective, these dual porosity carriers should be suitable for co-encapsulation and sustained delivery of peptide, protein or siRNA biopharmaceuticals together with small molecular weight drug compounds or imaging agents. © 2016 The Royal Society of Chemistry.

The endohedral metallofullerene (EMF) self-assembly process in Sc/carbon vapor in the presence and absence of an inert cooling gas (helium) is systematically investigated using quantum chemical molecular dynamics simulations. It is revealed that the presence of He atoms accelerates the formation of pentagons and hexagons and reduces the size of the self-assembled carbon cages in comparison with analogous He-free simulations. As a result, the Sc/C/He system simulations produce a larger number of successful trajectories (i.e. leading to Sc-EMFs) with more realistic cage-size distribution than simulations of the Sc/C system. The main Sc encapsulation mechanism involves nucleation of several hexagons and pentagons with Sc atoms already at the early stages of carbon vapor condensation. In such proto-cages, both Sc–C σ-bonds and coordination bonds between Sc atoms and the π-system of the carbon network are present. Sc atoms are thus rather labile and can move along the carbon network, but the overall bonding is sufficiently strong to prevent dissociation even at temperatures around 2000 kelvin. Further growth of the fullerene cage results in the encapsulation of one or two Sc atoms within the fullerene. In agreement with experimental studies, an extension of the simulations to Fe and Ti as the metal component showed that Fe-EMFs are not formed at all, whereas Ti is prone to form Ti-EMFs with small cage sizes, including Ti@C28-Td and Ti@C30-C2v(3).

The development and availability of new protecting groups are vital for all branches of synthetic chemistry. Equally vital is the facile and selective removal of these groups, leaving intact other protecting groups which are to be cleaved later. Herein we demonstrate this concept of orthogonal deprotection by combining three different forms of protected methacrylic acid (MAA) in the same terpolymers. One of these protected monomers was 2-(pyridin-2-yl)ethyl methacrylate (PyEMA), recently developed by us, whose units can be readily converted to MAA units either under alkaline hydrolysis conditions or thermally. The second monomer was tetrahydro-2H-pyran-2-yl methacrylate (THPMA) which can be cleaved either via acidic hydrolysis or by thermolysis. The third form of protected MAA was benzyl methacrylate (BzMA) which can be subjected to hydrogenolysis. Two ABC triblock terpolymers based on all three of these monomers were successfully synthesized-one by reversible addition-fragmentation chain transfer (RAFT) polymerization and the other by group transfer polymerization (GTP)-thus proving the feasibility of these demanding three-stage syntheses via both polymerization methods. The molecular weight characteristics and compositions of the terpolymers were determined by gel permeation chromatography and proton nuclear magnetic resonance spectroscopy (1H NMR), respectively. Subsequently, the ABC triblock terpolymers were sequentially subjected to conditions of alkaline hydrolysis, acidic hydrolysis, and hydrogenolysis, leading to the selective cleavage of the PyEMA, the THPMA and the BzMA units, respectively, without affecting the remaining types of protecting groups, according to analysis using 1H NMR spectroscopy. Similarly selective was the acidic hydrolysis followed by alkaline hydrolysis. Thermal treatment at 130 °C of the terpolymers led to the conversion of both the PyEMA and the THPMA units to MAA units, without affecting the BzMA units, yielding amphiphilic diblock copolymers whose self-assembly properties in water were investigated. © 2015 American Chemical Society. 48 20 7503 7512 Cited By :8

We propose a microfluidic system that generates nanovesicles (NVs) by slicing living cell membrane with microfabricated 500 nm-thick silicon nitride (SixNy) blades. Living cells were sliced by the blades while flowing through microchannels lined with the blades. Plasma membrane fragments sliced from the cells self-assembled into spherical NVs of ∼100–300 nm in diameter. During self-assembly, the plasma membrane fragments enveloped exogenous materials (here, polystyrene latex beads) from the buffer solution. About 30% of beads were encapsulated in NVs, and the generated NVs delivered the encapsulated beads across the plasma membrane of recipient cells, but bare beads could not penetrate the plasma membrane of recipient cells. This result implicates that the NVs generated using the method in this study can encapsulate and deliver exogenous materials to recipient cells, whereas exosomes secreted by cells can deliver only endogenous cellular materials.

Aggregation-induced quenching is particularly detrimental in perylene diimides, which are characterized by a near-unity fluorescence quantum yield in solution but are far less emissive in the solid state. Previously, perylene diimide has been improved by linking it to the inorganic cage of polyhedral oligomeric silsesquioxanes. As a further study on perylene diimidepolyhedral oligomeric silsesquioxanes, we report on a double functionalized molecular structure, which can be used for substitution at the bay area and as a side group in other materials. Typical solution absorption and emission features of the perylene diimide fragment have been observed in this new reactive perylene diimide-polyhedral oligomeric silsesquioxane. Moreover, reduced stacking during aggregation and spherical particles exhibiting solid fluorescence have been obtained. Organic semiconducting material with enhanced solid state photophysical properties, like solid fluorescence is a subject of great interest owing to its possible high-tech applications in optoelectronic devices.

We study self-assembly in suspensions of supracolloidal polymer-like structures made of crosslinked magnetic particles. Inspired by self-assembly motifs observed for dipolar hard spheres, we focus on four different topologies of the polymer-like structures: linear chains, rings, Y-shaped and X-shaped polymers. We show how the presence of the crosslinkers, the number of beads in the polymer and the magnetic interparticle interaction affect the structure of the suspension. It turns out that for the same set of parameters, the rings are the least active in assembling larger structures, whereas the system of Y- and especially X-like magnetic polymers tends to form very large loose aggregates. © 2018 Elsevier B.V.

Self-assembled molecular triangles [Pd3(phen)3(imidazolate)3](NO3)3, 1a and [Pd3(phen)3 (imidazolate)3](PF6)3, 1b are prepared by the combination of imidazole with Pd(phen)(NO3)2 and Pd(phen) (PF6)2, respectively. Imidazole was deprotonated during the complexation reactions and the imidazolate so formed acted as a bis-monodentate bridging ligand to form the bowl-shaped trinuclear architectures of 1a/b. Relative orientation of the imidazolate moieties can be best described as syn,anti,antias observed in the crystal structure of 1b. However, in solution state, slow conformational changes are assumed on the basis of 1HNMR spectral data. The molecular triangles are crafted with three peripheral phen units capable of ?-? stacking interactions. Well-fashioned intermolecular ?-? interactions are observed in the solid-state, wherein further self-assembly of already self-assembled triangle is observed. � 2015 Indian Academy of Sciences.

Perpendicularly oriented lamellar forming block copolymers are promising candidates for the fabrication of high aspect ratio nanostructures either by means of direct pattern transfer to the underlying substrate or by sequential infiltration processes. In this work, highly ordered lamellar grains (? > 500 nm) were produced by thermally treating the samples at high temperature (Ttarget > 250 °C) in a Rapid Thermal Processing (RTP) machine. The variation of the lateral order of the nanostructures during the annealing process was investigated in detail, by decoupling the effect of the transients and of the isothermal step of the thermal treatment. Moreover, the self-assembly process was studied as a function of the annealing time and temperature in order to identify the processing parameters that maximize the lateral order avoiding, and at the same time, any degradation of the macromolecules. From this study the activation energy (Ea ~ 55 kJ mol-1) of the lamellar grain coarsening process on featureless substrates was determined. The specific process conditions that promote the self-assembly of lamellar thin films reaching a level of lateral order that is suitable for nanostructure fabrication were established.

Hexaazamacrocycle (L) stabilized gold nanoparticles (AuNPs) were prepared by combining L with HAuCl4�3H2O in a variety of alcohol-water (1:1) mixtures. The dual roles of L as a reducing and stabilizing agent were exploited for the synthesis of AuNPs under the optimized ratio of L to Au3+ (2:1). Self-assembled gold nanofilms (AuNFs) were constructed at liquid-liquid interfaces by adding equal volumes of hexane to the dispersions of AuNPs in the alcohol-water systems. The nanofilms were formed spontaneously by shaking the two-phase mixture for a minute followed by standing. The alcohols explored for the self-assembly phenomenon were methanol, ethanol, i-propanol and t-butanol. The systems containing methanol or t-butanol resulted in AuNFs at the interfaces, whereas the other two alcohols were found not suitable and the AuNPs remained dispersed in the corresponding alcohol-water medium. The AuNFs prepared under suitable conditions were coated on a variety of surfaces by the dip and lift-off method/solvent removal approach. The AuNFs were characterized by UV-vis, SEM, TEM, AFM and contact angle measurement techniques. A coated glass-vial or cuvette was used as a catalytic reservoir for nitro-reduction reactions under ambient and aqueous conditions using NaBH4 as the reducing agent. The reduced products (amines) were extracted by aqueous work-up using ethyl acetate followed by evaporation of the organic layer, the isolated products required no further purification. The catalyst was recovered by simply decanting the reaction mixture whereupon the isolated catalyst remained coated inside the vessel. The recovered catalyst was found to be equally efficient for further catalytic cycles. � 2015 The Royal Society of Chemistry.

'Directing' block copolymer (BCP) patterns is a possible option for future semiconductor device patterning, but pattern transfer of BCP masks is somewhat hindered by the inherently low etch contrast between blocks. Here, we demonstrate a 'fab' friendly methodology for forming well-registered and aligned silicon (Si) nanofins following pattern transfer of robust metal oxide nanowire masks through the directed self-assembly (DSA) of BCPs. A cylindrical forming poly(styrene)-block-poly(4-vinyl-pyridine) (PS-b-P4VP) BCP was employed producing 'fingerprint' line patterns over macroscopic areas following solvent vapor annealing treatment. The directed assembly of PS-b-P4VP line patterns was enabled by electron-beam lithographically defined hydrogen silsequioxane (HSQ) gratings. We developed metal oxide nanowire features using PS-b-P4VP structures which facilitated high quality pattern transfer to the underlying Si substrate. This work highlights the precision at which long range ordered [similar]10 nm Si nanofin features with 32 nm pitch can be defined using a cylindrical BCP system for nanolithography application. The results show promise for future nanocircuitry fabrication to access sub-16 nm critical dimensions using cylindrical systems as surface interfaces are easier to tailor than lamellar systems. Additionally, the work helps to demonstrate the extension of these methods to a 'high [small chi]' BCP beyond the size limitations of the more well-studied PS-b-poly(methyl methylacrylate) (PS-b-PMMA) system.

In order to expand the application of bio-derived polymers it is imperative that the issues related to their poor gas barrier properties be addressed. Here we explore the sequential layer by layer electrostatic self-assembly approach (abbrev. LbL) for modifying the oxygen transmission rate (OTR) of biopolyesters with the trademark – FF 1482® (abbrev. BP) by deposition of fish gelatin/natural montmorillonite clay (trademark – Cloisite Na+, abbrev. CloNa+). We will show that the deposition of fish gelatin/CloNa+ onto the BP surface is influenced by different process parameters such as dipping time, drying step, polyelectrolyte concentration and surface activation of the BP film via partial alkaline hydrolysis as well as via low pressure plasma. Micro-attenuated total reflectance Fourier-transform infrared spectroscopy (mATR-FTIR) and scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) showed that the traditional dipping LbL technique, which involves keeping the film wet throughout all deposition cycles, led to a heterogeneous multilayered structure. The addition of the drying step has proven to be a crucial parameter to obtain a quite homogenous fish gelatin/CloNa+ multi-layered structure. Further, the homogeneity of the multi-layered structure was considerable improved when both the CloNa+ concentration was increased and the BP film surface was activated. By exploiting these processing parameters we were able to achieve successful homogenous fish gelatin/CloNa+ multi-layered structures as shown by SEM/EDS analysis. Further, the optimised samples showed a drastic decrease in OTR. For example, the OTR value for the sample, in which the BP surface was activated via plasma treatment prior to deposition of fish gelatin/CloNa+, was reduced by 97% of the corresponding value of untreated BP film. This remarkable barrier may be attributed to a greater dispersion of the impermeable inorganic CloNa+ platelets which forces the oxygen molecules to diffuse around them rather than take a straight line pathway that lies perpendicular to the film surface. Thus, this results is a long and tortuous pathway for oxygen molecule diffusion through the multilayered structures.

Controlling the hierarchical organization of self-assembling peptide amphiphiles into supramolecular nanostructures opens up the possibility of developing biocompatible functional supramolecular materials for various applications. In this study, we show that the hierarchical self-assembly of histidine- (His-) functionalized PAs containing d- or l-amino acids can be controlled by both solution pH and molecular chirality of the building blocks. An increase in solution pH resulted in the structural transition of the His-functionalized chiral PA assemblies from nanosheets to completely closed nanotubes through an enhanced hydrogen-bonding capacity and π-π stacking of imidazole ring. The effects of the stereochemistry and amino acid sequence of the PA backbone on the supramolecular organization were also analyzed by CD, TEM, SAXS, and molecular dynamics simulations. In addition, an investigation of chiral mixtures revealed the differences between the hydrogen-bonding capacities and noncovalent interactions of PAs with d- and l-amino acids.

This paper presents a new model for polymersomes developed using a poly(ethylene oxide)-poly(butadiene) diblock copolymer bilayer. The model is based on a coarse-grained approach using the MARTINI force field. Since no MARTINI parameters exist for poly(butadiene), we have refined these parameters using quantum mechanical calculations and molecular dynamics simulations. The model has been validated using extensive molecular dynamics simulations in systems with several hundred polymer units and reaching up to 6 μs. These simulations show that the copolymer coarse grain model self-assemble into bilayers and that NPT and NPNγT ensemble runs reproduce key structural and mechanical experimental properties for different copolymer length chains with a similar hydrophilic weight fraction. Fil: Grillo, Damián Alexis. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; Argentina Fil: Albano, Juan Manuel Ricardo. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentina Fil: Mocskos, Esteban Eduardo. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Computación; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Centro de Simulación Computacional para Aplicaciones Tecnológicas; Argentina Fil: Facelli, Julio C.. University of Utah; Estados Unidos Fil: Pickholz, Mónica Andrea. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentina Fil: Ferraro, Marta Beatriz. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentina

An 2-ureido-4[1H]pyrimidinone (UPy) motif with self-association capability (through quadruple hydrogen bonds) was successfully anchored onto montmorillonite clay layers. Polymer/clay nanocomposites were prepared by specific hydrogen bonding interactions between surface functionalized silica nanoclays and UPy-bonded supramolecular poly(ethylene glycol) or poly(ɛ-caprolactone). The mixed morphologies including intercalated layers with a non-uniform separation and exfoliated single layers isolated from any stack were determined by combined X-ray diffraction and transmission electron microscopic measurements. Thermal analyses showed that all nanocomposites had higher decomposition temperatures and thermal stabilities compared with neat polymer. The differential scanning calorimetric data implied that the crystallinity of polymers did not show essential changes upon introduction of organomodified UPy clays. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 650–658

We describe the synthesis and self-assembly of particularly high periodicity of diblock copolymers composed of poly(benzyl-l-hydroxyproline) (PBLHyP) and poly(γ-benzyl-l-glutamate) (PBLG), that is, two polypeptide blocks with dissimilar helical structures. The robust helicity of the PBLHyP block is driven by steric constraints of the repeat units, while PBLG forms α-helices driven by hydrogen bonding, allowing defects and deformations. Herein, high-molecular-weight diblock copolypeptides of PBLG-b-PBLHyP with three different volume fractions of the PBLHyP-blocks are discussed. For shorter PBLHyP blocks, hexagonal packing of PBLHyP helices is observed, while by increasing the length of the PBLHyP block, keeping at a similar PBLG block length, the packing is distorted. Zig-zag lamellar structures were obtained due to the mismatch in the packing periodicities of the PBLG and PBLHyP helices. The frustration that takes place at the interface leads the PBLHyP to tilt to match the PBLG periodicity. The zig-zag morphology is reported for the first time for high-molecular-weight helix-helix (rod-rod) copolypeptides, and the self-assembled periodicity is uncommonly large.

The molecular imprinting technique depends on the molecular recognition. It is a polymerization method around the target molecule. Hence, this technique creates specific cavities in the cross-linked polymeric matrices. In present study, a sensitive imprinted electrochemical biosensor based on Fe@Au nanoparticles (Fe@AuNPs) involved in 2-aminoethanethiol (2-AET) functionalized multi-walled carbon nanotubes (f-MWCNs) modified glassy carbon (GC) electrode was developed for determination of cefexime (CEF). The results of X-ray photoelectron spectroscopy (XPS) and reflection-absorption infrared spectroscopy (RAIRS) confirmed the formation of the developed surfaces. CEF imprinted film was constructed by cyclic voltammetry (CV) for 9 cycles in the presence of 80mM pyrrole in phosphate buffer solution (pH 6.0) containing 20mM CEF. The developed electrochemical biosensor was validated according to the International Conference on Harmonisation (ICH) guideline and found to be linear, sensitive, selective, precise and accurate. The linearity range and the detection limit were obtained as 1.0×10-10-1.0×10-8M and 2.2×10-11M, respectively. The developed CEF imprinted sensor was successfully applied to real samples such as human plasma. In addition, the stability and reproducibility of the prepared molecular imprinted electrode were investigated. The excellent long-term stability and reproducibility of the prepared CEF imprinted electrodes make them attractive in electrochemical sensors. © 2014 Elsevier B.V.

CHAPS is a zwitterionic surfactant derivative of bile salts, widely used in membrane protein isolation. While some studies regarding CHAPS self-aggregation suggest continuous increase in micelle size at increasing CHAPS concentration, other works point to the existence of two definite micelle types. In this work, stearic acid spin labels (5, 12, or 16-SASL) were added to CHAPS solutions to obtain information about the micellar structure using electron paramagnetic resonance spectroscopy. The spectra of 12-SASL were processed using Principal Factor Analysis, and at all concentrations they could be reproduced as linear combinations of only three fundamental spectra, the first one corresponding to free 12-SASL in aqueous solution. This fact suggests only two hydrophobic environments that host 12-SASL, assigned to primary and secondary CHAPS micelles. The relative populations of the label in each environment were obtained as a function of CHAPS concentration. Our results suggest barrel-shaped primary micelles with a minimum mean radius of 1.46 nm, and a critical micelle concentration cmcI = 4 mM. Secondary micelles are formed by aggregation of primary ones, with cmcII = 10 mM. They have several elongated hydrophobic pockets, with similar dimensions for all aggregate sizes. Our results contribute to the understanding of the mechanism of interaction of chain amphiphiles with CHAPS micelles. Fil: Rodi, Pablo Marcelo. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas. Departamento de Física; Argentina Fil: Bocco Gianello, María D.. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas. Departamento de Física; Argentina Fil: Gennaro, Ana Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química (i); Argentina. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas. Departamento de Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Física del Litoral; Argentina

Self-assembly of four components has resulted into the formation of M 2L2 type dinuclear metallacyclophanes [Re(CO) 3Br(?-L)]2 (1-5), using flexible ester functionalised organic spacers and metal precursor containing fac-Re(CO)3 corners. The dinuclear metallacyclophanes were synthesized from ReBr(CO)5 and ditopic pyridyl ligands (L) (L = etdp, prdp, budp, pedp and hedp). The self-assembled compounds 1-5 were characterised by elemental analysis, IR, NMR, absorption and emission spectroscopic techniques. Molecular structure of 1 and 2 have been characterised by single crystal X-ray diffraction methods and the molecular masses of 3-5 were evaluated by ESI-MS. Cytotoxicity studies of metallacyclophanes 1, 3 and 5 on six different cancer and normal cells revealed that the metallacyclophanes selectively inhibit certain cancer cells. Especially, compound 5 showed broad-spectrum inhibitory activities in five cancer cells tested with low IC50 value comparable to a reference compound (cisplatin). The anticancer activity of compound 5 is attributed to the induction of early apoptosis. Hence, this class of compounds forms potential anticancer agents. � 2014 Elsevier B.V. All rights reserved.

We review recent developments in understanding the behaviour of equilibrium fluids with competing short-range attractions and long-range repulsions at low concentration. Typically, this SALR model system is used to represent solutions where at least one of the solute species interacts via a screened-coulomb potential, which includes many colloidal, nanoparticle and polyelectrolyte solutions among others. Provided neither the short-range or long-range interactions are too strong, and the concentration remains sufficiently low, then discrete spherical clusters of solute are expected, here called “Giant SALR clusters”. Because these clusters can themselves be disordered, as though fluid particles with a renormalised interaction, such cluster fluids cannot be treated using standard mean field methods. Our review therefore focuses on theoretical routes that aim to overcome this difficulty. We highlight the main outcomes of these theories and discuss how they relate to soft matter and especially biology, including complex coacervates, membraneless organelles and the origin of life.

Migration and chaining of noncolloidal spheres in a worm-like micellar, viscoelastic solution under shear flow have been studied both experimentally and by numerical simulations. The microstructure dynamics have been experimentally investigated in the flow-gradient and in the flow-vorticity planes. 20 simulations in the flow-gradient plane have been performed for the same geometry, and with a proper selection for the constitutive equation of the suspending liquid. Experimental results show the formation of particle chains in the bulk, along with migration of a considerable fraction of spheres to the walls. At long times, chains in the bulk are stable, and cross-flow migration of individual spheres is suppressed. Numerical simulations with a standard viscoelastic constitutive equation (Giesekus fluid) reproduce the same phenomena observed experimentally, both in terms of fast particle migration to the wall and bulk chain stability. No alignment is, instead, found in simulations with a constant-viscosity, elastic fluid (Oldroyd-B model), in agreement with previous experimental results with Boger fluids. (C) 2013 Elsevier B.V. All rights reserved.