Different Types Of Assemblies Research Articles

Reduced cytotoxicity of nanomaterials driven by nano-bio interactions: Case study of single protein coronas enveloping polymersomes

The protein adsorption onto poly(acrylic acid)-block-polystyrene (PAA22-b-PS144) polymersomes has been investigated with regard to structural features, thermodynamic aspects and biological consequences. The light scattering measurements revealed the formation of protein coronas enveloping the polymeric capsules regardless of the chemical nature of the biomacromolecules. The experiments were conducted by using lysozyme, immunoglobulin G - IgG and bovine serum albumin - BSA as model proteins due to their differences concerning size and residual surface charge at physiological pH. The protein adsorption was further confirmed by isothermal titration calorimetry, and the experimental data suggest that the phenomenon is mainly governed by hydrogen bonding and van der Waals interactions. The pre-existing protein layer via the pre-incubation in protein environments notably attenuates the cytotoxicity of the nanomaterial compared to the pristine counterparts. This approach can possibly be extended to different types of assemblies when intermolecular interactions are able to induce protein adsorption and the development of protein coronas around nanoparticles. Such fairly simple method may be convenient to engineer safer nanomaterials towards a variety of biomedical applications when the nanotoxicity is an issue. Additionally, the strategy can possibly be used to tailor the surface properties of nanoparticles by adsorbing specific proteins for targeting purposes.

Self-assembly of neutral platinum complexes controlled by thermal inputs.

In this report, we describe the self-assembly behavior of neutral platinum complexes in toluene. The platinum complexes were seen to form two different types of assemblies depending on the preparation temperature.

Langmuir and Langmuir–Blodgett films of aromatic amphiphiles

ABSTRACT Amphiphiles are molecules that contain two discrete segments – a water-soluble hydrophilic part (head-group) and a water-insoluble hydrophobic part (tail). The structural variations possible with the head-group part are enormous and numerous amphiphiles have been designed in this way. On the other hand, the structural variations feasible for the hydrophobic tail part are rather limited. Saturated aliphatic hydrocarbon chains are predominantly found in most of the amphiphiles. Unsaturated aliphatic hydrocarbon chains (n-alkenyl or n-alkynyl chains) also serve as the hydrophobic tail part in many of the amphiphiles. Amphiphiles, wherein the hydrophobic tail part is made up of aromatic moieties (alone or in combination with aliphatic chains) are less frequently encountered compared to the other two types. Many of these aromatic amphiphiles, the focus of this review article, are known to form different types of assemblies including Langmuir and Langmuir-Blodgett (LB) films. In this review, we will provide an account of the different types of aromatic amphiphiles that have been reported and highlight their properties and applications at the air–water and air–solid interfaces.

A reaction-diffusion model of spatial propagation of A[Formula: see text] oligomers in early stage Alzheimer's disease.

The misconformation and aggregation of the protein Amyloid-Beta (A[Formula: see text]) is a key event in the propagation of Alzheimer's Disease (AD). Different types of assemblies are identified, with long fibrils and plaques deposing during the late stages of AD. In the earlier stages, the disease spread is driven by the formation and the spatial propagation of small amorphous assemblies called oligomers. We propose a model dedicated to studying those early stages, in the vicinity of a few neurons and after a polymer seed has been formed. We build a reaction-diffusion model, with a Becker-Döring-like system that includes fragmentation and size-dependent diffusion. We hereby establish the theoretical framework necessary for the proper use of this model, by proving the existence of solutions using a fixed point method.

A General Fret-Based Method to Monitor Protein Oligomerization and Condensate Phase Transition in Cells

Proteins can self-assemble into a wide range of architectures, ranging from microscopically invisible small oligomers to condensates of varying structure and dynamics. These assemblies are essential for the functioning of the cell and are associated with many kinds of diseases. Because the intracellular environment influences assemblies concerning stoichiometry, structure, and dynamics, which is due to chaperone action or nonspecific interactions, it pertinent that these assemblies are monitored in a minimally invasive manner inside cells. Here we present a FRET-based method that allows detailed monitoring of protein self-assembly. The sensitive nature of this method allows monitoring the dynamic aggregation behavior and distinguishing different types of assemblies. We thus observe the dynamic structural transition between unstructured condensates and fibrils and confirm an array of previous observations on aggregations in yeast and HEK293. In addition, we find a distinct cell-to-cell variation in kinetics and structure of the respective condensates. This method is modular and easily implemented in other native or non-native proteins and will provide crucial insight into protein self-assembly.

From Prions to Stress Granules: Defining the Compositional Features of Prion-Like Domains That Promote Different Types of Assemblies.

Stress granules are ribonucleoprotein assemblies that form in response to cellular stress. Many of the RNA-binding proteins found in stress granule proteomes contain prion-like domains (PrLDs), which are low-complexity sequences that compositionally resemble yeast prion domains. Mutations in some of these PrLDs have been implicated in neurodegenerative diseases, including amyotrophic lateral sclerosis and frontotemporal dementia, and are associated with persistent stress granule accumulation. While both stress granules and prions are macromolecular assemblies, they differ in both their physical properties and complexity. Prion aggregates are highly stable homopolymeric solids, while stress granules are complex dynamic biomolecular condensates driven by multivalent homotypic and heterotypic interactions. Here, we use stress granules and yeast prions as a paradigm to examine how distinct sequence and compositional features of PrLDs contribute to different types of PrLD-containing assemblies.

On-demand tuning of charge accumulation and carrier mobility in quantum dot solids for electron transport and energy storage devices

Assemblies of colloidal quantum dots (CQDs) are attractive for a broad range of applications because of the ability to exploit the quantum confinement effect and the large surface-to-volume ratio due to their small dimensions. Each application requires different types of assemblies based on which properties are intended to be utilized. Greater control of assembly formation and optimization of the related carrier transport characteristics are vital to advance the utilization of these materials. Here, we demonstrate on-demand control of the assembly morphology and electrical properties of highly crosslinked CQD solids through the augmentation of various assembly methods. Employment of electric-double-layer (EDL) gating on these assembly structures (i.e., an amorphous assembly, a hierarchical porous assembly, and a compact superlattice assembly) reveals their intrinsic carrier transport and accumulation characteristics. Demonstrations of high electron mobility with a high current modulation ratio reaching 105 in compact QD films and of a record-high areal capacitance of 400 μF/cm2 in an electric-double-layer supercapacitor with very thin (<100 nm) QD hierarchical porous assemblies signify the versatility of CQDs as building blocks for various modern electronic devices.

Reorganization from Kinetically Stable Aggregation States to Thermodynamically Stable Nanotubes of BINOL-Derived Amphiphiles in Water.

The synthesis and self-assembly behavior of newly designed BINOL-based amphiphiles is presented. With minor structural modifications, the aggregation of these amphiphiles could be successfully tuned to form different types of assemblies in water, ranging from vesicles to cubic structures. Simple sonication induced the rearrangement of different kinetically stable aggregates into thermodynamically stable self-assembled nanotubes, as observed by cryo-TEM.

Physicochemistry of CTAB-SDS interacted catanionic micelle-vesicle forming system: An extended exploration

Interaction between cetyltrimethylammonium bromide (CTAB) and sodium dodecylsulfate (SDS) has been known to form different types of assemblies. The mixed surfactant solutions may form clear, translucent, turbid, and precipitate comprising mixed micelles, mixed mono- and multi-lamellar vesicles and their insoluble products. These properties have been herein explored under three different concentrations of the surfactants (CTAB and SDS) (1) below, (2) near, and (3) above their critical micelle concentration (CMC) up to their equi-molar proportions and above. Their phase forming behaviors, and critical vesicle concentrations were determined from turbidimetry, conductometry and calorimetry measurements. Fluorescence anisotropy measurements were taken to confirm vesicle formation. Vesicle dimension was assessed from dynamic light scattering measurements. ζ- potential of the studied assemblies were found to be both positive and negative depending on their composition ratios. The formed vesicles at 1:1 M composition were very stable; they were extracted by isooctane by partition method from the dispersion state. Polar nonaqueous solvents were found to make the turbid vesicular solutions clear. Increased temperature favored transition of vesicles to mixed micelles. Field Emission Scanning Electron Microscopy and Confocal Fluorescence Microscopy evidenced formation of ion-pair products as well as both uni-, and multi-layer vesicles of moderate and large prolate type sizes. Antibacterial properties of the vesicles were also tested against E. coli and B. subtilis showing fair inhibition activities. The present multifarious detailed study contributes new and global inputs in the field of a model self-aggregated microheterogeneous amphiphilic vesicular systems with possible extension to future investigations with newer amphiphiles viz. bolaforms, pluronics, ionic liquids, geminis, etc.

Amyloid-like aggregates formation by blood plasma fibronectin

Fibronectin (FN) is a multifunctional glycoprotein of the extracellular matrix (ECM) playing critical roles in physiological and pathological cell processes like adhesion, migration, growth, and differentiation. These various functions of FN are modulated by its supramolecular state. Indeed, FN can polymerize into different types of assemblies like fibrils and aggregates. However, the mechanism of polymerization and the effects of such assemblies on cell behaviors still remain to be elucidated. Here we show that upon irreversible thermal denaturation, human blood plasma fibronectin forms high molecular weight aggregates. These compact and globular aggregates show amyloid features: they are stabilized by intermolecular b-sheets, they bind Thioflavin T and they are resistant to reducing and denaturing agents. Their characterization by electrospray ionization charge detection mass spectrometry shows that two populations can be distinguished according to the mass and charge density. Despite their amyloid features and the presence of hydrophobic patches on their surface, these aggregates are not toxic for cells. However, their binding abilities to gelatin and RGD are drastically decreased compare to native FN, suggesting possible effects on ECM-cell interactions.

Controllable Two-Stage Droplet Evaporation Method and Its Nanoparticle Self-Assembly Mechanism

Bottom-up self-assembly is able to constitute a variety of structures and has been thought to be a promising way for advanced nanofabrication. Droplet evaporation, as the simplest method, has been used in various self-assemblies. However, the assembled area is not large enough and the order is still not well controlled. Here we show a facile and controllable two-stage droplet evaporation method by adjusting the humidity and temperature of the evaporating droplet. Taking the highly monodispersed gold nanorods (GNRs) as an example, large-area, self-assembly monolayer arrays are reproducibly achieved. To understand the self-assembly mechanism, we adopted simplified models to analyze the interactions between the nanorods. The results show that a metastable state of secondary-energy-minimum exists, especially in the latter stage of the assembly process, leading to the ordered arrays. A large electrostatic barrier between the assembled arrays prevents the formation of the multilayer structures and thereby leads to the preferential monolayers. Moreover, we predict possibilities of different types of assemblies of the nanorods, and a schematic phase diagram is finally given. The results here may offer a way toward high-quality self-assembled nanoparticles superlattices for use in enhanced spectroscopy, sensors, or nanodevices.

A note on application of superhomogénéisation factors to integro-differential neutron transport equations

The present article focuses on the application of the SPH factor method to the integro-differential neutron transport equation. While leakage-related parameters are arbitrarily corrected by the SPH factors, the correction procedure for these parameters affects the calculation accuracy. We treat two correction procedures named the simultaneous correction and the direct correction, and compare them with each other in one-dimensional colorset assembly problems. Through numerical testing, we find that the simultaneous SPH correction gives better accuracy than the direct SPH correction, and the higher-order SPH-corrected calculations show better accuracy than the low-order ones. Furthermore, to consider the flux discontinuity between different types of assemblies, the improved SPH method proposed by Yamamoto and the SPH method with the Selengut normalization condition are also tested. Numerical results reveal that the both methods significantly improve the calculation accuracy and that the latter method is more robust than the former method.

Evaluation of fluid flow in the lower core of a PWR with Code_ Saturne

In order to better understand the stresses to which fuel rods are subjected, we need to improve our knowledge of the fluid flow inside the core. The first spacer grid region is of particular interest, as fuel rod fretting has sometimes been observed at that level. Entry conditions depend on the geometry of the lower core plate and of the assembly nozzles. Distribution of flow in the downcomer and lower plenum is also a factor. A series of calculations are thus run with the incompressible Navier–Stokes solver, Code_ Saturne, using a classical RANS turbulence model. The first calculations involve a global geometry, including part of the cold legs, downcomer, lower plenum, and lower core of a pressurized water reactor. The level of detail includes most obstacles below the core. The lower core plate and the fuel rod assemblies above it cannot be well represented within a practical mesh size, so that a head loss model is used. Different types of assemblies can be represented through different head loss coefficients. We make full use of Code_ Saturne’s non-conforming mesh possibilities to represent a complex geometry, being careful to retain a good mesh quality. Steady-state or near steady-state results are obtained, which may be used as realistic entry conditions for full core calculations at assembly width resolution, and beyond those, mechanical strain calculations. We are especially interested in more detailed flow conditions and in the lower core area, so as in the future to quantify vibrational input. This requires a much higher resolution, which is limited to a scale of a few assemblies for practical reasons. At this scale, most of the features of the fuel rods, nozzles, and guide tubes are represented, though the geometry of the spacer grids is still much simplified, and details such as debris-trapping grids are ignored. Different meshes are used for different fuel types. For the moment, a constant velocity upstream of the lower core plate is used as an inlet condition. We have also built a small lower fuel rod assembly mock-up (1/5 scale 7 × 7 tube, 3 × 3 assemblies) with which we plan to obtain detailed flow information, and better qualify the use of our CFD codes with regards to this type of application.

Distinct cohesin complexes organize meiotic chromosome domains.

Meiotic cohesin complexes at centromeres behave differently from those along chromosome arms, but the basis for these differences has remained elusive. The fission yeast cohesin molecule Rec8 largely replaces its mitotic counterpart, Rad21/Scc1, along the entire chromosome during meiosis. Here we show that Rec8 complexes along chromosome arms contain Rec11, whereas those in the vicinity of centromeres have a different partner subunit, Psc3. The arm associated Rec8-Rec11 complexes are critical for meiotic recombination. The Rec8-Psc3 complexes comprise two different types of assemblies. First, pericentromeric Rec8-Psc3 complexes depend on histone methylation-directed heterochromatin for their localization and are required for cohesion during meiosis II. Second, central core Rec8-Psc3 complexes form independently of heterochromatin and are presumably required for establishing monopolar attachment at meiosis I. These findings define distinct modes of assembly and functions for cohesin complexes at different regions along chromosomes.

Effect of the Magnetostrictive Layer on Magnetoelectric Properties in Lead Zirconate Titanate/Terfenol‐D Laminate Composites

Magnetoelectric laminate composites of piezoelectric/magnetostrictive materials were prepared by stacking and bonding together a PZT disk and two layers of Terfenol‐D disks with different directions of magnetostriction. These composites were studied to investigate (i) dependence on the magnetostriction direction of the Terfenol‐D disk and (ii) dependence on the direction of the applied ac magnetic field. Three different types of assemblies were prepared by using two types of disks: one with magnetostriction along the radial direction, the other with magnetostriction along the thickness direction. The maximum magnetoelectric voltage coefficient (dE/dH) of 5.90 V/cm·Oe was obtained for a design where the composite was made by two Terfenol‐D layers with a radial magnetostriction direction.

Ten rules of fire endurance rating

Fire endurance tests alone cannot supply all the data needed for intelligent appraisal of fire resistant ratings of building elements. There are simply too many different types of assemblies and combinations of materials to classify them all through actual tests. Fortunately, the theory of fire endurance rating is sufficiently advanced to offer guidance in estimating fire endurance ratings. The author sets forth ten rules that may prove useful for quick assessment of the fire endurance of building elements when fire test data on the elements are not available.