Asymmetric Interface Research Articles

Surfactant protein D inhibits activation of non-small cell lung cancer-associated mutant EGFR and affects clinical outcomes of patients.

Tyrosine kinase inhibitor (TKI)-sensitive and TKI-resistant mutations of epidermal growth factor receptor (EGFR) are associated with lung adenocarcinoma. EGFR mutants were previously shown to exhibit ligand-independent activation. We have previously demonstrated that pulmonary surfactant protein D (SP-D, SFTPD) suppressed wild-type EGFR signaling by blocking ligand binding to EGFR. We herein demonstrate that SFTPD downregulates ligand-independent signaling in cells harboring EGFR mutations such as TKI-sensitive exon 19 deletion (Ex19del) and L858R mutation as well as TKI-resistant T790M mutation, subsequently suppressing cellular growth and motility. Lectin blotting and ligand blotting in lung cancer cell lines suggested that EGFR mutants express oligomannose-type N-glycans and interact with SFTPD directly. Cross-linking assay indicated that SFTPD inhibits ligand-independent dimerization of EGFR mutants. We also demonstrated that SFTPD reduced dimerization-independent phosphorylation of Ex19del and T790M EGFR mutants using point mutations that disrupted the asymmetric dimer interface. It was confirmed that SFTPD augmented the viability-suppressing effects of EGFR-TKIs. Furthermore, retrospective analysis of 121 patients with lung adenocarcinoma to examine associations between serum SFTPD levels and clinical outcome indicated that in TKI-treated patients with lung cancer harboring EGFR mutations, including Ex19del or L858R, high serum SFTPD levels correlated with a lower number of distant metastases and prolonged overall survival and progression-free survival. These findings suggest that SFTPD downregulates both TKI-sensitive and -resistant EGFR mutant signaling, and SFTPD level is correlated with clinical outcome. These findings illustrate the use of serum SFTPD level as a potential marker to estimate the efficacy of EGFR-TKIs.

Improved Interfacial Floatability of Superhydrophobic/Superhydrophilic Janus Sheet Inspired by Lotus Leaf

Interfacial materials exhibiting superwettability have emerged as important tools for solving the real‐world issues, such as oil‐spill cleanup, fog harvesting, etc. The Janus superwettability of lotus leaf inspires the design of asymmetric interface materials using the superhydrophobic/superhydrophilic binary cooperative strategy. Here, the presented Janus copper sheet, composed of a superhydrophobic upper surface and a superhydrophilic lower surface, is able to be steadily fixed at the air/water interfaces, showing improved interfacial floatability. Compared with the floatable superhydrophobic substrate, the Janus sheet not only floats on but also attaches to the air–water interface. Similar results on Janus sheet are discovered at other multiphase interfaces such as hexane/water and water/CCl4 interfaces. In accordance with the improved stability and antirotation property, the microboat constructed by a Janus sheet shows the reliable navigating ability even under turbulent water flow. This contribution should unlock more functions of Janus interface materials, and extend the application scope of the binary cooperative materials system with superwettability.

Thermal transport across symmetric and asymmetric solid–solid interfaces

Thermal transport across symmetric and asymmetric solid–solid interfaces is investigated by non-equilibrium molecular dynamics simulations. For symmetric interfaces, simulation results demonstrate that the thermal interface resistance is reduced greatly with the temperature increasing from 20 to 70 K. Besides, the introduction of an interlayer in the region of a highly mismatched interface is predicted to effectively decrease the thermal interface resistance due to the vibrational bridge role of the interlayer in connecting two vibrationally mismatched materials. As for the case of asymmetric interfaces, it is found that the capacity of thermal transport across an asymmetric interface is related to the effective interfacial area, namely the smaller cross-section area of component materials. In addition, effects of the transition angle at asymmetric interfaces on the thermal interface resistance are further studied when heat flows through interfaces from the side with larger cross-section area to the other. It is shown that a smoother transition is preferred for thermal transport through an asymmetric interface.

Ultrastructural Analysis of Self-Associated RyR2s

In heart, type-2 ryanodine receptor (RyR2) forms discrete supramolecular clusters in the sarcoplasmic reticulum known as calcium release units (CRUs), which are responsible for most of the Ca2+ released for muscle contraction. To learn about the substructure of the CRU, we sought to determine whether RyR2s have the ability to self-associate in the absence of other factors and if so, whether they do it in a specific manner. Purified RyR2 was negatively stained and imaged on the transmission electron microscope, and RyR2 particles closely associated were further analyzed using bias-free multivariate statistical analysis and classification. The resulting two-dimensional averages show that RyR2s can interact in two rigid, reproducible configurations: “adjoining”, with two RyR2s alongside each other, and “oblique”, with two partially overlapped RyR2s forming an angle of 12°. The two configurations are nearly identical under two extreme physiological Ca2+ concentrations. Pseudo-atomic models for these two interactions indicate that the adjoining interaction involves contacts between the P1, SPRY1 and the helical domains. The oblique interaction is mediated by extensive contacts between the SPRY1 domains (domains 9) and P1 domains (domains 10) of both RyR2s and not through domain 6 as previously thought; in addition its asymmetric interface imposes steric constrains that inhibit the growth of RyR2 as a checkerboard, which is the configuration usually assumed, and generates new configurations, i.e., “branched” and “interlocked”. This first, to our knowledge, structural detailed analysis of the inter-RyR2 interactions helps to understand important morphological and functional aspects of the CRU in the context of cardiac EC coupling.

Neutron reflectometry study of CrAlN/TiAlN nanostructured multilayers

Alternate CrAlN/TiAlN multilayers with different repeated bilayer thickness ranging from 10 to 20 nm were prepared by sputtering Ti, Al and Cr targets with N2 and Ar gases. The interface structures of multilayers such as the average individual thicknesses, the scattering length densities and interface roughness were characterized using nonpolarized specular neutron reflectometry. The experimental reflectivity can be well described by a multilayer model for all samples. The individual thickness in the repeated bilayers is close to the nominal thickness. The interface roughness diminishes as the thickness of the bilayer in mutilayers decreases. The asymmetric interface roughness on CrAlN‐TiAlN‐Si interfaces causes the larger interface roughness of CrAlN on TiAlN interface. The scattering length density profiles of multilayers suggest that the chemical composition is approximate to Cr0.86Al0.14N/Ti0.5Al0.5N and which is more accurate for thinner films. Copyright © 2016 John Wiley & Sons, Ltd.

The effect of amidation on the behaviour of antimicrobial peptides.

Aurein 2.6-COOH and aurein 3.1-COOH were studied along with their naturally occurring C-terminally amidated analogues. Circular dichroism (CD) and molecular dynamic (MD) simulations were used to study the effects of amidation on the interaction of antimicrobial peptides (AMPs) with lipid bilayers. CD measurements and MD analysis suggested that both peptide analogues were predominantly random coil and adopted low levels of alpha-helical structure in solution (<30 %) and in the presence of a lipid bilayer the peptides formed a stable alpha-helical structure. In general, amidated analogues have a greater propensity than the non-amidated peptides to form a alpha-helical structure. MD simulations predicted that aurein 2.6-COOH and aurein 3.1-CHOOH destabilised lipid bilayers from 1,2-dimyristoyl-sn-glycero-3-phosphocholine and 1,2-dimyristoyl-sn-glycero-3-phosphoserine via angled bilayer penetration. They also showed that aurein 2.6-CONH_2 and aurein 3.1-CONH_2 formed a helix horizontal to the plane of an asymmetric interface.Electronic supplementary materialThe online version of this article (doi:10.1007/s00249-015-1094-x) contains supplementary material, which is available to authorized users.

Inhibition of minority transport for elevating the thermoelectric figure of merit of CuO/BiSbTe nanocomposites at high temperatures

In BiSbTe based composite with 0.2 vol% of CuO nanoinclusions, thermoelectric figure of merit increases monotonically and largest ZT = 1.37 was obtained at 496 K by inhibiting the transport of minorities at introduced asymmetric interface potentials.

Understanding the Electrochemical Properties of Li-Rich Cathode Materials from First-Principles Calculations

The lithium-rich layered oxide materials (LLOs) have attracted much attention as candidates for the next generation of LIBs because of their high voltage and high capacity, which are still poorly understood. In this study, the origin of high voltage and high capacity of LLOs has been comprehensively investigated through first-principles calculations. It is revealed that due to the asymmetric oxidation behavior of Li2MnO3/LiMO2 interface, the transition-metal–oxygen (TMO) layer of Li2MnO3 phase in Li-rich materials gains more electrons from Li layer than that in pure Li2MnO3, which results in the stronger hybrid between Mn-3d and O-2p states enhancing the activity of Mn in Li2MnO3. Moreover, the deintercalated Li-rich models possess smaller spacing than pure LiMO2, which reflects stronger electrostatic interaction between TMO and Li layers. The two factors are both beneficial to the high voltage of the Li-rich materials. However, the asymmetric interface also results in the increase of electronic states of...

Complex Nanotwin Substructure of an Asymmetric Σ9 Tilt Grain Boundary in a Silicon Polycrystal.

Grain boundaries in materials have substantial influences on device properties, for instance on mechanical stability or electronic minority carrier lifetime in multicrystalline silicon solar cells. This applies especially to asymmetric, less ordered or faceted interface portions. Here, we present the complex atomic interface structure of an asymmetric Σ9 tilt grain boundary in silicon, observed by high resolution scanning transmission electron microscopy (HR-STEM) and explained by atomistic modeling and computer simulation. Structural optimization of interface models for the asymmetric Σ9 and related symmetrical Σ9 and Σ3 tilt grain boundaries, by means of molecular-statics simulations with empirical silicon potentials in combination with first-principles calculations, results in a faceted asymmetric interface structure, whose grain-boundary energy is so low that it is likely to exist. The simulated local atomic structures match the observed HR-STEM images very well.

Orchestration of ErbB3 signaling through heterointeractions and homointeractions.

Members of the ErbB family of receptor tyrosine kinases are capable of both homointeractions and heterointeractions. Because each receptor has a unique set of binding sites for downstream signaling partners and differential catalytic activity, subtle shifts in their combinatorial interplay may have a large effect on signaling outcomes. The overexpression and mutation of ErbB family members are common in numerous human cancers and shift the balance of activation within the signaling network. Here we report the development of a spatial stochastic model that addresses the dynamics of ErbB3 homodimerization and heterodimerization with ErbB2. The model is based on experimental measures for diffusion, dimer off-rates, kinase activity, and dephosphorylation. We also report computational analysis of ErbB3 mutations, generating the prediction that activating mutations in the intracellular and extracellular domains may be subdivided into classes with distinct underlying mechanisms. We show experimental evidence for an ErbB3 gain-of-function point mutation located in the C-lobe asymmetric dimerization interface, which shows enhanced phosphorylation at low ligand dose associated with increased kinase activity.

Contrasting interedge superexchange interactions of graphene nanoribbons embedded inh-BN and graphane

Based on first-principles density-functional theory calculations, we present a comparative study of the elec- tronic structures of ultranarrow zigzag graphene nanoribbons (ZGNRs) embedded in hexagonal boron nitride (BN) sheet and fully hydrogenated graphene (graphane) as a function of their width N (the number of zigzag C chains composing the ZGNRs). We find that ZGNRs/BN have the nonmagnetic ground state except at N = 5 and 6 with a weakly stabilized half-semimetallic state, whereas ZGNRs/graphane with N >= 2 exhibit a strong antiferromagnetic coupling between ferromagnetically ordered edge states on each edge. It is revealed that the disparate magnetic properties of the two classes of ZGNRs are attributed to the contrasting interedge superexchange interactions arising from different interface structures: i.e., the asymmetric interface structure of ZGNRs/BN gives a relatively short-range and weak superexchange interaction between the two inequivalent edge states, while the symmetric interface structure of ZGNRs/graphane gives a long-range, strong interedge superexchange interaction.

Observation of interface dependent spin polarized photocurrents in InAs/GaSb superlattice

In this letter, we investigated the spin polarized photocurrents excited by mid-infrared radiation and near-infrared radiation, respectively, in InAs/GaSb type II superlattices with different kinds of interfaces. By periodically varying the polarization state of the radiation, we analyzed Rashba-type and Dresselhaus-type spin polarized photocurrents, which present different features depending on the interface types and excitation conditions. Under mid-infrared excitation, the ratio of Rashba-type and Dresselhaus-type spin polarized photocurrents of the superlattice with InSb-like interface is obviously larger than that of the superlattice with GaAs-like interface, the ratio of the superlattice with alternate interface is in the middle. Whereas under near-infrared excitation, the ratios of the three superlattices are nearly the same. Further researches reveal the synactic effects of interface dependent strain and asymmetric interface potential on the spin splitting. Besides, the polarized Raman spectroscopies of these structures were also analyzed.

Design and construction of the lawnmower, an artificial burnt-bridges motor.

Molecular motors of the cell are protein-based, nanoscale machines, which use a variety of strategies to transduce chemical energy into mechanical work in the presence of a large thermal background. The design and construction of artificial molecular motors is one approach to better understand their basic physical principles. Here, we propose the concept of a protein-based, burnt-bridges ratchet, inspired by biological examples. Our concept, the lawnmower, utilizes protease blades to cleave peptide substrates, and uses the asymmetric substrate-product interface arising from productive cleavage to bias subsequent diffusion on the track (lawn). Following experimental screening to select a protease to act as the motor's blades, we chemically couple trypsin to quantum dots and demonstrate activity of the resulting lawnmower construct in solution. Accompanying Brownian dynamics simulations illustrate the importance for processivity of correct protease density on the quantum dot and spacing of substrates on the track. These results lay the groundwork for future tests of the protein-based lawnmower's motor performance characteristics.

Coded Schemes for Asymmetric Wireless Interfaces: Theory and Practice

A fundamental understanding of the delay and throughput benefits of network coding over multiple heterogeneous half-duplex communication interfaces is critical to fully exploit current and future devices that incorporate multiple communication technologies. The goal of this paper is twofold. First, to present fundamental limits and several strategies to tradeoff data and feedback when using multiple interfaces. Our work sets forth a systematic approach to i) analyze a variety of schemes in the presence of channels with heterogeneous round-trip delays, packet transmission rates, and packet loss probability, and to ii) determine the optimal number of transmissions to be allocated to each channel based on these characteristics. Our analytical results show that the gains over a variety of uncoded approaches can be several fold and that our proposed strategies are within 1 dB to an optimal system with full duplex interfaces over a wide range of operating conditions. Our second goal is to understand the practical implications of these results by designing a protocol for file transmissions, implement it in Android smart phones, and measure its performance when combining various interfaces, including, Bluetooth, WiFi, and 3G cellular networks. Our measurements show that throughput is increased not only by the aggregation of multiple interfaces but also by providing a much more robust erasure correction mechanism.

Numerical modeling of flow evolution for an internal solitary wave propagating over a submerged ridge

Numerical simulations are performed to investigate the flow evolution of a depression ISW propagating over a submerged ridge. A finite volume based Cartesian grid method is adopted to solve the Reynolds averaged Navier–Stokes equations using a k−ε model for the turbulent closure. Results reveal a significant transient clockwise vortex and an internal hydraulic jump emerging on the front slope of the obstacle, during the wave–obstacle interaction. This interaction generates an asymmetrical interface and pycnocline thickness on both sides of the obstacle. During this process, the amplitude and velocity of the leading waveform increase transiently, but both quickly decrease once the wave passes the obstacle. As the ridge slope decreases, the wave–ridge interaction weakens, as well as the strength of vorticity and turbulent kinetic energy. In addition, the wave may affect the nutrient transport on the front slope to a maximum depth about 50% height of the obstacle or about 1.78 times of the incident wave amplitude when a large ISW breaks on the slope.

Numerical investigation on the melting of nanoparticle-enhanced phase change materials (NEPCM) in a bottom-heated rectangular cavity using lattice Boltzmann method

Convection melting of water (ice)–copper nanoparticles as a nanoparticle-enhanced phase change material (NEPCM) in a bottom-heated rectangular cavity is investigated numerically in this paper. A novel lattice Boltzmann (LB) method is developed to solve the solid–liquid phase change coupled with natural convection, in which two sets of evolution functions (density evolution function and temperature evolution function) are constructed to simulate fluid flow and heat transfer. The latent heat source term in temperature evolution function is treated with an implicit scheme, avoiding iteration steps as compared with previous methodologies. The moving melting interface is treated with an immersed moving boundary scheme, which makes it simple for the implementation of non-slip velocity condition on the solid–liquid interface. The predictions of the current model are compared with previous numerical and experimental results, and a reasonable agreement is obtained. And then the developed model is employed to study the impacts of the volume fraction of nanoparticles and the Grashof number on the flow structure and heat transfer characteristics. The computed results show that the NEPCM exhibits high heat transfer efficiency in comparison to the pure phase change material (PCM). As the volume fraction of nanoparticles increases, the temperature field and melting interface evolves faster, and the melt fraction and energy stored increases. In addition, for high volume fraction of nanoparticles at a Grashof number Gr = 2.5 × 10 5 , an asymmetric melting interface forms due to the asymmetric distribution of the convection cells.

Field- and Current-Induced Domain Wall Motion in Tb/Co Multilayers in the Presence of Spin-Orbit Coupling-Induced Torques

We have studied the field- and current-induced domain wall (DW) motion in perpendicularly magnetized Tb/Co multilayer wires with asymmetric interface structures. We found that both up/down and down/up walls of a domain move at the same velocity. In the current-induced case, the DWs were moved along the current flow, not electron flow. This can be attributed to spin-orbit torques induced by structural inversion asymmetry (SIA). In addition, the DW velocity was changed by inserting ultrathin Pt interlayers into the wire stack. These results suggest that the SIA of the wire is tunable by changing layered structures.

SPH Analysis on Formation Manner of Wavy Joint Interface in Impact Welded Al/Cu Dissimilar Metal Plates

The impact welding was performed for several kinds of metal plate couples. The joint interface exhibited a sinusoidal wave form when two metal plates with the same or similar density (e.g. Al/Al, Cu/Cu and Cu/Ni) were impact-welded by high-speed oblique collision. In contrast, as for dissimilar metal plate couples with large density difference such as Al/Cu, an asymmetric wavy interface was obtained. In order to make clear the reason for morphological difference, a computer simulation of the collision behavior was performed using SPH (Smooth Particle Hydrostatic) method. The simulation results revealed that the wave form was controlled by the interaction between the emitted metal jet and metal plate surfaces ahead of the collision point. For Al/Al and Cu/Ni, the emitted metal jet hit each surface alternatively and this resulted in symmetrical wavy interface formation. While, for Al/Cu, the metal jet was emitted to the direction parallel to the Cu plate, and the interaction took place between the metal jet and the Cu plate surface. The metal jet emission and wavy interface formation mechanism were also investigated.

Effect of interface configurations on the dynamic scaling behavior of Pb(Zr0.53Ti0.47)O3 thin films

The ferroelectric hysteresis and the scaling relations of hysteresis area ⟨A⟩ against field amplitude E and frequency f in Pb(Zr0.53Ti0.47)O3 thin films using platinum and LaNiO3 (LNO) as both bottom and top electrodes were systematically investigated. Interestingly, it was found that the influence of top electrodes is dominant in affecting the scaling behavior of the dynamic hysteresis, which may be the result of the asymmetric interface structure deriving from the differences in conductivity and crystallization of the top and bottom LNO electrodes. The bottom electrodes affect the scaling behavior slightly via influencing the micro-structural and level of space charge.

An asymmetric heterodomain interface stabilizes a response regulator-DNA complex.

Two-component signal transduction systems consist of pairs of histidine kinases and response regulators, which mediate adaptive responses to environmental cues. Most activated response regulators regulate transcription by binding tightly to promoter DNA via a phosphorylation-triggered inactive-to-active transition. The molecular basis for formation of stable response regulator-DNA complexes that precede the assembly of RNA polymerases is unclear. Here, we present structures of DNA complexed with the response regulator KdpE, a member of the OmpR/PhoB family. The distinctively asymmetric complex in an active-like conformation reveals a unique intramolecular interface between the receiver domain (RD) and the DNA-binding domain (DBD) of only one of the two response regulators in the complex. Structure-function studies show that this RD-DBD interface is necessary to form stable complexes that support gene expression. The conservation of sequence and structure suggests that these findings extend to a large group of response regulators that act as transcription factors.