Cation–π Interaction Trigger Supramolecular Hydrogelation of Peptide Amphiphiles

As an important noncovalent interaction, cation–π interaction plays an essential role in a broad area of biology and chemistry. Despite extensive studies in protein stability and molecular recognition, the utilization of cation–π interaction as a major driving force to construct supramolecular hydrogel remains uncharted. Here, a series of peptide amphiphiles are designed with cation–π interaction pairs that can self-assemble into supramolecular hydrogel under physiological condition. The influence of cation–π interaction is thoroughly investigated on peptide folding propensity, morphology, and rigidity of the resultant hydrogel. Computational and experimental results confirm that cation–π interaction could serve as a major driving force to trigger peptide folding, resultant β-hairpin peptide self-assembled into fibril-rich hydrogel. Furthermore, the designed peptides exhibit high efficacy on cytosolic protein delivery. As the first case of using cation–π interactions to trigger peptide self-assembly and hydrogelation, this work provides a novel strategy to generate supramolecular biomaterials.     

Ion‐Migration Inhibition by the Cation–π Interaction in Perovskite Materials for Efficient and Stable Perovskite Solar Cells

Migration of ions can lead to photoinduced phase separation, degradation, and current–voltage hysteresis in perovskite solar cells (PSCs), and has become a serious drawback for the organic–inorganic hybrid perovskite materials (OIPs). Here, the inhibition of ion migration is realized by the supramolecular cation–π interaction between aromatic rubrene and organic cations in OIPs. The energy of the cation–π interaction between rubrene and perovskite is found to be as strong as 1.5 eV, which is enough to immobilize the organic cations in OIPs; this will thus will lead to the obvious reduction of defects in perovskite films and outstanding stability in devices. By employing the cation‐immobilized OIPs to fabricate perovskite solar cells (PSCs), a champion efficiency of 20.86% and certified efficiency of 20.80% with negligible hysteresis are acquired. In addition, the long‐term stability of cation‐immobilized PSCs is improved definitely (98% of the initial efficiency after 720 h operation), which is assigned to the inhibition of ionic diffusions in cation‐immobilized OIPs. This cation–π interaction between cations and the supramolecular π system enhances the stability and the performance of PSCs efficiently and would be a potential universal approach to get the more stable perovskite devices.     

Performance of combinatorial peptide libraries in capturing the low-abundance proteome of red blood cells. 2. Behavior of resins containing individual amino acids

Sixteen different amino acids (Arg, Asn, Asp, Gln, Glu, Gly, His, Ile, Lys, Phe, Pro, Ser, Thr, Trp, Tyr, Val) have been separately linked to chromatographic beads and used for studying the mechanism of binding of such baits to proteins, as represented by the cytoplasmic proteome of the human red blood cell (RBC). The 16 different amino acid columns were confronted with equal amounts of RBC lysate, washed to remove unbound material, and eluted with denaturing agents. All eluates were analyzed by nanoLC-MS/MS. The results: there appears to be a dichotomy between a class of "Grand Catchers" (Arg, His, Ile, Lys, Phe, Trp, Tyr, Val), all able to bind from 330 up to 441 unique gene products, and the "Petite Catchers" (Asn, Asp, Gln, Glu, Gly, Pro, Ser, Thr), that bind in general half as much, with the notable exception of Glu that under the described conditions seems to bind only traces of proteins. By comparing homogeneous classes of amino acids (e.g., the basic, the hydrophobic aromatic, the neutral hydrophilic, etc.), it is found that, in general, more than half as many proteins are held in common among the members of each family. In a 16-way comparison, 72 proteins (less than 10% of the total amount, which amounts to 800 unique, nonredundant, identified proteins) appear to be the common catch of all 16 amino acids, suggesting that such proteins might have either multiple binding sites or general motifs recognized by any generic bait. By far, it would appear that the strongest interactions and thus the strongest catches occur with the three aromatic moieties of Phe, Trp, and Tyr, all able to capture a practically identical number of proteins. Ionic interactions, which in principle should be the strongest ones, appear to behave in a peculiar way: they are quite strong with the three basic amino acids (Arg, His, Lys) but almost inexistent with their acidic counterparts. This suggests a peculiar mechanism of interaction: upon formation of the ion pair, the linkage between the protein and the bait is stabilized by the hydrophobicity of the underlying chain (e.g., a butyl in the case of Lys).     

Cation–π Interactions in Graphene-Containing Systems for Water Treatment and Beyond

Cation–π interactions are common in nature, especially in organisms. Their profound influences in chemistry, physics, and biology have been continuously investigated since they were discovered in 1981. However, the importance of cation–π interactions in materials science, regarding carbonaceous nanomaterials, has just been realized. The interplay between cations and delocalized polarizable π electrons of graphene would bring about significant changes to the intrinsic characteristics of graphene and greatly affect the device performance based on graphene and its derivatives. Here, the cation–π interactions in graphene containing systems for water treatment applications (e.g., separation membranes, adsorbents) are highlighted. The cross-linking effects caused by cation–π interactions contribute to membrane stability and selectivity and enhanced adsorption. Their roles in dominating the performance of graphene-based structures for other specific applications are also discussed. Relevant theoretical modeling and calculations are summarized to offer an in-depth understanding of the underlying mechanisms which can help in designing more functional materials and structures. Perspectives on the potential directions that deserve effort are also presented.     

Effects of bioactive ceramics on the pathogenesis of rat vascular smooth muscle cells treated with phorbol 12-myristate 13-acetate

Vascular smooth muscle cells (VSMCs) play a pivotal role in vascular injury through proliferation and migration. Pro-inflammatory cytokines and cyclooxygenase (COX)-2 and nitric oxide synthase (NOS) are highly associated with the pathogenesis of VSMCs. We investigated the effect of bioactive ceramics on the expression of inflammatory cytokines, COX-2, and inducible NOS (iNOS) induced by phorbol 12-myristate 13-acetate (PMA) in rat VSMCs. The ceramics inhibited mRNA expression of IL-1β, TNF-α, IL-6, COX-2, and iNOS. Prostaglandin release was also diminished by the ceramics. The bioactive ceramics effect on cytokines, COX-2, and iNOS expression was achieved by inhibition of NF-κB activity. Interestingly, the ceramics-induced up-regulation of expression of endothelial NOS resulted in an increase of nitric oxide production. Thus, bioactive ceramics may have dual effects on the pathogenesis of VSMCs by regulation of NF-κB activity and NO production.     

Nanoparticle-induced unfolding of fibrinogen promotes Mac-1 receptor activation and inflammation

The chemical composition, size, shape and surface characteristics of nanoparticles affect the way proteins bind to these particles, and this in turn influences the way in which nanoparticles interact with cells and tissues. Nanomaterials bound with proteins can result in physiological and pathological changes, including macrophage uptake, blood coagulation, protein aggregation and complement activation, but the mechanisms that lead to these changes remain poorly understood. Here, we show that negatively charged poly(acrylic acid)-conjugated gold nanoparticles bind to and induce unfolding of fibrinogen, which promotes interaction with the integrin receptor, Mac-1. Activation of this receptor increases the NF-κB signalling pathway, resulting in the release of inflammatory cytokines. However, not all nanoparticles that bind to fibrinogen demonstrated this effect. Our results show that the binding of certain nanoparticles to fibrinogen in plasma offers an alternative mechanism to the more commonly described role of oxidative stress in the inflammatory response to nanomaterials.     

AFM观察小鼠心肌核DNA转录调控和蛋白质相互作用

用原子力显微镜(AFM)直接观察、体外转录、PAGE冠电泳等多种实验技术组合，发现小白民(Balb/c)心肌核DNA片段中非转录状态的活性基因仅两端的调控序列结合支架蛋白(不可解离蛋白)，同时非共价键特异结合自己编码的蛋白质与特定辅助信息小分子所形成的复合体(可解离蛋白)等多种转录调控蛋白质，中间的编码序列无结合蛋白质。转录状态的基因除两端的调控序列特异结合上述两类蛋白质外，中间的编码序列还以非共价键特异结合可完全解离的转录活性因子等多种蛋白质。本工作展示了未来运用AFM观察和体外转录等技术组合研究基因表达与调控机制约前景，并为阅读人类基因组图谱中确定某一特定基因的位置奠定了理论基础。     

Mechanical properties of graphene films enhanced by homo-telechelic functionalized polymer fillers via π–π stacking interactions

Most researches on graphene/polymer composites are focusing on improving the mechanical and electrical properties of polymers at low graphene content instead of paying attention to constructing graphene’s macroscopic structures. In current study the homo-telechelic functionalized polyethylene glycols (FPEGs) were tailored with π-orbital-rich groups (namely phenyl, pyrene and di-pyrene) via esterification reactions, which enhanced the interaction between polyethylene glycol (PEG) molecules and chemical reduced graphene oxide (RGO) sheets. The π–π stacking interactions between graphene sheets and π-orbital-rich groups endowed the composite films with enhanced tensile strength and tunable electrical conductivity. The formation of graphene network structure mediated by the FPEGs fillers via π–π stacking non-covalent interactions should account for the experimental results. The experimental investigations were also complemented with theoretical calculation using a density functional theory. Atomic force microscope (AFM), scanning electron microscope (SEM), X-ray diffraction (XRD), nuclear magnetic resonance (NMR), thermal gravimetric analysis (TGA), UV–vis and fluorescence spectroscopy were used to monitor the step-wise preparation of graphene composite films.     

In Situ Investigation on the Protein Corona Formation of Quantum Dots by Using Fluorescence Resonance Energy Transfer

A fundamental understanding of nanoparticle–protein corona and its interactions with biological systems is essential for future application of engineered nanomaterials. In this work, fluorescence resonance energy transfer (FRET) is employed for studying the protein adsorption behavior of nanoparticles. The adsorption of human serum albumin (HSA) onto the surface of InP@ZnS quantum dots (QDs) with different chirality (d ‐ and l ‐penicillamine) shows strong discernible differences in the binding behaviors including affinity and adsorption orientation that are obtained upon quantitative analysis of FRET data. Circular dichroism spectroscopy further confirms the differences in the conformational changes of HSA upon interaction with d ‐ and l ‐chiral QD surfaces. Consequently, the formed protein corona on chiral surfaces may affect their following biological interactions, such as possible protein exchange with serum proteins plasma as well as cellular interactions. These results vividly illustrate the potential of the FRET method as a simple yet versatile platform for quantitatively investigating biological interactions of nanoparticles.     

Study of the non-covalent interactions in Langmuir-Blodgett films: An interplay between π−π and dipole-dipole interactions

This work describes Langmuir-Blodgett (L-B) monolayer and multilayer assemblies constructed from a series of NLO-active azo-benzene derivatives possessing terminal moieties of variable dipole moment. The terminal groups are electron acceptors (acetyl, nitro, and cyano) and are connected to a common amphiphilic azo-benzene segment. Our experimental and theoretical results show that the interplay between two dominant non-covalent interactions within the assemblies, namely dipolar and π−π stacking interactions, dictate the packing density, structural order, as well as the electronic properties of the final films. L-B films of the acetyl derivative, which has the weakest total dipole across the azo-benzene chromophore, exhibits the highest packing density and the largest blue shift in the UV-visible absorption spectrum. This is rationalized by relatively strong π−π interactions between the azo-benzene chromophores overwhelming weak intermolecular dipole-dipole interactions. More importantly, the small internal dipole in the acetyl functional groups encourages packing in a configuration that lowers the overall energy and increases the packing density. In the case of the cyano and nitro derivatives, both L-B films show decrease in packing density and a weaker electronic coupling due to unfavorable overall dipole interaction that offsets the π−π interaction. We show that such unfavorable interactions lead to the formation of a staggered and loosely packed configuration. Our work demonstrates that a subtle difference in molecular structure can have a dramatic impact on aggregation, and consequently on the electronic and optical properties of nano-assemblies. This work demonstrates a way of controlling the formation of nanoscale structures at the molecular level through the control of noncovalent interactions.     

Identify asthma genes across three phases based on protein–protein interaction network

Asthma is a common inflammatory disease that is generally caused by genetic mutations or environmental factors. Recently, the emerging of omics data provides an alternative way to understand asthma. In this study, the authors present a new framework to detect asthma disease genes based on protein–protein interaction network (PPIN) and gene expression. Specifically, they construct PPINs for different stages of asthma, and detect those interactions occurred in the specific stages. By investigating the proteins in these stage‐specific interactions, they find they are more likely related to asthma, and the functional enrichment analysis indicate that the pathways enriched in the differential interactions are related to the progress of asthma. Moreover, some proteins in the differential interactions have been previously reported to be related to asthma in the literature, implying the usefulness of the proposed approach.Inspec keywords: genomics, proteins, molecular biophysics, lung, pneumodynamics, diseases, genetics, molecule‐molecule reactions, molecule‐molecule collisionsOther keywords: asthma gene identification, three‐phase gene identification, protein–protein interaction network, common inflammatory disease, genetic mutation‐caused disease, environmental factors, asthma‐associated omics data, asthma disease gene detection, PPIN construction, asthma gene expression, asthma stages, stage‐specific interaction proteins, asthma stage‐specific interactions, asthma‐related interactions, functional enrichment analysis, asthma progress‐related differential interactions, differential interaction proteins     

Preparation of water soluble l-arginine capped CdSe/ZnS QDs and their interaction with synthetic DNA: Picosecond-resolved FRET study

We have exchanged TOPO (trioctylphosphine oxide) ligand of CdSe/ZnS core/shell quantum dots (QDs) with an amino acid l-arginine (Arg) at the toluene/water interface and eventually rendered the QDs from toluene to aqueous phase. We have studied the interaction of the water soluble Arg-capped QDs (energy donor) with ethidium (EB) labeled synthetic dodecamer DNA (energy acceptor) using picoseconds resolved Förster resonance energy transfer (FRET) technique. Furthermore, we have applied a model developed by M. Tachiya to understand the kinetics of energy transfer and the distribution of acceptor (EB-DNA) molecules around the donor QDs. Circular dichroism (CD) studies revealed a negligible perturbation in the native B-form structure of the DNA upon interaction with Arg-capped QDs. The melting and the rehybridization pathways of the DNA attached to the QDs have been monitored by the CD which reveals hydrogen bonding is the associative mechanism for interaction between Arg-capped QDs and DNA.     

Theoretical investigations of transport properties of organic solvents in cation-functionalized graphene oxide membranes: Implications for drug delivery

We perform detailed quantum chemical calculations to elucidate the origin and mechanism of the selective permeability of alkali and alkaline earth cation-decorated graphene oxide (M-GO) membranes to organic solvents. The results show that the selectivity is associated mainly with the transport properties of solvents in the membranes, which depends on two regions of the flow path: the sp³ C–O matrix of the GO sheets and the cation at the center of the hexagon rather than the sp² region. According to the delocalization of π states in sp² regions, we propose a design guide for high-quality M-GO membranes. The solvent–cation interaction essentially causes directional transport of molecules in the M-GO membranes under the transmembrane pressure, indicating a site-to-site mechanism. The solvent–sp³ C–O matrix interaction may inhibit molecular transport between two fixed cations by consuming energy. The competition between energy consumption by the solvent–cation interaction and energy expenditure by the solvent–sp³ C–O matrix interaction leads to various transport properties of solvents and thus allows for the selective permeability of the M-GO membranes. Findings from the study are helpful for the future design of multifunctional M-GO macro-membranes as cost-effective solution nanofilters in chemical, biological, and medical applications.

Open image in new window

     

Quantifying protein microstructure and electrostatic effects on the change in Gibbs free energy of binding in immobilized metal affinity chromatography

Electrostatic forces play a major role in maintaining both structural and functional properties of proteins. A major component of protein electrostatics is the interactions between the charged or titratable amino acid residues (e.g., Glu, Lys, and His), whose pK(a) (or the change of the pK(a)) value could be used to study protein electrostatics. Here, we report the study of electrostatic forces through experiments using a well-controlled model protein (T4 lysozyme) and its variants. We generated 10 T4 lysozyme variants, in which the electrostatic environment of the histidine residue was perturbed by altering charged and neutral amino acid residues at various distances from the histidine (probe) residue. The electrostatic perturbations were theoretically quantified by calculating the change in free energy (DeltaDeltaG(E)) using Coulomb's law. On the other hand, immobilized metal affinity chromatography (IMAC) was used to quantify these perturbations in terms of protein binding strength or change in free energy of binding (DeltaDeltaG(B)), which varies from -0.53 to 0.99 kcal/mol. For most of the variants, there is a good correlation (R(2) = 0.97) between the theoretical DeltaDeltaG(E) and experimental DeltaDeltaG(B) values. However, there are three deviant variants, whose histidine residue was found to be involved in site-specific interactions (e.g., ion pair and steric hindrance), which were further investigated by molecular dynamics simulation. This report demonstrates that the electrostatic (DeltaDeltaG(Elec)) and microstructural effects (DeltaDeltaG(Micro)) in a protein can be quantified by IMAC through surface histidine mediated protein-metal ion interaction and that the unique microstructure around a histidine residue can be identified by identifying the abnormal binding behaviors during IMAC.     

An unexpected biomaterial against SARS-CoV-2: Bio-polyphosphate blocks binding of the viral spike to the cell receptor

No other virus after the outbreak of the influenza pandemic of 1918 affected the world’s population as hard as the coronavirus SARS-CoV-2. The identification of effective agents/materials to prevent or treat COVID-19 caused by SARS-CoV-2 is an urgent global need. This review aims to survey novel strategies based on inorganic polyphosphate (polyP), a biologically formed but also synthetically available polyanionic polymeric material, which has the potential of being a potent inhibitor of the SARS-CoV-2 virus-cell-docking machinery. This virus attaches to the host cell surface receptor ACE2 with its receptor binding domain (RBD), which is present at the tips of the viral envelope spike proteins. On the surface of the RBD an unusually conserved cationic groove is exposed, which is composed of basic amino acids (Arg, Lys, and His). This pattern of cationic amino acids, the cationic groove, matches spatially with the anionic polymeric material, with polyP, allowing an electrostatic interaction. In consequence, the interaction between the RBD and ACE2 is potently blocked. PolyP is a physiological inorganic polymer, synthesized by cells and especially enriched in the blood platelets, which releases metabolically useful energy through enzymatic degradation and coupled ADP/ATP formation. In addition, this material upregulates the steady-state-expression of the mucin genes in the epithelial cells. We propose that polyP, with its two antiviral properties (blocking the binding of the virus to the cells and reinforcing the defense barrier against infiltration of the virus) has the potential to be a novel protective/therapeutic anti-COVID-19 agent.     

Production,characterization and optimization of thermoelectric module and investigation of doping effects on thermoelectric performances

The objective of this study is to produce the thermoelectric (TE) module called as a Peltier module or element using new and promising materials that work at high temperature for generation of electricity with thermoelectric energy conversion from waste heat at high temperatures. Peltier modules used commercially nowadays can work at relatively low temperatures and their efficiency increase in proportion to the temperature difference between the surfaces of the modules. They consist of a pair of p- and n-type semiconductor. In this study, calcium cobalt oxide was chosen as a p-type semiconductor whilst zinc oxide was chosen as n-type semiconductor. Pure and aluminum-doped zinc oxide and silver-doped calcium cobalt oxide powders were synthesized via sol–gel processing successfully. The obtained powders were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), fourier transform infrared (FTIR), differential thermal analysis-thermogravimetry (DTA-TG), and scanning electron microscopy (SEM). In addition, the particle size distribution of the powders obtained via sol–gel processing was determined using a particle size analyzer. One and two leg oxide thermo-electric modules consisting of one pair of p-type 0.03 percent silver doped calcium cobalt oxide and n-type 0.02 percent aluminum doped zinc oxide bulks of 25 square millimeter cross-section and 3 millimeter heights were constructed. The thermoelectric module constructed was tested at high temperatures, and compared to other similar oxide modules reported in literature. Ultimately, the thermal stress and alteration of thermal stress depending on the leg length and side length of semiconductors were calculated using the finite element analysis (FEA) model in ANSYS 15.0 software. According to the results of the analysis, TE module was optimized in terms of mechanical behavior.     

Modeling of initial crystallization in the alloys Al–10Ni and Al–5Ni–2.7Y at high undercoolings

Formation and growth of crystallization centers of aluminum in amorphous alloys Al–10Ni and Al–5Ni–2.7Y have been studied by a method of the molecular dynamics. Local radial pair distribution functions were calculated for studying of structure. Growth kinetics of the comparatively large aluminum crystals in the binary system is studied. Latencies of appearance of the first crystallization centre are found. The energies of interatomic interaction averaged locally and also in the bulk of the amorphous phase are determined. It is researched how the size of the crystallization centre influences its structure and the local interaction energy. Formation of icosahedrons and their lifetimes are in consideration.     

Superfluid Boson–Fermion Mixture: Structure Formation and Collective Periodic Motion

Multiple periodic domain formation due to a modulation instability in a boson–fermion mixture superfluid in the unitary regime has been studied. The periodicity of the structure evolves with time. At the early stage of evolution, bosonic domains show the periodic nature, whereas the periodicity in the fermionic (Cooper pair) domains appears at the late stage of evolution. The nature of interatomic interspecies interactions affects the domain formation. In a harmonic trap, the mixture executes an undamped oscillation. The frequency of the oscillation depends on the relative coupling strength between boson–fermion and fermion–fermion. The repulsive boson–fermion interaction reduces the oscillation frequency, whereas the attractive interaction enhances the frequency significantly.     

Diketopyrrolopyrrole (DPP)‐Based Donor–Acceptor Polymers for Selective Dispersion of Large‐Diameter Semiconducting Carbon Nanotubes

Low‐bandgap diketopyrrolopyrrole (DPP)‐based polymers are used for the selective dispersion of semiconducting single‐walled carbon nanotubes (s‐SWCNTs). Through rational molecular design to tune the polymer–SWCNT interactions, highly selective dispersions of s‐SWCNTs with diameters mainly around 1.5 nm are achieved. The influences of the polymer alkyl side‐chain substitution (i.e., branched vs linear side chains) on the dispersing yield and selectivity of s‐SWCNTs are investigated. Introducing linear alkyl side chains allows increased polymer–SWCNT interactions through close π–π stacking and improved C–H–π interactions. This work demonstrates that polymer side‐chain engineering is an effective method to modulate the polymer–SWCNT interactions and thereby affecting both critical parameters in dispersing yield and selectivity. Using these sorted s‐SWCNTs, high‐performance SWCNT network thin‐film transistors are fabricated. The solution‐deposited s‐SWCNT transistors yield simultaneously high mobilities of 41.2 cm² V^?1 s^?1 and high on/off ratios of greater than 10⁴. In summary, low‐bandgap DPP donor–acceptor polymers are a promising class of polymers for selective dispersion of large‐diameter s‐SWCNTs.