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The present study was conducted in order to study the detailed molecular mechanism of tumor necrosis factor (TNF)-α in chronic obstructive pulmonary disease (COPD). The rats were treated with cigarette smoke (CS) and lipopolysaccharide (LPS) to establish the COPD model. Next, the changes in lung injury in COPD rats with TNF-α knockdown was tested. Meanwhile, the regulation of TNF-α on MAPK pathway and its downstream molecules (SOCS3/TRAF1) was determined by western blotting. On this basis, the activation of MAPK and inhibition of SOCS3/TRAF1 was also examined. Subsequently, the lung function was tested with the plethysmograph, the cells of bronchoalveolar lavage fluid was counted and classified. Furthermore, lung tissue sections were stained with hematoxylin and eosin to verify whether the treatment of MAPK pathway and downstream molecules affected the effect of TNF-α knockdown on COPD. The present study showed that TNF-α knockdown could alleviate the decrease in the function and inflammatory injury of the lungs of rats with COPD. Western blot analysis verified that TNF-α knockdown could inhibit the activation of MAPK pathway and increase the expression of SOCS3/TRAF1. The following experimental results showed that the relief of lung injury caused by TNF-α knockdown could be deteriorated by activating MAPK pathway. It was also found that the symptom of COPD was decreased following transfection with sh-TNF-α but worsened by SOCS3/TRAF1 knockdown. Overall, TNF-α knockdown inhibited the activation of MAPK pathway and increased the expression of SOCS3/TRAF1, thus delaying the process of COPD.

Structural and dynamic properties of ions confined in nanoslits are crucial to understand the fundamental mechanism underlying a wide range of chemical and biological phenomena. K+ and Cl– show similar ion mobilities in a bulk aqueous solution, whereas they exhibit a remarkable difference when transporting through an angstrom-scale channel. Our molecular dynamics simulations uncover that such discrepancy originates from the subtle differences in their hydration structures and preferable locations across the channel. Opposite charge causes different water dipolar orientations around ions, mediating the distance and tribological interactions between hydrated ions and channel’s walls. Hydrated Cl– ions experience a remarkable larger friction force inside the channel and consequently a smaller mobility compared with K+ ions. This charge asymmetry mechanism becomes dominant when the channel size approaches the molecular scale, which takes responsibility for the delicate distinction between dynamic transport be...

There has been long-standing academic interest in the study of ion transport in nanochannel systems, owing to its vast implications in understanding the nature of numerous environmental, biological and chemical processes. Here, we investigate ion transport through two-dimensional slits using molecular dynamics simulations. These slits with angstrom-scale height dimensions can be realistically replicated in the simulation, which leads to direct comparisons between simulations and experiments. In particular, this new confining geometry allows the size exclusion effect to be unambiguously decoupled from other mechanisms. As the slit size approaches the ultimate scale, dehydration at the entry impedes the ionic conductance significantly, and even induces a complete ion rejection. We demonstrate that energy barriers required to accomplish the ion permeation can be theoretically connected to the partial dehydration process. The proposed model is further validated by simulations. Our results offer insights into the atomistic details of ion permeation, which may also shed light on developing effective ways for water filtration and desalination.

In this work, the ion transport of K+ and Li+ through angstrom-scale pores was thoroughly investigated using molecular dynamics (MD) simulation. Despite of their similar sizes, anomalously selective behaviors were observed. Our MD simulations found that the selectivities through two kinds of pores with diameters of 4 A and 5 A show an opposite preference on K+ or Li+ respectively under certain applied voltage. We demonstrated that the exchange of hydration shell with surrounding water molecules plays an important role in the ion mobility. Higher exchange rate equivalently reduces the apparent friction of the hydrated ion during its migration, thus increases the ion mobility. The interactions between ions and the pore edge also contribute to the ion mobility. Our results provide insights into the atomic scale details of ion transport process. Based on these findings, the applied voltage and pore size can be used to actively control the selectivity of K+/Li+ ions.

Adsorption and diffusion of lithium-ion on and between graphene layers are investigated by an analytical model, employing a pairwise potential, which can be approximated by the Lennard–Jones potential to express the interaction between lithium-ion and each carbon atom of graphene. The equilibrium position and binding energy of lithium-ion at three particular adsorption sites (hollow, bridge, and top) are calculated, and the adsorption stability is discussed. The results show that hollow site is the most stable adsorption site, and top site is the most unstable. The adsorption and diffusion of lithium-ion on different sizes of monolayer graphene are investigated and proved to be size and edge dependent. Moreover, lithium-ion would rather diffuse on the surface of graphene than through a hexagonal carbon ring to the other side no matter what the graphene sheet size is. In addition, two kinds of vacancy defects in graphene are considered to study the diffusion of lithium-ion. The vacancy defect can improve energy barrier, and if a vacancy defect is big enough, lithium-ion migrating through the vacancy area from one layer to another is feasible. The possible applications of present study include rechargeable lithium-ion graphene battery and Li storage in carbon material.

"Shuttle effect" of lithium polysulfides (LiPS) leads to a poor performance and a short cycle life of the Li-S battery, thus limiting their practical application. We demonstrate here that after coating polypropylene (PP) separator with a continuous monolayer graphene, the shuttle effect can be significantly suppressed by limiting the passage of long-chain LiPS. The graphene/PP separator can be further modified by sealing the big holes or pores on graphene with in situ polymerized nylon-66 via an interfacial polymerization reaction between diamine and adipoyl chloride supplied by the aqueous and oil phase, respectively, from each side of the membrane. With this engineered membrane, an initial specific capacity of 1128.4 mAh g-1 at 0.05C is achieved after test in a coin cell, higher than that of 983.2 mAh g-1 with pristine PP, along with increased Coulombic efficiency from 96.0 to 99.9% and enhanced cycling durability. Molecular dynamics simulations attest that the nanopores with appropriate size and structure are effective in acting as a "sieve" to selectively allow only Li+ ions to pass through but prevent LiPS from migrating to the anode, consequently alleviating the shuttle effect. Our method provides a facile solution toward the mitigated shuttle effect and eventually contributes to the high performance of Li-S battery.

Theoretical investigations are made on adsorption and diffusion of atoms/ions on graphene surface based on an analytical continuous model. An atom/ion interacts with every carbon atom of graphene through a pairwise potential which can be approximated by the Lennard-Jones (L-J) potential. Using the Fourier expansion of the interaction potential, the total interaction energy between the adsorption atom/ion and a monolayer graphene is derived. The energy-distance relationships in the normal and lateral directions for varied atoms/ions, including gold atom (Au), platinum atom (Pt), manganese ion (Mn2+), sodium ion (Na1+), and lithium-ion (Li1+), on monolayer graphene surface are analyzed. The equilibrium position and binding energy of the atoms/ions at three particular adsorption sites (hollow, bridge, and top) are calculated, and the adsorption stability is discussed. The results show that H-site is the most stable adsorption site, which is in agreement with the results of other literatures. What is more, the periodic interaction energy and interaction forces of lithium-ion diffusing along specific paths on graphene surface are also obtained and analyzed. The minimum energy barrier for diffusion is calculated. The possible applications of present study include drug delivery system (DDS), atomic scale friction, rechargeable lithium-ion graphene battery, and energy storage in carbon materials.

Recent research progress shows that graphene exhibits distinct adhesion and friction behaviors. In the paper, the static and dynamic analyses of a diamond tip sliding on suspended graphene surface are conducted via theoretical and numerical research methods, and the adhesion and friction properties between them are investigated. The analytical expression of interaction potential between a diamond tip and graphene surface is derived based on the interatomic pairwise potential, and then, the lateral and normal interaction forces are calculated. The equilibrium heights and adhesion energy of the diamond tip are calculated on three particular sites of graphene surface. The influence of vertical distance between the tip and graphene surface is studied on the maximum static frictional force and initial velocity of tip. What is more, the influence of scanning velocity and damping are also analyzed on the frictional force and dynamic behaviors of the scanning tip, and the “stick-slip” phenomenon is observed and discussed by the numerical calculation.