Simulation on the Physical Process of Neural Electromagnetic Signal Generation Based on a Simple but Functional Bionic Na+ Channel

The physical processes occurring at open Na+ channels in neural fibers are essential for understanding the nature of neural signals and the mechanism by which the signals are generated and transmitted along nerves. However, there is less generally accepted description of these physical processes. We studied changes in the transmembrane ionic flux and the resulting two types of electromagnetic signals by simulating the Na+ transport across a bionic nanochannel model simplified from voltage-gated Na+ channels. Results show that the Na+ flux can reach a steady state in approximately 10 ns owing to the dynamic equilibrium of Na+ ions concentration difference between the both sides of membrane. After characterizing the spectrum and transmission of these two electromagnetic signals, the low-frequency transmembrane electric field is regarded as the physical quantity transmitting in waveguide-like lipid dielectric layer and triggering the neighboring voltage-gated channels. Factors influencing the Na+ flux transport are also studied. The impact of the Na+ concentration gradient is found higher than that of the initial transmembrane potential on the Na+ transport rate, and introducing the surface-negative charge in the upper third channel could increase the transmembrane Na+ current. This work can be further studied by improving the simulation model; however, the current work helps to better understand the electrical functions of voltage-gated ion channels in neural systems.

The Diverse Physiological Functions of Mechanically Activated Ion Channels in Mammals

Many aspects of mammalian physiology are mechanically regulated. One set of molecules that can mediate mechanotransduction are the mechanically activated ion channels. These ionotropic force sensors are directly activated by mechanical inputs, resulting in ionic flux across the plasma membrane. While there has been much research focus on the role of mechanically activated ion channels in touch sensation and hearing, recent data have highlighted the broad expression pattern of these molecules in mammalian cells. Disruption of mechanically activated channels has been shown to impact ( a) the development of mechanoresponsive structures, ( b) acute mechanical sensing, and ( c) mechanically driven homeostatic maintenance in multiple tissue types. The diversity of processes impacted by these molecules highlights the importance of mechanically activated ion channels in mammalian physiology. Expected final online publication date for the Annual Review of Physiology, Volume 84 is February 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

A Salt-Signaling Network Involving Ethylene, Extracellular ATP, Hydrogen Peroxide, and Calcium Mediates K+/Na+ Homeostasis in Arabidopsis

This work aimed at investigating the interactive effects of salt-signaling molecules, i.e., ethylene, extracellular ATP (eATP), H2O2, and cytosolic Ca2+ ([Ca2+]cyt), on the regulation of K+/Na+ homeostasis in Arabidopsisthaliana. The presence of eATP shortened Col-0 hypocotyl length under no-salt conditions. Moreover, eATP decreased relative electrolyte leakage and lengthened root length significantly in salt-treated Col-0 plants but had no obvious effects on the ethylene-insensitive mutants etr1-1 and ein3-1eil1-1. Steady-state ionic flux kinetics showed that exogenous 1-aminocyclopropane-1-carboxylic acid (ACC, an ethylene precursor) and eATP-Na2 (an eATP donor) significantly increased Na+ extrusion and suppressed K+ loss during short-term NaCl treatment. Moreover, ACC remarkably raised the fluorescence intensity of salt-elicited H2O2 and cytosolic Ca2+. Our qPCR data revealed that during 12 h of NaCl stress, application of ACC increased the expression of AtSOS1 and AtAHA1, which encode the plasma membrane (PM) Na+/H+ antiporters (SOS1) and H+-ATPase (H+ pumps), respectively. In addition, eATP markedly increased the transcription of AtEIN3, AtEIL1, and AtETR1, and ACC treatment of Col-0 roots under NaCl stress conditions caused upregulation of AtRbohF and AtSOS2/3, which directly contribute to the H2O2 and Ca2+ signaling pathways, respectively. Briefly, ethylene was triggered by eATP, a novel upstream signaling component, which then activated and strengthened the H2O2 and Ca2+ signaling pathways to maintain K+/Na+ homeostasis under salinity.

Understanding the role of ionic flux on the polarity of the exposed surfaces of ZnO

The role of ionic flux in controlling the polarity of the surfaces of ZnO was evaluated, both experimentally and theoretically.

Molar Volume Mismatch: A Malefactor for Irregular Metallic Electrodeposition in Solid Electrolytes

Regularizing metallic electrodeposition has been a long-standing challenge in energy storage. Leveraging mechanical stresses, solid ion conductors have been proposed to stabilize the evolving interface. Paradoxically softer electrodepositing metals are often found to form penetration fronts under the hypothesized stable conditions. We find that mechanical contributions to energy of the interacting species (i.e., metal and cation) relate to respective molar volumes. The stresses at the electrodepositing interface are correlated, and consequently, localized deposition is energetically favored for larger cationic molar volumes. Electrolyte stresses cause a stress-driven ionic flux away from compressed locations, which proves to be a stabilizing influence. Stability is found to be nonlinearly related to electrolyte stiffness. Material complexities such as interphases, interlayer, and grain boundaries are also examined to proffer guidelines for a stabilized growth.