Spike Proteins of SARS-CoV and SARS-CoV-2 Utilize Different Mechanisms to Bind With Human ACE2

The ongoing outbreak of COVID-19 has been a serious threat to human health worldwide. The virus SARS-CoV-2 initiates its infection to the human body via the interaction of its spike (S) protein with the human Angiotensin-Converting Enzyme 2 (ACE2) of the host cells. Therefore, understanding the fundamental mechanisms of how SARS-CoV-2 S protein receptor binding domain (RBD) binds to ACE2 is highly demanded for developing treatments for COVID-19. Here we implemented multi-scale computational approaches to study the binding mechanisms of human ACE2 and S proteins of both SARS-CoV and SARS-CoV-2. Electrostatic features, including electrostatic potential, electric field lines, and electrostatic forces of SARS-CoV and SARS-CoV-2 were calculated and compared in detail. The results demonstrate that SARS-CoV and SARS-CoV-2 S proteins are both attractive to ACE2 by electrostatic forces even at different distances. However, the residues contributing to the electrostatic features are quite different due to the mutations between SARS-CoV S protein and SARS-CoV-2 S protein. Such differences are analyzed comprehensively. Compared to SARS-CoV, the SARS-CoV-2 binds with ACE2 using a more robust strategy: The electric field line related residues are distributed quite differently, which results in a more robust binding strategy of SARS-CoV-2. Also, SARS-CoV-2 has a higher electric field line density than that of SARS-CoV, which indicates stronger interaction between SARS-CoV-2 and ACE2, compared to that of SARS-CoV. Key residues involved in salt bridges and hydrogen bonds are identified in this study, which may help the future drug design against COVID-19.

An Improved Normalized Model of Electrical Capacitance Tomography

Electrical capacitance tomography (ECT) technology is a process tomography, which is based on medical CT technology and develops together with computer and sensor technology. The measured capacitances by ECT system are usually normalized at the high and low permittivity for image. Parallel normalization model is commonly used during normalization process, which assumes the distribution of materials in parallel. And thus, the normalized capacitance is a linear function of measured capacitance. The usage of series normalization model results in the normalized capacitance as a nonlinear function of measured capacitance. The research on parallel, series normalization model and hybrid normalization model. In this paper, we propose a method based on the center electric field line to determine the model weighting factor for the hybrid normalization model. The simulation and static test results show that the reconstructed image quality is improved obviously by the hybrid normalization model based on the center electric field line.

The Flashover Phenomena due to Water Drops on Insulating Surface under DC Electric Field

This paper presents the flashover between the electrodes conducted the current by the water drop on insulating surfaces. It causes ageing to the insulator and leads to deterioration when the insulator is used for over years. In the experiments, epoxy resin with the water drop is tested by using direct current until flashover of 70 kV. Besides that, the effect of the water volume, the number of the water drop and the water types - tap and aqua water on flashover are investigated. The flashover of tap water grows faster when increases the volume of water drop. The flashover of aqua water does not depend on the volume of water drop. The deformation and elongate of water drop is in the direction of electric field line. The results lead to protect the damage of insulator caused by the humidity and the loss of their efficiency insulators.

Fabrication of Microfibrous Patterns via Electrospinning

Using patterned conductive and insulating collection devices, fibrous patterns from polyvinyl pyrrolidone were fabricated by electrospinning. Considering that the electrospun fibers tend to deposit along the direction of electric field line, when conductive patterned template is used as collector during electrospinning, the as-spun fibers tend to assemble onto the conductive grids, whereas the dropping fibers prefer to avoid insulation grid by concentrating toward the surface of the Al foil when an insulating grid based on Al foil is used as collector.

Line Patterning with Microparticles at Different Positions in a Single Device Based on Negative Dielectrophoresis

We report on control of line pattern positioning with particles fabricated by negative dielectrophoresis (n-DEP) using the applied intensity and phase of an AC electric field. Line patterns were fabricated in a microfluidic device consisting of upper conductive indium-tin-oxide (ITO) substrates and lower ITOinterdigitated microband array (IDA) electrodes used as the template. A 6-µm-diameter polystyrene particles suspension was introduced into the device between upper ITO and the bottom ITO-IDA substrate. An AC electric signal of a typically 20 peak-to-peak voltage and 1.0 MHz was then applied to upper ITO and bands on lower IDA, resulting in the formation of line patterns with low electric-field gradient regions. AC voltage was applied to bands A and B on lower IDA with the opposite phase and the same frequency and intensity. When the signal identical to band A was applied to upper ITO, particles were aligned above band A because relatively lower electric fields were produced in these regions. In contrast, the application of a signal identical to band B formed line patterns with particles aligned above band B due to the generation of a strong electric field between band A and upper ITO and the disappearance of the strong electric field between band B and upper ITO. The decrease in applied intensity to upper ITO shifted the accumulated position of particles to the center between bands A and B because of the balance of electric fields generated between band A or B and upper ITO. We thus fabricated line patterns with particles at desired positions in the fluidic device.