The catalytic triad Cys145–His41–Asp187 of SARS-CoV-2 Mpro plays an important role in the activation of the PF-07321332 covalent inhibitor.

We study a planar metamaterial supporting electromagnetically-induced transparency (EIT)-like effect by exploiting the coupling between bright and quasi-dark eigenmodes. The specific design of such a metamaterial consists of a cut-wire (CW) and a single-gap split-ring resonator (SRR).From the numerical and the analytical results we demonstrate that the response of SRR, which is weakly excited by external electric field, is mitigated to be a quasi-dark eigenmode in the presence of strongly radiative CW. This result suggests more relaxed conditions for the realization of devices utilizing the EIT-like effects in metamaterial, and thereby widens the possibilities for many different structural implementations.

We studied both experimentally and theoretically the influence of the distance between adjacent cut-wire-pair layers on the magnetic and the electric resonances in the microwave-frequency regime. Besides the dependence on the separation between cut-wire pairs, along the electric-field direction, the electric resonance strongly depends on the distance between cut-wire-pair layers, while the magnetic resonance is almost unchanged. This contrast can be understood by the difference in the distribution of induced-charge density and in the direction of the induced current between the electric and magnetic resonances. A simple model is proposed to simulate our experimental results and the simulation results are in good agreement with the experiment. This result provides important information in obtaining left-handed behavior when the cut-wire pairs are combined with the continuous wire.

It is well known that, together with the plasma behavior of continuous wires, the use of cut-wire pair as a metamagnetic component is to drive the negative permeability in the left-handed combined structure. In this study, we have investigated a strange left-handed transmission in a metamaterial consisting of only conventional cut-wire pair structure without additional adjustment. It is shown that the observed left-handed behavior, which occurs at a frequency three times higher than that for the combined structure, originates from the fundamental negative permittivity provided by the symmetric resonant mode and a negative permeability by the third-order asymmetric resonance. Our results would simplify extremely the fabricating procedure, especially, for terahertz regime as well as reveal many possibilities to design optical devices based on the electromagnetic responses of cut-wire structure.

Polymer nanocomposites based on polyaniline (PANi) and graphene nanosheets (GNS) modified with poly(sodium 4-styrensulfonate) (PSS-GNS) were prepared, and their structure and properties were investigated by atomic force microscopy (AFM), scanning electron microscopy (SEM), UV-vis spectroscopy, ATR-IR spectroscopy, X-ray diffraction, elemental analysis, thermogravimetric analysis (TGA) and electrical conductivity measurements. The results revealed that for the PANi/PSS-GNS nanocomposites, the disordered structure of PSS-GNS was fully destroyed and PSS-GNS exists in the form of a single GNS or stacked PSS-GNS elements in a PANi matrix. PSS-GNS was partly covered by PANi due to hydrogen bonding that occurs between the PSS-GNS and PANi. By incorporating PSS-GNS, the electrical conductivity of PANi increased linearly from 0.84 S/cm for neat PANi to 4.96 S/cm for a PANi/PSS-GNS (5%) nanocomposite. The thermal stability of the PANi was also improved significantly to approximately 100 o C by the nanocomposite.