Two co-existing and opposing mechanisms of proton transfer in one-dimensional open-end water chains.

The proton transport in one-dimensional (1D) confined water chains has been extensively studied as a model for ion channels in cell membrane and fuel cell. However, the mechanistic understanding of the proton transfer (PT) process in 1D water chains remains incomplete. In this study, we demonstrate that the two limiting structures of the hydrated excess proton, H5O2+ (Zundel) and H3O+ (linear H7O3+), undergo a change in dominance as the water chain grows, causing two co-existing and opposing PT mechanisms. Specifically, H5O2+ is stable in the middle of the chain, whereas H3O+ serves as a transition state (TS). Except for this region, H3O+ is stabilized while H5O2+ serves as a TS. The interaction analysis shows that the electrostatic interaction plays a crucial role in the difference in PT mechanisms. Our work fills a knowledge gap between the various PT mechanisms reported in bulk water and long 1D water chains, contributing to a deeper understanding of biological ion channels at the atomic level.

Histone Modifications in NAFLD: Mechanisms and Potential Therapy.

Nonalcoholic fatty liver disease (NAFLD) is a progressive condition that encompasses a spectrum of liver disorders, beginning with the simple steatosis, progressing to nonalcoholic steatohepatitis (NASH), and possibly leading to more severe diseases, including liver cirrhosis and hepatocellular carcinoma (HCC). In recent years, the prevalence of NAFLD has increased due to a shift towards energy-dense dietary patterns and a sedentary lifestyle. NAFLD is also strongly associated with metabolic disorders such as obesity and hyperlipidemia. The progression of NAFLD could be influenced by a variety of factors, such as diet, genetic factors, and even epigenetic factors. In contrast to genetic factors, epigenetic factors, including histone modifications, exhibit dynamic and reversible features. Therefore, the epigenetic regulation of the initiation and progression of NAFLD is one of the directions under intensive investigation in terms of pathogenic mechanisms and possible therapeutic interventions. This review aims to discuss the possible mechanisms and the crucial role of histone modifications in the framework of epigenetic regulation in NAFLD, which may provide potential therapeutic targets and a scientific basis for the treatment of NAFLD.

Dual-Band and Multi-State Polarization Conversion Using aTerahertz Symmetry-Breaking Metadevice.

We numerically and experimentally demonstrate a terahertz metadevice consisting of split-ring resonators (SRRs) present within square metallic rings. This device can function as a dual-band polarization converter by breaking the symmetry of SRRs. Under x-polarized incidence, the metastructure is able to convert linearly polarized (LP) light into a left-hand circular-polarized (LCP) wave. Intriguingly, under y-polarized incidence, frequency-dependent conversion from LP to LCP and right-hand circular-polarized (RCP) states can be achieved at different frequencies. Furthermore, reconfigurable LCP-to-LP and RCP-to-LP switching can be simulated by integrating the device with patterned graphene and changing its Fermi energy. This dual-band and multi-state polarization control provides an alternative solution to developing compact and multifunctional components in the terahertz regime.

Out-of-plane resonances in terahertz photonic crystal slabs modulated by optical pumping.

This paper describes detailed optical-pump-terahertz-probe studies of two-dimensional photonic crystal slabs for propagation perpendicular to the slabs. When the slabs are excited by an 800 nm pump pulse and the effect of shielding by photocarriers is removed, we find that the decaying tail in the transmitted terahertz radiation is strikingly enhanced. The photocarriers weaken guided resonances, but they also greatly enhance the excitation efficiency of guided resonances and the ability of the guided resonances to transfer energy back to the radiation field. This increases the resonance-assisted contribution to transmitted field. The photoinduced resonant extremes agree well with the Fano model.

[Study on the THz spectra of tyrosine].

Terahertz time-domain spectroscopy (TDS) has been used to study the spectral properties of tyrosine at room temperature. The terahertz spectra of sample were observed. The result shows that the sample has the spectral response in terahertz spectral range, a fact demonstrating that the terahertz spectra of tyrosine could be used to study the molecular structure and vibration of sample. Two absorption peaks were found at 0.23 and 2.46 THz respectively for the first time. The corresponding theoretical spectra were given by using HF and DFT methods for both tyrosine monomer and dimmer. The difference between the theoretical and experimental results was analyzed in detail. The origin of the observed absorption at 0.23 THz was assigned to the wagging of the two tyrosine molecules linked by hydrogen bond.