Kaicheng Wang

Liquid–liquid phase separation (LLPS) of RNA drives the formation of membraneless organelles, and its dysregulation is closely linked to major human diseases, including cancer, neurodegenerative disorders, and various rare genetic diseases. Current strategies for modulating LLPS often require the introduction of exogenous molecules or specific genetic modifications. Here, coarse-grained molecular dynamics (CGMD) simulations suggest that terahertz (THz) oscillatory fields may influence the condensation of pathogenic G4C2 RNA repeats under the simulated conditions. Oscillatory fields at 10 THz and 37.3 THz are shown to effectively counteract salt-induced condensate dissolution. At the molecular level, THz oscillatory fields are associated with reduced phosphate–sodium contacts at low ionic strengths and with faster water diffusion in the hydration layer at higher salt levels. These changes correlate with an increase in stable intermolecular contacts and a more compact RNA state, suggesting a field-driven shift in the balance of interactions. These findings provide a conceptual and mechanistic basis for understanding how oscillatory fields may influence biomolecular condensation, establishing a microscopic framework for using external variable fields to manipulate biomolecular assemblies.

The voltage-gated calcium influxes modulated with terahertz Gaussian pulse is presented in this paper, and temperature rise is evaluated to monitor the terahertz thermal effects involved in the modulation. From the numerical results, inhibition effect on voltage-gated calcium influx because of the loss of the influx from electric drift is transparently revealed in the modulation with terahertz Gaussian pulse. And the inhibition effect becomes significant reflected by considerable reduction in voltage-gated calcium influx as the irradiated amplitude is raised intense enough. Compared to the terahertz sinusoidal wave, Gaussian pulse reduces the inhibition effect dramatically. The decrease in the increment of intracellular calcium concentration with the irradiated amplitude due to the inhibition effect is substantially relieved by the modulation of the calcium influx with terahertz Gaussian pulse. The thermal analyses reveal that the modulation is non-thermal effect. Meanwhile, to raise the intracellular calcium concentration to a same amount by means of the voltage-gated calcium influx, application of terahertz Gaussian pulse induces much less concurrent temperature rise than application of terahertz sinusoidal wave of the same amplitude that is intense enough to cause the inhibition effect. Additionally, terahertz Gaussian pulse irradiation remains the dependence of the increment of the calcium concentration on the irradiated time duration and frequency in terahertz sinusoidal wave irradiation. These numerical results lay the theoretical basis for the modulation of voltage-gated calcium fluxes with terahertz Gaussian pulse and for further potential clinical applications of terahertz Gaussian pulse.

Local oriented intense electric fields play a vital role in biochemical reactions such as enzyme catalysis. Many researchers have gradually applied external oriented electric fields to control specific chemical reactions. The rapidly developing intense field of terahertz technology can provide a strong enough oriented electric field with specific polarization direction on a sub-picosecond timescale, which matches the timescale and intensity requirements for affecting specific ultrafast chemical reactions. Inspired by this, this paper theoretically studied the full quantum model of the proton transfer process in DNA base pair hydrogen bonds induced by intense terahertz radiation (ITR) with a sub-picosecond-oriented electric field through simulation based on density functional theory (DFT) and the Schrodinger equation. The result shows that the ITR with an electric field intensity up to 10 GV m⁻¹ in a specific polarization direction can precisely control the proton transfer process in the base pair hydrogen bonds. Based on flexible optical methods, the ITR is expected to go beyond the traditional techniques for applying strong electric fields to chemical systems through solid electrodes and become a catalyst for controlling chemical reactions or a scalpel to manipulate molecular structures.

This paper simulates Ca2+ transmembrane transport through voltage-gated Ca2+ channels in response to terahertz electromagnetic irradiation. The active transport of Ca2+ ions is taken into considerations in the Ca2+ transport. Temperature variations due to terahertz electromagnetic loss in physiological medium are simulated. The electromagnetic interaction between terahertz fields and physiological mobile ions at the cellular level is deduced from relativistic electrodynamics. It shows that effects of 0.1 ~ 3 THz electromagnetic fields on cell mobile ions are primarily due to effects of electric fields, and effects of magnetic fields at the cellular level are insignificant. In addition, numerical simulation reveals that terahertz irradiation causes vibration of membrane potential, which is able to activate voltage-gated Ca2+ channels. Besides, bioeffects of terahertz frequency, irradiation duration and electric intensity on the increment of intracellular Ca2+ concentration due to activation of voltage-gated Ca2+ channels are revealed. Meanwhile, numerical results show that temperature rises are inconsequential in the case of different irradiation parameters, indicating the non-thermal bioeffects of voltage-gated Ca2+ transmembrane transport due to terahertz irradiation. Furthermore, the results also reveal that thermal bioeffect can be significant if the irradiation duration is raised long enough for high-dose terahertz irradiation. The numerical simulations lay the basis for understanding the bioeffects of terahertz irradiation on Ca2+ transmembrane transport and pave the way for further exploration in modulation of intracellular Ca2+ concentration with terahertz electromagnetic wave.

Terahertz quantized vibrational modes and quasi-one-dimensional terahertz phononic band gap in hydrocarbon tails of phospholipids are revealed through vibration calculation based on the ab initio density functional theory (DFT). We obtain the correlation between vibrational modes and frequencies. The phononic band gap in linear hydrocarbon chains provides a perspective in the interpretation of biochemical phenomena related to biological membranes, such as the photosynthetic energy transfer and the electron transport chain in the inner mitochondrial membrane.

An electron optical system with long-range low emission current density electron gun and H-plane double-slit coupling input-output RF coupler are studied for 340GHz sheet beam staggered double vane traveling wave tube (TWT). The long-range sheet beam electron gun can reduce the difficulties in assembling and adjusting of the whole magnetic system. Low emission current density can reduce the processing difficulty and improve the life of the electron gun. The bandwidth of the microwave circuits with H-plane double-slit input and output couplers is so broad that can approach 45GHz. Taking the high frequency loss of copper into account, the beam-wave interaction simulation shows that the whole design provides 14.6W of output power and 31.6dB gain at 340GHz.