Emiliano Laudadio

One notable issue in low terahertz (THz) applications is to achieve sources with higher output power than the state of the art. One possible solution to the foregoing problem is to amplify the electromagnetic field emitted by already accessible THz generators. Here, we study the quantum Čerenkov effect as a possible explanation for low-THz amplification, which has been found experimentally elsewhere. Specifically, the emission of surface plasmons from traveling electrons in mono-dimensional graphene, mediated by charge–field interaction, is shown to provide in-plane electromagnetic radiation down to THz and mm-wave frequencies. We focus on a structure consisting of a graphene layer between metal electrodes, which enhance the field confinement and lead to a linearization of the plasmon dispersion in the frequency domain. When compared to a non-confined plasmonic radiation, the above-mentioned configuration shows emission rates ten times larger, which make it promising for THz amplification.

Glaucoma, a major ocular neuropathy originating from a progressive degeneration of retinal ganglion cells, is often associated with increased intraocular pressure (IOP). Daily IOP fluctuations are physiologically influenced by the antioxidant and signaling activities of melatonin. This endogenous modulator has limited employment in treating altered IOP disorders due to its low stability and bioavailability. The search for low-toxic compounds as potential melatonin agonists with higher stability and bioavailability than melatonin itself could start only from knowing the molecular basis of melatonergic activity. Thus, using a computational approach, we studied the melatonin binding toward its natural macromolecular targets, namely melatonin receptors 1 (MT1) and 2 (MT2), both involved in IOP signaling regulation. Besides, agomelatine, a melatonin-derivative agonist and, at the same time, an atypical antidepressant, was also included in the study due to its powerful IOP-lowering effects. For both ligands, we evaluated both stability and ligand positioning inside the orthosteric site of MTs, mapping the main molecular interactions responsible for receptor activation. Affinity values in terms of free binding energy (ΔGbind) were calculated for the selected poses of the chosen compounds after stabilization through a dynamic molecular docking protocol. The results were compared with experimental in vivo effects, showing a higher potency and more durable effect for agomelatine with respect to melatonin, which could be ascribed both to its higher affinity for hMT2 and to its additional activity as an antagonist for the serotonin receptor 5-HT2c, in agreement with the in silico results.