Using Constellation Pharmacology to Characterize a Novel α-Conotoxin from Conus ateralbus.

The venom of cone snails has been proven to be a rich source of bioactive peptides that target a variety of ion channels and receptors. α-Conotoxins (αCtx) interact with nicotinic acetylcholine receptors (nAChRs) and are powerful tools for investigating the structure and function of the various nAChR subtypes. By studying how conotoxins interact with nAChRs, we can improve our understanding of these receptors, leading to new insights into neurological diseases associated with nAChRs. Here, we describe the discovery and characterization of a novel conotoxin from Conus ateralbus, αCtx-AtIA, which has an amino acid sequence homologous to the well-described αCtx-PeIA, but with a different selectivity profile towards nAChRs. We tested the synthetic αCtx-AtIA using the calcium imaging-based Constellation Pharmacology assay on mouse DRG neurons and found that αCtx-AtIA significantly inhibited ACh-induced calcium influx in the presence of an α7 positive allosteric modulator, PNU-120596 (PNU). However, αCtx-AtIA did not display any activity in the absence of PNU. These findings were further validated using two-electrode voltage clamp electrophysiology performed on oocytes overexpressing mouse α3ß4, α6/α3ß4 and α7 nAChRs subtypes. We observed that αCtx-AtIA displayed no or low potency in blocking α3ß4 and α6/α3ß4 receptors, respectively, but improved potency and selectivity to block α7 nAChRs when compared with αCtx-PeIA. Through the synthesis of two additional analogs of αCtx-AtIA and subsequent characterization using Constellation Pharmacology, we were able to identify residue Trp18 as a major contributor to the activity of the peptide.

A Lower Dose of Infection Generates a Better Long-Term Immune Response against Toxoplasma gondii.

Toxoplasma gondii, an obligate intracellular pathogen, induces a strong immune response in the infected host. In the encephalitis model of infection, long-term protective immunity is mediated by CD8 T cells, with the CD4 T cell population providing important help. Most of the immune studies have used a 10- to 20-cyst dose of T. gondii, which leads to T cell dysfunctionality during the late phase of chronic infection and increases the chances of reactivation. In the current study, we compared the immune response of mice orally infected with either 2 or 10 cysts of T. gondii. During the acute phase, we demonstrate that the lower dose of infection generates a reduced number of CD4 and CD8 T cells, but the frequency of functional CD4 or CD8 T cells is similar in animals infected with two different doses. However, Ag-experienced T cells (both CD4 and CD8) are better maintained in lower dose-infected mice at 8 wk postinfection, with an increase number functional cells that exhibit lower multiple inhibitory receptor expression. In addition to better long-term T cell immunity, animals infected with a lower dose display reduced inflammation manifested by lesser Ag-specific T cell and cytokine responses during the very early stage of the acute infection. Our studies suggest a previously unappreciated role of dose-dependent early programming/imprinting of the long-term CD4/CD8 T cell response during T. gondii infection. These observations point to the need for an in-depth analysis of how early events shape long-term immunity against this pathogen.

Modulating the Optical Band Gap of Small Semiconducting Two-Dimensional Materials by Conjugated Polymers.

Ultra-high-resolution optical microscopic techniques are used to measure the reflectance and photoluminescence (PL) spectrum of individual monolayered MoS2 of dimensions below 200 × 200 nm, while placed on top of a thin film conjugated polymer (CP). p-type and n-type CPs such as poly(3-hexylthiophene-2,5-diyl) (P3HT) and [6,6]-phenyl C61 butyric acid methyl ester (PCBM), respectively, modified the optical band gap of the MoS2 sheet differently. However, the optical band gap is decreased after integration with P3HT, while it is increased after being combined with PCBM. The acceptable reason for the modification of the band gap of MoS2 by CPs is the generation of interlayer excitons (ILE) at their interface. The optical band gap of MoS2 is further changed by introducing an inert polymer spacer of different thickness to separate MoS2 from the CP. This is attributed to the reduction of the efficiency of excitonic interactions and lowering the exciton binding energy, which is induced by the increase of the dielectric function at the CP-MoS2 interface. No sign of electron injection to the conduction band of MoS2 after integration with P3HT or PCBM, as no significant shift of the A1' Raman band of MoS2 was measured on top of CPs, which is sensitive to the electron injection.

Modifying the Band Gap of Semiconducting Two-Dimensional Materials by Polymer Assembly into Different Structures.

Polyethylene glycol (PEG) assembled on the surface of two-dimensional tungsten disulfide (WS2) into a limited number of nanoislands (NIs), nanoshells (NSs), and granular nanoparticulates (GNPs) depending on its chain length. NI assemblies showed a nonmeasurable shift of photoluminescence (PL) and the A and B absorption peaks of WS2. This confirmed that the electronic doping by thiol is not effective. The PEG NS assembly displayed a smaller red shift of the PL and a slight decrease of the energy difference between the A and B absorption peaks of WS2. However, increasing the dielectric function on the surface of WS2 has a small influence on their optical properties. The PEG NP assembly on WS2 exhibited a significant red shift of the PL spectrum and a large decrease of the energy difference between A and B absorption peaks. Deforming the WS2 sheet by the PEG NP assembly decreased the orbital coupling and lowered the electronic direct band gap significantly. Raman bands of WS2 are shifted to a higher frequency on improving its mechanical strength after the PEG assembly.