Influence of Acidity and Oxidant Concentration on the Nanostructures and Electrochemical Performance of Polyaniline during Fast Microwave-Assisted Chemical Polymerization

Polyaniline (PANI), a typical conducting polymer, has attracted great interest as an electrode material. A series of PANIs were prepared through fast microwave-assisted chemical oxidative polymerization with varying HCl and APS concentrations here. It was found that the microwave synthesized PANIs had ~4 times higher for the yields and 7~10 times higher for the electrical conductivity in comparison to PANI samples prepared using conventional method. PANI nanosheets could easily be fabricated in weakly acidic solution due to their oligomeric structure, which contained flat phenazine rings. By contrast, linear PANI chains produced in highly acidic solutions formed nanofibers. The APS concentration did not significantly affect the molecular structures of PANIs under the conditions here. However, increasing the concentration of APS produced nanofibers with shorter branches, which may be due to secondary nucleation during chain growth resulting from increases in active initiation centers. The electrical conductivity and electrochemical performance of PANIs were both improved with increasing HCl and APS concentrations. Improvements due to increases in HCl concentration may be attributed to additions in conjugation length and enrichment of doping levels, while improvements due to increases in APS concentration could be attributed to the increased crystallinity of PANI, which facilitates ion transport

Influence of Annealing on Chain Entanglement and Molecular Dynamics in Weak Dynamic Asymmetry Polymer Blends

The influence of annealing above the glass transition temperature (<i>T</i>_g) on chain entanglement and molecular dynamics of solution-cast poly­(methyl methacrylate)/poly­(styrene-co-maleic anhydride) (PMMA/SMA) blends was investigated via a combination of dynamic rheological measurement and broadband dielectric spectroscopy. Chain entanglement density increases when the annealing temperature and/or time increases, resulting from the increased efficiency of chain packing and entanglement recovery. The results of the annealing treatment without cooling revealed that the increase of the entanglement density occurred during the annealing process instead of the subsequent cooling procedure. Annealing above <i>T</i>_g exerts a profound effect on segmental motion, including the transition temperature and dynamics. Namely, <i>T</i>_g shifts to higher temperatures and the relaxation time (τ_max) increases due to the increased entanglement density and decreased molecular mobility. Either <i>T</i>_g or τ_max approaches an equilibrium value gradually, corresponding to the equilibrium entanglement density that might be obtained through the theoretical predictions. However, no obvious distribution broadening is observed due to the unchanged heterogeneous dynamics. Furthermore, side group rotational motion could be freely achieved without overcoming the chain entanglement resistance. Hence, neither the dynamics nor the distribution width of the subglass relaxation (β- and γ-relaxation) processes is affected by chain entanglement resulting from annealing, indicating that the local environment of the segments is unchanged

Prediction of Toxoplasma gondii virulence factor ROP18 competitive inhibitors by virtual screening

Abstract Background Rhoptry protein 18 (ROP18) is a key virulence factor of Toxoplasma gondii. The host’s immune responses mediated by immune-related GTPases (IRGs) could be blocked by ROP18’s kinase activity. ROP18 also interacts with various substrates, such as activating transcription factor 6 beta (ATF6β) and affects multiple physiological functions within host cells, thereby inducing intense virulence. In this study, competitive inhibitors targeted to ROP18 were subjected to virtual screening based on the principle of structure-based drug design (SBDD). Methods The preparation of the ROP18 structure was conducted using the “Structure Prepare” function of Molecular Operating Environment (MOE) software. The ATP-binding pocket was selected as the starting point for virtual screening. Construction of the pharmacophore model used Extended Hückel Theory (EHT) half-quantitative measurement and construction, as well as the characteristics of Type I kinase inhibitors. The pharmacophore model of ROP18 was imported into the Specs database for small molecule similarity screening using EHT pharmacophore measurement. Hit compounds were selected using the functions of London dG and generalized-born volume integral/weighted surface area (GBVI/WSA) scoring. The top 100 hits were analyzed by molecular docking and structure activity relationships (SAR) analysis. Results The final pharmacophore comprised three typical characteristics: three hydrogen bond acceptors/donors, two ring aromatic features occupying the hydrophobic core, and one cation group feature targeted to the terminus of ATP. A total of 1314 hit compounds analogous to ROP18 pharmacophore were passed through the Specs. After two rounds of docking, 25 out of 100 hits were identified as belonging to two main scaffold types: phthalimide ring structure, thiazole ring and styrene structure. Additionally, the screen also identified 13 inhibitors with distinct scaffold types. The docking models and SAR analysis demonstrated that these hits could engage in multiple hydrogen bonds, salt bridges halogen bonds, and hydrophobic interactions with ROP18, and para-position halo substituents on the benzene ring may enhance their affinity scoring. Conclusions A pharmacophore against the ROP18 ATP-binding pocket was successfully constructed, and 25 representative inhibitors from 15 scaffold clusters were screened using the Specs database. Our results provide useful scaffold types for the chemical inhibition of ROP18 or alternative conformations to develop new anti-toxoplasmosis drug leads