Piecewise linear differential systems without equilibria produce limit cycles?

In this article, we study the planar piecewise differential systems formed by two linear differential systems separated by a straight line, such that both linear differential have no equilibria, neither real nor virtual. When the piecewise differential system is continuous, we show that the system has no limit cycles. But when the piecewise differential system is discontinuous, we show that it can have at most one limit cycle.     

Druggable hot spots in trypanothione reductase: novel insights and opportunities for drug discovery revealed by DRUGpy

Journal of Computer-Aided Molecular Design - Assessment of target druggability guided by search and characterization of hot spots is a pivotal step in early stages of drug-discovery. The raw output...     

Rational Design,Synthesis and Evaluation of Indole Nitrogen Hybrids as Photosystem II Inhibitors

We report the synthesis of twelve indole derivatives bearing nitro or amide groups via Fischer indole methodology followed by reduction/acetylation and amidation reactions. After thorough characterization, these indoles were subjected to a number of studies in order to evaluate their bioactive potential as photosynthesis and plant growth inhibitors. Firstly, these molecular hybrids were evaluated as photosystem II (PSII) inhibitors through chlorophyll a (Chl a) fluorescence measurement. In this study, 6-chloro-8-nitro-2,3,4,9-tetrahydro-1H-carbazole ( 15a ) and 5-chloro-2,3-dimethyl-7-nitro-1H-indole ( 15b ) showed the best results by reducing the phenomenological parameters of reaction centers ABS/RC, TR₀/RC and ET₀/RC of PSII. Electron chain blockage by these compounds may lead to diminished ATP synthesis and CO₂ fixation which interrupt the plant development. The compounds 15a and 15b both act as postemergent herbicides, reducing the dry biomass of Ipomoea grandifolia and Senna alata weeds by an average of 40% and 37%, respectively, corroborating the fluorescence results. Additionally, the molecular docking study revealed that the presence of strong electron-withdrawing groups at the indole phenyl ring is important for the ligand’s interaction with the binding pocket of protein D1 on PSII. The optimization of these molecular features is the goal of our research group in further understanding and development of new potent herbicides.     

Dinitriles Bearing AIE‐Active Moieties: Synthesis,E/Z Isomerization,and Fluorescence Properties

Dinitriles bearing aggregation‐induced emission (AIE)‐active moieties [tetraphenylethylene (TPE) or diphenylphenanthrene (DPP)] were prepared. Compounds 4 (TPE‐linked) and 8 (DPP‐linked) showed considerably redshifted emission resulting from their large Stokes shifts and also strong fluorescence in the aggregated and solid states. Pure E and Z stereoisomers of both dinitriles were easily separated, and their isomerization equilibria and fluorescence properties were investigated. In addition to their pronounced AIEE behavior, 4 and 8 also showed various reversible chromic responses to external stimuli, namely, solvato‐, piezo‐, vapo‐, and thermochromism, which make them potential candidates for smart materials.     

Hydrazine‐Assisted Liquid Exfoliation of MoS2 for Catalytic Hydrodeoxygenation of 4‐Methylphenol

A simple but effective method to exfoliate bulk MoS₂ in a range of solvents is presented for the preparation of colloid flakes consisted of one to a few molecular layers by application of ultrasonic treatment in N₂H₄. Their high yield in solution and exposure of more active surface sites allows the synthesis of corresponding solid catalysts with remarkably high activity in hydrodeoxygenation of 4‐methylphenol and this method can also be applied to other two dimensional materials.