Photo- and electrochemical redox behavior of cyclometalated Ru(II) complexes having a 3-phenylbenzo[b][1,6]naphthyridine ligand

Cyclometalated Ru(II) complexes having a 3-phenylbenzo[b][1,6]naphthyridine (phbn) ligand have been synthesized and characterized by spectroscopic methods. The photo- and electrochemical redox behavior of the complexes are demonstrated. Complex [Ru(phbn)(bpy)(2)]PF(6) ([1]PF(6)) readily undergoes proton coupled two electron reduction by chemical, electrochemical, and photochemical methods to generate [Ru(phbnHH)(bpy)(2)]PF(6) ([1HH]PF(6)). The photochemical oxidation of [1HH]PF(6) was also observed in presence of p-chloranil.     

Antimicrobial Activity of MgB2 Powders Produced via Reactive Liquid Infiltration Method

We report for the first time on the antimicrobial activity of MgB₂ powders produced via the Reactive Liquid Infiltration (RLI) process. Samples with MgB₂ wt.% ranging from 2% to 99% were obtained and characterized, observing different levels of grain aggregation and of impurity phases. Their antimicrobial activity was tested against Staphylococcus aureus ATCC BAA 1026, Enterococcus faecalis ATCC 29212, Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, and Candida albicans ATCC 10231. A general correlation is observed between the antibacterial activity and the MgB₂ wt.%, but the sample microstructure also appears to be very important. RLI-MgB₂ powders show better performances compared to commercial powders against microbial strains in the planktonic form, and their activity against biofilms is also very similar.     

Anticancer therapeutic efficacy of biogenic Am-ZnO nanoparticles on 2D and 3D tumor models

The present study fabricates biogenic zinc oxide nanoparticles (ZnO NPs) with the aqueous leaf extract of Annona muricata (Am) plant collected from semi-evergreen forests of Odisha, India. The synthesized Am-ZnO NPs were physicochemically characterized. The ultraviolet/visible spectrum showed the maximum optical absorbance of Am-ZnO NPs at 355 nm. High-resolution transmission electron microscopy analysis presented the nearly spherical shape of Am-ZnO NPs with an average particle size of 80 nm. The net surface charge and hydrodynamic size of Am-ZnO NPs were measured to be ～?2.59 mV and ～417 nm, respectively. Am-ZnO NPs were found to be biocompatible and hemocompatible nature. Furthermore, Am-ZnO NPs displayed strong anticancer effects on both 2D and 3D tumor models. We observed a dose-dependent toxicity on both A549 and MOLT4 cells and observed a size reduction in the A549 tumor spheroids. Subsequently, we observed a depolarization in mitochondrial membrane potential of Am-ZnO NP–treated cancer cells leading to the apoptosis induction in cancer cells.     

Synthesis,spectral, and structural investigation of [ML(NO3)2]: M = Co,Ni, Cu; L = N-(2-pyridylethyl)pyridine-2-methylketimine

Synthesis and structural characterization of distorted pentagonal bipyramidal Co(II), pseudo-octahedral Ni(II) and Cu(II) complexes of the type [ML(NO₃)₂], {L = N-(2-pyridylethyl)pyridine-2-methylketimine} are reported. Characterization includes elemental analysis, spectral, magnetism, and X-ray crystallographic studies. In case of cobalt (1) both the nitrates coordinate in bidentate fashion resulting overall distorted pentagonal bipyramidal geometry. In nickel (2) and copper (3) complexes, bivalent metal ion is coordinated by the three nitrogen atoms of the tridentate L with two pyridine-N occupying trans positions and amongst the two nitrates one coordinates in a bidentate fashion while other adopts a monodentate fashion. All the complexes exhibit d–d transitions in the visible region. Complex 1 is high-spin in nature and the X-band EPR spectra of 1, and 3 at room temperature and 77 K are reported.     

Periodic solutions for an equation governing dynamics of a renewable resource subjected to Allee effects

In this article the minimum number of positive periodic solutions admitted by a non-autonomous scalar differential equation is estimated. This result is employed to find the minimum number of positive periodic solutions admitted by a model representing dynamics of a renewable resource that is subjected to Allee effects in a seasonally varying environment. The Allee effect refers to a decrease in population growth rate at low population densities. Leggett–Williams multiple fixed point theorem is used to establish the existence of positive periodic solutions.     

Three periodic solutions for a nonlinear first order functional differential equation

This paper is concerned with the existence of three positive T-periodic solutions of the first order functional differential equations of the form

x^′(t)=a(t)x(t)-λb(t)f(t,x(h(t))),     

Prediction of the structures of helical membrane proteins based on a minimum unfavorable contacts approach

An understanding of structure–function relationships of membrane proteins continues to be a challenging problem, owing to the difficulty in obtaining their structures experimentally. This study suggests a method for modeling membrane protein structures that can be used to generate a reliable initial conformation prior to the use of other approaches for sampling conformations. It involves optimizing the orientation of hydrophilic residues so as to minimize unfavorable contacts with the hydrophobic tails of the lipid bilayer. Starting with the optimized initial conformation for three different proteins modeled based on this method, two independent approaches have been used for sampling the conformational space of the proteins. Both approaches are able to predict structures reasonably close to experimental structures, indicating that the initial structure enables the sampling of conformations that are close to the native structure. Possible improvements in the method for making it broadly applicable to helical membrane proteins are discussed. © 2015 Wiley Periodicals, Inc.     

Studies on Aqueous Polymerization of Acryionitriie Initiated by Ce(IV)-Amino Acid Redox Pair

Aqueous polymerization of acryionitriie initiated by the Ce(IV)-glycine redox pair was studied at 35°C under nitrogen. The rate of polymerization, R_p, was found to be approximately proportional to the square of the monomer concentration within the range of 0.140s–1.268 M. R was also found to increase with glycine concentration in the interval 0.1 to 0.4 M and decrease with cerie ion concentration. The activation energy was estimated to be 25.8 kcal/mol. A suitable kinetic scheme was proposed and explained in the light of these experimental findings. The end-group in the polymer was characterized by IR spectra, and the average molecular weight of the polymer was found to be 84,100.     

Evidence for positive Darwinian selection on the hepcidin gene of Perciform and Pleuronectiform fishes

Hepcidin is a small cysteine-rich peptide that plays an important role in antimicrobial activity and in maintaining iron homeostasis in vertebrates. Here we report on the underlying mechanism that maintains high sequence diversities among the hepcidin-like variants of perciform and pleuronectiform fishes. In contrast to mammals, maximum likelihood-based codon substitution analyses revealed that positive Darwinian selection (nonsynonymous to synonymous substitution, ω > 1) is the likely cause of accelerated rate of amino acid substitutions in the hepcidin mature peptide region of these fishes. Comparison of models incorporating positive selection (ω > 1) at certain sites with models not incorporating positive selection (ω < 1) failed to reject (p = 0) the evidence of positive selection among the codon sites of percifom and pleuronectiform hepcidin. The adaptive evolution of this peptide in perciform and pleuronectiform fishes might be directed by pathogens when the host is exposed to new habitats/environments.