Doubling Förster Resonance Energy Transfer Efficiency in Proteins with Extrinsic Thioamide Probes: Implications for Thiomodified Nucleobases

Designing a potential protein–ligand pair is pivotal, not only to track the protein structure dynamics, but also to assist in an atomistic understanding of drug delivery. Herein, the potential of a small model thioamide probe being used to study albumin proteins is reported. By monitoring the Förster resonance energy transfer (FRET) dynamics with the help of fluorescence spectroscopic techniques, a twofold enhancement in the FRET efficiency of 2-thiopyridone (2TPY), relative to that of its amide analogue, is observed. Molecular dynamics simulations depict the relative position of the free energy minimum to be quite stable in the case of 2TPY through noncovalent interactions with sulfur, which help to enhance the FRET efficiency. Finally, its application is shown by pairing thiouracils with protein. It is found that the site-selective sulfur atom substitution approach and noncovalent interactions with sulfur can substantially enhance the FRET efficiency, which could be a potential avenue to explore in the design of FRET probes to study the structure and dynamics of biomolecules.     

Molecules relevant for organic photovoltaics: a range-separated density functional study

Accurate determination of both fundamental and optical gap is necessary for designing molecules relevant for organic photovoltaics. Here, we study how range-separated density functionals reproduce frontier orbital energies, HOMO (highest occupied molecular orbital)–LUMO (lowest unoccupied molecular orbital) gaps, and optical gaps for molecules relevant for organic photovoltaics. In this study, we consider 12 different range-separated density functional for computing HOMO energy, HOMO–LUMO gap, and optical gap which are compared with available experimental and reported GW values. We found that the reproduction of desired photovoltaic properties primarily depend on range separation parameter. Moreover, the tested functionals are comparable with OT-BNL functional.     

Polymerization of Methyl Methacrylate: Kinetics of the Reaction Initiated by the Mn(III)-1,2-Propanediol Redox System

Kinetics of polymerization of methyl methacrylate initiated by Mn³⁺/1,2-propanedlol has been investigated in aqueous sulfuric acid at the temperature range of 25–35°C. The rate of polymerization (R_p) and the rate of manganic ion disappearance (-R_Mn) have been computed. The effects of organic solvents, certain cationic and anionic detergents, added electrolytes on the initial rate of polymerization, and maximum conversion have been examined. Depending on the kinetic results, a reaction scheme has been suggested involving the formation of a complex between Mn³⁺ and the alcohol, which subsequently decomposed in an unimolecular step to generate the initiating free-radical which initiates polymerization and termination of the growing polymer chain by metal ion.     

Perchloric Acid-Catalyzed Synthesis of 9-Aryl Xanthenes-9H-3,6-diol and 1,3,6,8-Tetraol in Water

Efficient syntheses of xanthenes have been described using a catalytic amount of perchloric acid in water. The high temperature and lengthy reaction time normally required for formation of xanthenes derivatives are not necessary when using a catalytic amount of perchloric acid. The method is relatively inexpensive, easily available, nonvolatile, nonexplosive, and thermally robust to catalyze the reaction at 80 °C by simple heating with good to excellent yields. The advantages of the reaction involve simple reaction protocol, simple workup, and improved synthesis in the presence of perchloric acid as catalyst.     

Calculations of dynamic dipole polarizabilities of Li and Na atoms in debye plasma using the model potential technique

The effects of Debye plasma on the frequency‐dependent polarizabilities of Li and Na atoms are investigated using symplectic algorithm within the framework of the pseudostate summation technique. Dynamic dipole polarizabilities of Li (2s ²S) and Na(3s ²S) as functions of scaled number density of the plasma electrons for arbitrary plasma temperature are presented. Screening effects on the resonance frequencies are also presented. In free‐atomic cases, our calculated results are comparable with the reported theoretical and experimental predictions. © 2012 Wiley Periodicals, Inc.     

Comparative Antioxidant Study of Stem and Stem Induced Callus of Phyllanthus fraternus Webster—An Important Antiviral and Hepatoprotective Plant

Phyllanthus fraternus is widely used in the cure of various liver diseases and possess antiviral properties especially against hepatitis virus. In the present study, evaluation of the antioxidant activity of stem and calli induced from stem has been done by different assays. Extraction was done by standard method in water and ethanol. Total antioxidant capacity was measured by 1, 1-diphenyl-2-picrylhydrazyl free radical scavenging method. Lipid peroxidation was measured in terms of thiobarbituric acid-reactive substances (TBARS) by using egg yolk homogenates as lipid-rich media, and superoxide radical scavenging activity was measured using riboflavin–light–nitro blue tetrazolium assay. Reducing power was determined on the basis of Fe³⁺–Fe²⁺ transformation in the presence of the extract. In addition to the antioxidant activity, polyphenolic compounds like total phenolics and flavonoids were also measured by spectroscopic method. Results showed that the ethanolic extract of stem is more potent in antioxidant activity than its aqueous extract and ethanolic extract of calli. A significant correlation between antioxidant capacity and polyphenolic content and reducing potential was observed, indicating that phenolic compounds and reducers present in extract are major contributors to the antioxidant potential. Thus, this plant extract could be used as a potent natural antioxidant.     

Modeling and analysis of a marine plankton system with nutrient recycling and diffusion

This article describes a nutrient‐phytoplankton‐zooplankton system with nutrient recycling in the presence of toxicity. We have studied the dynamical behavior of the system with delayed nutrient recycling in the first part of the article. Uniform persistent of the system is examined. In the second part of the article, we have incorporated diffusion of the plankton population to the system and dynamical behavior of the system is analyzed with instantaneous nutrient recycling. The condition of the diffusion driven instability is obtained. The conditions for the occurrence of Hopf and Turing bifurcation critical line in a spatial domain are derived. Variation of the system with small periodicity of diffusive coefficient has been studied. Stability condition of the plankton system subject to the periodic diffusion coefficient of the zooplankton is derived. It is observed that nutrient‐phytoplankton‐zooplankton interactions are very complex and situation specific. Moreover, we have obtained different exciting results, ranging from stable situation to cyclic oscillatory behavior may occur under different favorable conditions, which may give some insights for predictive management. © 2014 Wiley Periodicals, Inc. Complexity 21: 229–241, 2015     

Influence of sputter power on structural and electrical properties of TiO2 films for Al/TiO2/Si gate capacitors

Titanium dioxide (TiO₂) thin films were deposited onto p‐Si substrates held at room temperature by reactive Direct Current (DC) magnetron sputtering at various sputter powers in the range 80–200 W. The as‐deposited TiO₂ films were annealed at a temperature of 1023 K. The post‐annealed films were characterized for crystallographic structure, chemical binding configuration, surface morphology and optical absorption. The electrical and dielectric properties of Al/TiO₂/p‐Si structure were determined from the capacitance–voltage and current–voltage characteristics. X‐ray diffraction studies confirmed that the as‐deposited films were amorphous in nature. After post‐annealing at 1023 K, the films formed at lower powers exhibited anatase phase, where as those deposited at sputter powers > 160 W showed the mixed anatase and rutile phases of TiO₂. The surface morphology of the films varied significantly with the increase of sputter power. The electrical and dielectric properties on the air‐annealed Al/TiO₂/p‐Si structures were studied. The effect of sputter power on the electrical and dielectric characteristics of the structure of Al/TiO₂/p‐Si (metal‐insulator‐semiconductor) was systematically investigated. Copyright © 2014 John Wiley & Sons, Ltd.     

Metal Complexes of Singly,Doubly and Triply Linked Porphyrins and Corroles: An Insight into the Physicochemical Properties

Metal complexes of multi-porphyrins and multi-corroles are unique systems that display a host of extremely interesting properties. Availability of free meso and β positions allow formation of different types of directly linked bis-porphyrins giving rise to intriguing optical and electronic properties. While the fields of metalloporphyrin and corroles monomer have seen exponential growth in the last decades, the chemistry of metal complexes of bis-porphyrins and bis-corroles remain rather underexplored. Therefore, the impact of covalent linkages on the optical, electronic, (spectro)electrochemical, magnetic and electrocatalytic activities of metal complexes of bis-porphyrins and -corroles has been summarized in this review article. This article shows that despite the (still) somewhat difficult synthetic access to these molecules, their extremely exciting properties do make a strong case for pursuing research on these classes of compounds.     

Tuning the antioxidant property of potential calixdrug calix[4]tyrosol: role of aza and thia linkages

Structural Chemistry - Calix[4]arenes are the most renowned and widely studied calix[n]arenes, which are established to have quite a few biological (e.g., antibacterial, antifungal, antioxidant,...