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Shiv Nadar University

(SoNS) School of Natural Sciences

The interaction of phospholipids with the peripheral membrane proteins like spectrin is important not only to understand the various physiological functions of cells, but also to gain insight into the mechanism involved in the self-assembly of polymer-like long chain molecules at the soft surfaces and interfaces. The lipid head-group specificity of adsorption of spectrin to supported phopsholipid bilayer model membranes has been investigated using the X-ray reflectivity (XRR) technique. Model lipid bilayers composed of phosphatidylcholine (PC) and phosphatidylethanolamine (PE) head groups have been prepared on a soft polymer cushion and the XRR measurements have been carried out from the bilayers immersed in a water bath using high-energy synchrotron X-rays. Our results suggest that in PC-based membranes the spectrin chains form a uniform layer on top of the bilayer with their chains lying on the membrane surface, while in PE-based membranes with relatively smaller head groups, the spectrin chains are attached only through a few possible binding sites with the rest of the part projected out of the membrane surface. In addition, the reflectivity profiles reveal the penetration of spectrin polypeptide chains through the PE bilayer in its fluid phase. Pressure-area isotherm measurements on Langmuir monolayers also support similar observations on the adsorption of spectrin molecules to the membranes composed of PC and PE. The observed results were explained using a qualitative model based on the ion-mediated protein interaction in the PC-based membrane. © CopyrightEPLA, 2017.

World University root node

Physics

Differential adsorption of a membrane skeletal protein, spectrin, in phospholipid membranes

<p>This work describes a simple wet chemical synthesis of iron oxide (Fe3O4) nanoparticles (NPs) capped with terephthalic acid (TA) and their application for the individual detection of Hg(II), Pb(II) and Cd(II) ions as well as simultaneous and selective detection of Hg(II), Pb(II) and Cd(II) ions by electrochemical approach. Terephthalic acid capped Fe3O4 NPs were first characterized by cyclic voltammetry (CV) using redox couples Fe(CN)63&nbsp;−/4&nbsp;−, thereafter square wave anodic stripping voltammetry (SWASV) was utilized for the detection of Hg(II), Pb(II) and Cd(II) ions. Optimization of experimental parameters such as deposition time, deposition potential and pH value of the electrolyte towards electrochemical detection of target heavy metal ions was also carried out in SWASV method. Under optimized experimental conditions limit of detection (LOD) values for individual analysis of Hg(II), Pb(II) and Cd(II) ions were found to be 0.1, 0.05&nbsp;μM and 0.01&nbsp;μM respectively, whereas the LOD values for the simultaneous analysis of Hg(II), Pb(II) and Cd(II) ions were found to be 0.3&nbsp;μM, 0.04&nbsp;μM and 0.2&nbsp;μM respectively. © 2017 Elsevier B.V.</p>

Journal of Electroanalytical Chemistry

Terephthalic acid capped iron oxide nanoparticles for sensitive electrochemical detection of heavy metal ions in water

This chapter explores the utility of cardanol as a potential feedstock for the synthesis of benzoxazine monomers and polymers. Cardanol is a renewable phenolic compound obtained from the plant Anacardium occidentale L. Commercially it is produced as cashew nut shell liquid (CNSL) as a byproduct of cashew nut processing. It is currently under exploration as a valuable phenolic reagent in benzoxazine monomers and polymers. Cardanol-based benzoxazines are attractive monomers due to their sustainable aspect, opportunities for solventless synthesis, and processing. To date, Cardanol monomers have primarily been utilized for adhesive and composite applications, but they are ideal candidates for a variety of other applications, which need further exploration. © 2017 Elsevier Inc. All rights reserved.

Chemistry

Advanced and Emerging Polybenzoxazine Science and Technology

Cardanol-Based Benzoxazines and Their Applications

Carbonyl-carbonyl n→πinteractions where a lone pair (n) of the oxygen atom of a carbonyl group is delocalized over the πorbital of a nearby carbonyl group have attracted a lot of attention in recent years due to their ability to affect the 3D structure of small molecules, polyesters, peptides, and proteins. In this paper, we report the discovery of a "reciprocal" carbonyl-carbonyl interaction with substantial back and forth n→πand π→πelectron delocalization between neighboring carbonyl groups. We have carried out experimental studies, analyses of crystallographic databases and theoretical calculations to show the presence of this interaction in both small molecules and proteins. In proteins, these interactions are primarily found in polyproline II (PPII) helices. As PPII are the most abundant secondary structures in unfolded proteins, we propose that these local interactions may have implications in protein folding. © 2017 The Author(s).

Fulltext

Nature Communications

Reciprocal carbonyl-carbonyl interactions in small molecules and proteins

In this paper, we revisit a result by Jurg et al. (Linear Algebra Appl 141:61–74, 1990) where the necessary and sufficient condition for a bimatrix game to be weakly completely mixed is given. We present an alternate proof of this result using linear complementarity approach. We extend this result to a generalization of bimatrix game introduced by Gowda and Sznajder (Int J Game Theory 25:1–12, 1996) via a generalization of linear complementarity problem introduced by Cottle and Dantzig (J Comb Theory 8:79–90, 1970). We further study completely mixed switching controller stochastic game (in which transition structure is a natural generalization of the single controller games) and extend the results obtained by Filar (Proc Am Math Soc 95:585–594, 1985) for completely mixed single controller stochastic game to completely mixed switching controller stochastic game. A numerical method is proposed to compute a completely mixed strategy for a switching controller stochastic game. © 2016, Springer Science+Business Media New York.

Mathematics

Dynamic Games and Applications

Completely Mixed Strategies for Generalized Bimatrix and Switching Controller Stochastic Game

Human telomeric G-quadruplex DNA stabilization has emerged as an exciting novel approach for anticancer drug development. In the present study, we have designed and synthesized three C2-symmetric bisubstituted bisbenzimidazole naphthalenediimide (NDI) ligands, ALI-C3, BBZ-ARO, and BBZ-AROCH2, which stabilize human telomeric G-quadruplex DNA with high affinity. Herein, we have studied the binding affinities and thermodynamic contributions of each of these molecules with G-quadruplex DNA and compared the same to those of the parent NDI analogue, BMSG-SH-3. Results of fluorescence resonance energy transfer and surface plasmon resonance demonstrate that these ligands have a higher affinity for G4-DNA over duplex DNA and induce the formation of a G-quadruplex. The binding equilibrium constants obtained from the microcalorimetry studies of BBZ-ARO, ALI-C3, and BBZ-AROCH2 were 8.47, 6.35, and 3.41 μM, respectively, with h-telo 22-mer quadruplex. These showed 10 and 100 times lower binding affinity with h-telo 12-mer and duplex DNA quadruplexes, respectively. Analysis of the thermodynamic parameters obtained from the microcalorimetry study suggests that interactions were most favorable for BBZ-ARO among all of the synthesized compounds. The ΔGfree obtained from molecular mechanics Poisson-Boltzmann surface area calculations of molecular dynamics (MD) simulation studies suggest that BBZ-ARO interacted strongly with G4-DNA. MD simulation results showed the highest hydrogen bond occupancy and van der Waals interactions were between the side chains of BBZ-ARO and the DNA grooves. A significant inhibition of telomerase activity (IC50 = 4.56 μM) and induced apoptosis in cancer cell lines by BBZ-ARO suggest that this molecule has the potential to be developed as an anticancer agent. © 2017 American Chemical Society.

ACS Omega

Naphthalenediimide-Linked Bisbenzimidazole Derivatives as Telomeric G-Quadruplex-Stabilizing Ligands with Improved Anticancer Activity

Verhandlungen der Deutschen Physikalischen Gesellschaft

Spin liquid behavior in the triangular lattice iridate Ba3InIr2O9

The extent of alloying and the alloy composition, which are crucial in determining the activity and selectivity of bimetallic catalysts, were studied in porous silica encapsulated AgPd catalysts using XRD, HRTEM and HAADF-STEM. Water-dispersible ligand protected Pd ultra-small clusters and Ag nanoparticles of three different sizes were used as the precursors. The high reactivity of Pd ultra-small clusters enhanced the alloying of larger Ag nanoparticles to some extent. Encapsulation appeared to have minimised the sintering of the resultant nanoparticles. The earlier suggestions of the role of d-band positions with respect to adsorption energies holds good for the AgPd system and alloying enhances the activity. Alloy with the composition of Ag50Pd50 was found to be the most active with the reaction rate enhanced two fold compared to that in other compositions. Other factors like particle size and sinter-resistance also played important roles in enhancing the activity of these catalysts. © 2017 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.

New Journal of Chemistry

Understanding alloy structure and composition in sinter-resistant AgPd@SiO2 encapsulated catalysts and their effect on catalytic properties

A robust economic approach to N-(quinazoline-4-yl)sulfonamides was developed and synthesized different aryl, hetero aryl, alkyl and cyclopropyl sulfonamides in excellent yields. All the compounds were evaluated for cytotoxic affinity to SKOV3, DU145, THP1, U937, and COLO205 cell lines. Interesting to find that the bulkiness of substituent at C-2 position of quinazoline forces the molecule to flip around in order to bind in the active site, when compared to the binding preference of previously known quinazoline compounds. Among the 21 compounds synthesized 2b, 2d, 2e, 2h, 2i, 3c, 3d, 3f, 3g and 3h found to be active on all the cell lines tested with IC50 values &lt;10 µg/mL. Performed docking simulations to understand the binding preference of various C-2 substituted quinazoline sulfonamides. © 2017 Elsevier Ltd

Bioorganic and Medicinal Chemistry Letters

Synthesis and biological evaluation of novel quinazoline-sulfonamides as anti-cancer agents

Ionic liquids (ILs) are potential candidates for new antimicrobials due to their tunable antibacterial and antifungal properties that are required to keep pace with the growing challenge of bacterial resistance. To a great extent their antimicrobial actions are related to the interactions of ILs with cell membranes. Here, we report the effects of ILs on the nanoscopic dynamics and phase behaviour of a dimyristoylphosphatidylcholine (DMPC) membrane, a model cell membrane, as studied using neutron scattering techniques. Two prototypical imidazolium-based ILs 1-butyl-3-methylimidazolium tetrafluoroborate (BMIM[BF4]) and 1-decyl-3-methylimidazolium tetrafluoroborate (DMIM[BF4]), which differ only in terms of the alkyl chain length of cations, have been used for the present study. Fixed Elastic Window Scan (FEWS) shows that the incorporation of ILs affects the phase behaviour of the phospholipid membrane significantly and the transition from a solid gel to a fluid phase shifts to lower temperature. This is found to be consistent with our differential scanning calorimetry measurements. DMIM[BF4], which has a longer alkyl chain cation, affects the phase behaviour more strongly in comparison to BMIM[BF4]. The pressure-area isotherms of the DMPC monolayer measured at the air-water interface show that in the presence of ILs, isotherms shift towards higher area-per lipid molecule. DMIM[BF4] is found to shift the isotherm to a greater extent compared to BMIM[BF4]. Quasielastic neutron scattering (QENS) data show that both ILs act as a plasticizer, which enhances the fluidity of the membrane. DMIM[BF4] is found to be a stronger plasticizing agent in comparison to BMIM[BF4] that has a cation with a shorter alkyl chain. The incorporation of DMIM[BF4] enhances not only the long range lateral motion but also the localised internal motion of the lipids. On the other hand, BMIM[BF4] acts weakly in comparison to DMIM[BF4] and mainly alters the localised internal motion of the lipids. Any subtle change in the dynamical properties of the membrane can profoundly affect the stability of the cell. Hence, the dominant effect of the IL with the longer chain length on the dynamics of the phospholipid membrane might be correlated with its cytotoxic activity. QENS data analysis has provided a quantitative description of the effects of the two imidazolium-based ILs on the dynamical and phase behaviour of the model cell membrane, which is essential for a detailed understanding of their action mechanism. © 2017 The Royal Society of Chemistry.