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Shiv Nadar University

(SoNS) School of Natural Sciences

Carbohybrids are an important class of molecules which exhibit diverse biological activities and are present as structural motifs in many natural products. Two series of new triazole linked N-glycosides of coumarins and quinolones (n = 27) were efficiently synthesized starting from 1-azido-2,3,4,6-tetra-O-acetyl β-d-glucose and 1-azido-2,3,4,6-tetra-O-acetyl β-d-galactose reacting with various 4-O-propargyl coumarins and 4-O-propargyl quinolones in shorter reaction time (30 min) under microwave assisted conditions. Anticancer activity of these newly synthesized triazole linked N-glycosides of coumarins and quinolones was determined in detail through cellular assays against MCF-7 (breast cancer cell line), HepG2 (liver cancer cell line), HCT-116 (colon cancer cell line) and Huh-7.5 cell lines. The selected library member displayed low micromolar (IC50 10.97 μM) and selective toxicity against the breast cancer cell line (MCF-7). Mechanistic studies showed that the anticancer activity of the active compound was because of the generation of reactive oxygen species (ROS). This journal is © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.

Life Sciences

Fulltext

New Journal of Chemistry

Synthesis of new triazole linked carbohybrids with ROS-mediated toxicity in breast cancer

ConspectusThis Account addresses the catalytic cycle of the enzyme cytochrome P450 (CYP450) as a prototypical biological machine with automatic features. CYP450 is a nanomachine that uses dioxygen and two reducing and two proton equivalents to oxidize a plethora of molecules (so-called substrates) as a means of supplying bio-organisms with essential molecules (e.g., brain neurotransmitters, sex hormones, etc.) and protecting biosystems against poisoning. An enticing property of CYP450s is that entrance of an oxidizable substrate into the active site initiates a series of events that constitute the catalytic cycle, which functions "automatically" in a regulated sequence of events culminating in the production of the oxidized substrates (e.g., hydroxylated, epoxidized, etc.), oftentimes with remarkable stereo- and regioselectivities. It is timely to demonstrate how theory uses molecular dynamics (MD) simulations and quantum-mechanical/molecular-mechanical (QM/MM) calculations to complement experiments and elucidate the choreography by which the protein regulates the catalytic cycle.CYP450 is a heme enzyme that contains a ferric ion (Fe III ) coordinated by a porphyrin ligand, a water molecule, and a cysteinate ligand that is provided by a strategic residue of the encapsulating protein. While many of the individual steps are sufficiently well-understood, we shall provide here an overview of the factors that cause all of the steps to be sequentially coordinated. To this end, we use examples from three different CYP450 enzymes: the bacterial ones CYP450 BM3 and CYP450 CAM and the mammalian enzyme CYP450 3A4 . The treatment is limited to the catalytic cycle, as aspects of two-state reactivity were reviewed previously (e.g., Shaik, S.; et al. Chem. Rev. 2005, 105, 2279).What are the principles that govern the seeming automatic feature? For example, how do substrate entrance and binding gate the enzyme? How does the reductase attachment to the enzyme affect the next steps? What triggers the attachment of the reductase? How does the electron transfer (ET) that converts Fe III to Fe II occur? Is the ET coordinated with the entrance of O 2 into the active site? What is the mechanism of the latter step? Since the entrance of the substrate expels the water molecules from the active site, how do water molecules re-enter to form a proton channel, which is necessary for creating the ultimate oxidant Compound I? How do mutations that disrupt the water channel nevertheless create a competent oxidant? By what means does the enzyme produce regio- and stereoselective oxidation products? What triggers the departure of the oxidized product, and how does the exit occur in a manner that generates the resting state ready for the next cycle? This Account shows that the entrance of the substrate triggers all of the ensuing events. © Copyright 2019 American Chemical Society.

Chemistry

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Accounts of Chemical Research

Cytochrome P450 - The Wonderful Nanomachine Revealed through Dynamic Simulations of the Catalytic Cycle

Physics

Prediction of crystal structure and study of transport and optoelectronic properties of NH2 substituted trans-stilbene derivative: A new promising ambipolar organic semiconductor

A lightweight organic material, trans-4′-dimethylamino-4-nitro-α-cyanostilbene, exhibits notable charge carrier mobility (∼10 -4 cm 2 V -1 s -1 ). The non-centrosymmetric material also displays moderate second harmonic generation activity. This is one of the rarest examples of small organic materials displaying semiconductor characteristics. The charge-transfer pathway as elucidated via high-resolution single-crystal X-ray diffraction data based "energy frameworks" and "experimental charge density" analyses is assessed by measuring the charge carrier mobility using the space charge limited current technique on pure single-crystal diode devices. These advanced structural analyses clearly demonstrate that charge transport in organic crystals is purely governed by its molecular packing, especially the π-π stacking geometry. The balanced ambipolar charge transport behavior makes this highly soluble and thermally stable organic crystal promising for applications in optoelectronic devices. Moreover, this report introduces the crucial role of energy frameworks and charge density analyses for fundamental understanding of the structure-property relationship in organic semiconductors. Copyright © 2019 American Chemical Society.

Crystal Growth and Design

Structure-Property Relationship in an Organic Semiconductor: Insights from Energy Frameworks, Charge Density Analysis, and Diode Devices

Ever since the discovery of two-dimensional (2D) material graphene, there has been huge interest in the exploration of low-dimensional materials that can be exfoliated from their three-dimensional counterpart with enriched properties due to quantum confinement. Two members of the Sn-S family, Pnma-SnS and P3Im1-SnS 2 that possess a layered structure with 2D nanosheets stacked via weak van der Waals (vdW) interactions, have widely been studied in this regard. The other member, Pnma-Sn 2 S 3 , comprising one-dimensional (1D) nanochains bound via vdW interactions, has never been investigated in the view of exfoliated 1D analogue. In this work, we therefore comprehensively studied 1D-Sn 2 X 3 (X = S and Se) nanochains and demonstrated them to be stable and exfoliable from their bulk counterpart. Further, it is also shown that the exfoliated 1D nanochains can easily be identified from their bulk counterpart using Raman, infrared, and X-ray spectroscopies. Our calculations predict a direct band gap of 2.35 eV (1.67 eV) for 1D-Sn 2 S 3 (1D-Sn 2 Se 3 ) nanochains under the Heyd, Scuseria, and Ernzerhof functional, with a broad absorption region lying between 2 and 8 eV, lower reflection, high charge-carrier mobility with ambipolar characteristics, as well as a larger value of the Seebeck coefficient and a smaller value of the thermal conductivity, resulting in a better thermoelectric figure of merit. These interesting electronic, optical, transport, and thermoelectric properties make 1D-Sn 2 X 3 nanochains a potential candidate for the application in future optoelectronic and thermoelectronic devices, in fact, better than three-dimensional (3D)-Sn 2 X 3 for few of the applications. Moreover, 3D-Sn 2 Se 3 is also investigated in detail in this work, which to the best of our knowledge has not been done before. © 2019 American Chemical Society.

ACS Applied Materials and Interfaces

One-Dimensional-Sn 2 X 3 (X = S, Se) as Promising Optoelectronic and Thermoelectronic Materials: A Comparison with Three-Dimensional-Sn 2 X 3

Wildlife habitat corridors are components of landscapes, which facilitate the movement of organisms and processes between areas of intact habitat, and thus provide landscape corridor as well as serve as an ideal component to study and understand physiological ecology. Corridors are thus regions within a given landscape that generally comprise native vegetation, and connect otherwise fragmented, disconnected, non-contiguous wildlife habitat patches in the landscape. The purpose of designing corridors as a conservation strategy is primarily to counter, and to the extent possible, mitigate the impacts of habitat fragmentation and loss on the biodiversity of the landscape, as well as support continuance of land use for essential local and global economic activities in the region of reference. In this paper, we use game theory and graph theory to model and design a wildlife corridor in the Central India – Eastern Ghats landscape complex, with tiger (Panthera tigris tigris) as the focal species. We construct a graph using the habitat patches supporting wild tiger populations in the landscape complex as vertices and the possible paths between these vertices as edges. A cost matrix is constructed to indicate the cost incurred by the tiger for passage between the habitat patches in the landscape (based on Shelford's Law of Tolerance), by modelling a two-person Prisoner's Dilemma game. A minimum spanning tree is then obtained by employing Kruskal's algorithm, which would suggest a feasible tiger corridor network for the tiger population within the landscape complex. Additionally, analysis of the graph is done using various centrality measures, in order to identify and focus on potentially important habitat patches, and their potential community structure. Correlation analysis is performed on the centrality indices to draw out interesting trends in the network. © 2019 Elsevier B.V.

Mathematics

Ecological Informatics

A graph theoretic approach for modelling tiger corridor network in Central India-Eastern Ghats landscape complex, India

Charge transport properties of common donor copolymers in organic photovoltaics, poly({4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl}{3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl}) (PTB7) and poly([2,6′-4,8-di(5-ethylhexylthienyl)benzo[1,2-b;3,3-b]dithiophene]{3-fluoro-2[(2-ethylhexyl) carbonyl]thieno[3,4-b]thiophenediyl}) (PTB7-Th), with molecular structures differing only in the pendant group, are studied. This is the first report of field-effect transistor mobility (µ FET ) of PTB7-Th (0.14 cm 2 V −1 s −1 ) and the highest µ FET for PTB7 (0.01 cm 2 V −1 s −1 ). µ FET of PTB7-Th is found to be almost one order of magnitude higher than PTB7. To understand the influence of molecular structure on charge transport, hole reorganization energy (λ h ) is calculated from first-principles. λ h of PTB7-Th (≈150 meV) is found to be lower than PTB7 (≈346 meV). Further, the ratio of hopping rate versus square of charge transfer integral calculated from Marcus theory using λ h for these systems is found to indicate a higher rate of hole transfer across dimers or homojunction interface for PTB7-Th. These results are supplemented by experimentally determined λ using bulk-heterojunction organic solar cells, where λ PTB7-Th ≈200 meV and λ PTB7 ≈310 meV follow a similar trend. The effective hole-mobility estimation from BHJ devices correlates well with these λ values. This study provides understanding of charge transport properties via reorganization energy, as a function of pendant group without altering the backbone of the chains. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Advanced Functional Materials

Influence of Pendant Group on Mobility of Organic Thin Film Transistor in Correlation with Reorganization Energy of Molecules

We propose a new form of Lagrangian that shows branching for the associated Hamiltonian and has relevance to the quadratic type and mixed linear-quadratic Liénard-type nonlinear dynamical equations on adjusting the underlying parameters. Non-uniqueness of the Lagrangian is pointed out and a particular one when Fourier transform is demonstrated to depict a momentum-dependent quantum-like mass system when expanded binomially. © 2019 World Scientific Publishing Company.

Modern Physics Letters A

Nonstandard Lagrangians and branching: The case of some nonlinear Liénard systems

Ecosystems are constantly under threat by invasive species which alter existing ecological networks as they spread. We use Geographic Information System methods coupled with complex network analysis to model the movement and spread of Lantana camara in Rajaji Tiger Reserve, India, as understanding spatial aspects of the spread mechanism are essential for better resource management in the region. Lantana mapping was carried out by field observations along multiple transects and plots, and the data generated was used as input for maximum entropy modelling to identify land patches in the study area that are favourable for lantana growth. The patch information so obtained was integrated with a raster map generated by identifying different topographical features in the study area which are favourable for lantana growth. The integrated data was analysed with a complex network perspective, where relatively dense and large potential lantana distribution patches were considered as vertices, connected by relatively sparse and thin potential lantana continuities, identified as edges. The network centrality analysis reveal key patches in the study area that play specialized roles in the spread of lantana in a large region. Hubs in the lantana network are primarily identified as dry seasonal river beds. The lantana network is found to exhibit small-world architecture with a well formed community structure. We infer that the above properties of the lantana network are major contributors in regulating the movement and spread of the plant through the entire region of study. © 2019 Elsevier B.V.

Ecological Complexity

A network theoretic study of potential invasion and spread of Lantana camara in a part of Rajaji Tiger Reserve, India

In recent years, covalent organic frameworks (COFs) have attracted considerable attention due to their crystalline and porous nature, which positions them as intriguing candidates for diverse applications such as catalysis, sensing, or optoelectronics. The incorporation of dyes or semiconducting moieties into a rigid two-dimensional COF can offer emergent features such as enhanced light harvesting or charge transport. However, this approach can be challenging when dealing with dye molecules that exhibit a large aromatic backbone, since the steric demand of solubilizing side chains also needs to be integrated into the framework. Here, we report the successful synthesis of DPP2-HHTP-COF consisting of diketopyrrolopyrrole (DPP) diboronic acid and hexahydroxytriphenylene (HHTP) building blocks. The well-known boronate ester coupling motif guides the formation of a planar and rigid backbone and long-range molecular DPP stacks, resulting in a highly crystalline and porous material. DPP2-HHTP-COF exhibits excellent optical properties including strong absorption over the visible spectral range, broad emission into the NIR and a singlet lifetime of over 5 ns attributed to the formation of molecular stacks with J-type interactions between the DPP subcomponents in the COF. Electrical conductivity measurements of crystalline DPP2-HHTP-COF pellets revealed conductivity values of up to 10 -6 S cm -1 .