Department of Chemistry

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IIT Jodhpur

Small-molecule inhibition of the interaction between the KRas oncoprotein and the chaperone PDE6δ impairs KRas spatial organization and signaling in cells. However, despite potent binding in vitro (KD&lt;10 nm), interference with Ras signaling and growth inhibition require 5–20 μm compound concentrations. We demonstrate that these findings can be explained by fast release of high-affinity inhibitors from PDE6δ by the release factor Arl2. This limitation is overcome by novel highly selective inhibitors that bind to PDE6δ with up to 7 hydrogen bonds, resulting in picomolar affinity. Their release by Arl2 is greatly decreased, and representative compounds selectively inhibit growth of KRas mutated and -dependent cells with the highest activity recorded yet. Our findings indicate that very potent inhibitors of the KRas-PDE6δ interaction may impair the growth of tumors driven by oncogenic KRas. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

World University root node

Angewandte Chemie - International Edition

A PDE6δ-KRas Inhibitor Chemotype with up to Seven H-Bonds and Picomolar Affinity that Prevents Efficient Inhibitor Release by Arl2

Guided by the principle of biology-oriented synthesis, a collection of compounds with decahydro-4,8-epoxyazulene scaffold occurring in bioactive natural products was synthesized by the rhodium(II)-catalyzed 1,3-dipolar cycloaddition reaction of pentafulvenes and carbonyl ylides. The products can be obtained in moderate to high yields, with moderate enantioselectivity and excellent diastereoselectivity and regioselectivity. © Georg Thieme Verlag Stuttgart. New York.

Synlett

Biology-Oriented Synthesis of Decahydro-4,8-epoxyazulene Scaffolds

LiMn2 – xGdxO4 (x = 0.00, 0.01 and x = 0.04) spinel active material were prepared by sol-gel method. The morphology, crystal structure, thermal stability and electrochemical properties of the synthesized samples were evaluated. Gd-doping maintains the cubic spinel structure of LiMn2O4, leads to a decrease of the average particle size, and has a strong influence on the electrochemical properties of the cathodes. LiMn2 – xGdxO4 cathode materials show two pairs of separated redox peaks, independently of the Gd-doping. After 40 charge-discharge cycles at C/2, the discharge capacity was 55.9 mAh·g− 1 and 33 mAh·g− 1 for x = 0.04 and x = 0, respectively, corresponding to a capacity retention of 80% and 70%, respectively. The Gd-doped with x = 0.04 showed improved cycling performance with respect to pristine LiMn2O4 due the smaller particle size and superior structural stability, showing its suitability for lithium-ion battery applications. © 2016 Elsevier B.V.

Solid State Ionics

Synthesis and improved electrochemical performance of LiMn2 – xGdxO4 based cathodes

Dendritic nanostructures of fluorinated α-Fe2O3 are synthesized using Potassium Ferrocyanide along with Selectfluor™ (F-TEDA), HF, TBABF4, NaF and NH4F as Fe and F precursors respectively in an in-situ hydrothermal process. The choice of sources is based on the nature of fluorine; F-TEDA uniquely acts as a source for electrophilic fluorine while others are nucleophilic in nature. The effect of fluorination on α-Fe2O3 nanostructures is examined from the interplay between (110) and (104) growth direction and crystallite size by X-Ray diffraction analysis and the amount of fluorination is observed by elemental analysis. A significant change in the magnetic property of α-Fe2O3 is observed for different concentrations of F-TEDA. Pristine α-Fe2O3 undergoes an antiferromagnetic to ferromagnetic transition with saturation magnetization value of ~ 13 emu/g and coercivity of 109.8 Oe. However, α-Fe2O3 nanostructures prepared with HF, NH4F, TBABF4 and NaF in absence of fluorination remain antiferromagnetic despite of changes in preferred orientation and crystallite size. The interesting magnetic properties arising from F-TEDA is attributed to surface fluorination that results in uncompensated surface spins. © 2017 Elsevier Ltd

Materials and Design

Electrophilic fluorination of α-Fe2O3 nanostructures and influence on magnetic properties

3-Oxetanone is a strained cyclic molecule which plays an important role in synthetic chemistry. A few studies exist in the literature about the equilibrium properties of this molecule and the dissociation patterns of substituted 3-oxetanones. For the unsubstituted 3-oxetanone, formation of ketene (CH2CO) and formaldehyde (HCHO) was considered to be the major dissociation pathway. In a recent work, pyrolysis products of 3-oxetanone molecule in the gas phase were investigated by Fourier transform infrared spectroscopy and photoionization mass spectrometry. In this study, an additional dissociation channel forming ethylene oxide (c-C2H4O) and carbon monoxide CO was reported. In the present work, gas phase dissociation chemistry of 3-oxetanone was investigated by electronic structure theory, ab initio classical chemical dynamics simulations, and Rice-Ramsperger-Kassel-Marcus (RRKM) rate constant calculations. The barrier height for the ethylene oxide channel was found to be much higher than the ketene pathway. The dynamics simulations were performed at three different total energies, viz., 150, 200, and 300 kcal/mol, and multiple reaction pathways and varying branching ratios observed. A new dissociation channel involving a ring-opened isomer of ethylene oxide was identified in the simulations. This pathway has a lower energy barrier and was dominant in our dynamics simulations. © 2017 American Chemical Society.

Journal of Physical Chemistry A

Dissociation Chemistry of 3-Oxetanone in the Gas Phase

This paper describes the framework for event triggered control of a plant possessing two time scales. The periodic sampling requirement is relaxed and states are sampled based on a triggering rule. The dynamic trigger function where event triggering threshold varies with time has been used. Triggering function parameters are different for slow and fast states and events are detected independently in the two subsystems. This also allows the sensors for slow and fast states to be geographically distributed in the network. Further singular perturbation technique is used to decouple the system into fast and slow subsystems and stability of the overall system is investigated. It is proved that the closed loop system asymptotically converges to an adjustable region around the equilibrium point and a minimum bound on inter-execution time is also guaranteed. Asymptotic stability may also be obtained if the parameters of trigger function are adequately selected. Simulation results manifest the efficacy of the proposed approach and verify the theoretical analysis. © 2017 IEEE.

Department of Electrical Engineering

2017 Indian Control Conference, ICC 2017 - Proceedings

Event triggered control of two time scale system

Ideally, transparent heaters exhibit uniform temperature, fast response time, high achievable temperatures, low operating voltage, stability across a range of temperatures, and high optical transmittance. For metal network heaters, unlike for uniform thin-film heaters, all of these parameters are directly or indirectly related to the network geometry. In the past, at equilibrium, the temperature distributions within metal networks have primarily been studied using either a physical temperature probe or direct infrared (IR) thermography, but there are limits to the spatial resolution of these cameras and probes, and thus, only average regional temperatures have typically been measured. However, knowledge of local temperatures within the network with a very high spatial resolution is required for ensuring a safe and stable operation. Here, we examine the thermal properties of random metal network thin-film heaters fabricated from crack templates using high-resolution IR microscopy. Importantly, the heaters achieve predominantly uniform temperatures throughout the substrate despite the random crack network structure (e.g., unequal sized polygons created by metal wires), but the temperatures of the wires in the network are observed to be significantly higher than the substrate because of the significant thermal contact resistance at the interface between the metal and the substrate. Last, the electrical breakdown mechanisms within the network are examined through transient IR imaging. In addition to experimental measurements of temperatures, an analytical model of the thermal properties of the network is developed in terms of geometrical parameters and material properties, providing insights into key design rules for such transparent heaters. Beyond this work, the methods and the understanding developed here extend to other network-based heaters and conducting films, including those that are not transparent. © 2017 American Chemical Society.

ACS Applied Materials and Interfaces

Microscopic Evaluation of Electrical and Thermal Conduction in Random Metal Wire Networks

Covalent labeling of amino acids in proteins by reactive small molecules, in particular at cysteine SH and lysine NH groups, is a powerful approach to identify and characterize proteins and their functions. However, for the less-reactive carboxylic acids present in Asp and Glu, hardly any methodology is available. Employing the lipoprotein binding chaperone PDE6δ as an example, we demonstrate that incorporation of isoxazolium salts that resemble the structure and reactivity of Woodward's reagent K into protein ligands provides a novel method for selective covalent targeting of binding site carboxylic acids in whole proteomes. Covalent adduct formation occurs via rapid formation of enol esters and the covalent bond is stable even in the presence of strong nucleophiles. This new method promises to open up hitherto unexplored opportunities for chemical biology research. © 2017 Elsevier Ltd

Fulltext

Cell Chemical Biology

Covalent Protein Labeling at Glutamic Acids

A biology-oriented synthesis of 3,3-spiro(2-tetrahydrofuranyl)oxindole derivatives is realized through the rhodium(II)-catalyzed three-component reaction of diazoamides, aldehydes and β-nitrostyrenes. The reactions are conducted under mild conditions and the products are obtained in moderate to good yields with excellent regio- and diastereoselectivity. © 2017 Georg Thieme Verlag Stuttgart, New York.

Synthesis (Germany)

Biology-Oriented Synthesis of 3,3-Spiro(2-tetrahydrofuranyl)oxindoles

The current study involves a simple hydrazine based colorimetric chemo-sensor for selective determination of various anions. The anion-binding ability of the ligand with various anions via polar-non polar interactions and hydrogen bonding has been examined. The sensor displayed significant UV-vis enhancement response to anions such as fluoride, acetate, hydroxide, cyanide and hydrogen sulphate, with respect to concentration and time. The rate constants (K) and binding constants, Ka, for these anions have been measured by using Benesi-Hildebrand equation. A time dependent NMR study revealed stronger interaction for cyanide and fluoride ions among competing anions. © 2017 by Elsevier B.V.