Department of Chemistry

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Understanding the regulatory factors of self-assembly processes is a necessity in order to modulate the nano-structures and their properties. Here, the self-assembly mechanism of a peptide-perylenediimide (P-1) conjugate in mixed solvent systems of THF/water is studied and the semiconducting properties are correlated with the morphology. In THF, right handed helical fibers are formed while in 10% THF-water, the morphology changes to nano-rings along with a switch in the helicity to left-handed orientation. Experimental results combined with DFT calculations reveal the critical role of thermodynamic and kinetic factors to control these differential self-assembly processes. In THF, P-1 forms right handed helical fibers in a kinetically controlled fashion. In case of 10% THF-water, the initial nucleation of the aggregate is controlled kinetically. Due to differential solubility of the molecule in these two solvents, elongation of the nuclei into fibers is restricted after a critical length leading to the formation of nano-rings which is governed by the thermodynamics. The helical fibers show superior semi-conducting property to the nano-rings as confirmed by conducting-AFM and conventional I-V characteristics. © 2017 The Author(s).

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Fulltext

Scientific Reports

Solvent Assisted Tuning of Morphology of a Peptide-Perylenediimide Conjugate: Helical Fibers to Nano-Rings and their Differential Semiconductivity

The K-Ras GTPase is a major target in anticancer drug discovery. However, direct interference with signaling by K-Ras has not led to clinically useful drugs yet. Correct localization and signaling by farnesylated K-Ras is regulated by the prenyl binding protein PDEδ. Interfering with binding of PDEδ to K-Ras by means of small molecules provides a novel opportunity to suppress oncogenic signaling. Here we describe the identification and structure-guided development of novel K-Ras–PDEδ inhibitor chemotypes based on pyrrolopyridazinones and pyrazolopyridazinones that bind to the farnesyl binding pocket of PDEδ with low nanomolar affinity. We delineate the structure–property relationship and in vivo pharmacokinetic (PK) and toxicokinetic (Tox) studies for pyrazolopyridazinone-based K-Ras–PDEδ inhibitors. These findings may inspire novel drug discovery efforts aimed at the development of drugs targeting oncogenic Ras. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Chemistry - A European Journal

Development of Pyridazinone Chemotypes Targeting the PDEδ Prenyl Binding Site

Programmed cell death-1 (PD-1) is a coinhibitory receptor that suppresses T cell activation and is an important cancer immunotherapy target. Upon activation by its ligand PD-L1, PD-1 is thought to suppress signaling through the T cell receptor (TCR). By titrating PD-1 signaling in a biochemical reconstitution system, we demonstrate that the coreceptor CD28 is strongly preferred over the TCR as a target for dephosphorylation by PD-1-recruited Shp2 phosphatase. We also show that CD28, but not the TCR, is preferentially dephosphorylated in response to PD-1 activation by PD-L1 in an intact cell system. These results reveal that PD-1 suppresses T cell function primarily by inactivating CD28 signaling, suggesting that costimulatory pathways play key roles in regulating effector T cell function and responses to anti-PD-L1/PD-1 therapy.

Science

T cell costimulatory receptor CD28 is a primary target for PD-1-mediated inhibition

An asymmetric domino Michael-hydroalkoxylation reaction of trans-α-alkynyl-nitroolefins with N-arylpyrazolinones has been accomplished using a chiral bifunctional squaramide catalyst. Under the organocatalytic method, a broad range of tetrahydropyrano[2,3-c]pyrazoles with an exocyclic alkene at the C-6 position were prepared in high yields and excellent stereoselectivities. The presence of an exocyclic double bond and nitro group in the pyranopyrazoles provide a wide scope for further structural transformations. © 2017 Elsevier Ltd

Tetrahedron Letters

Enantioselective access to tetrahydropyrano[2,3-c]pyrazoles via an organocatalytic domino Michael-hydroalkoxylation reaction

In this paper, we consider the event triggered control of the singularly perturbed linear system, where the communication between sensor and the controller/actuator is through a digital communication network and the transmission is based on some state dependent criterion. The models of slow and fast subsystems of the plant are added at the controller and are used for the estimation of states between the transmission times. Whenever the difference between estimated and actual states exceeds a certain threshold, controller is updated with the actual states of the plant provided by the sensor. This effectively reduces the communication frequency. The stability properties of overall closed loop system is studied and it is found that for sufficiently small value of singular perturbation parameter, system attains practical stability and by adequately selecting trigger function parameters, asymptotic stability is also achieved. A numerical example is shown to illustrate the results of the paper. © 2017 IEEE.

Department of Electrical Engineering

Proceedings of the IEEE International Conference on Industrial Technology

Event triggered control of singularly perturbec linear system based on its slow and fast model

Abstract: Formation of simple organic species such as glycine in the interstellar medium and transportation to earth via meteorites is considered to be a possible route for ‘Origin of Life’ on earth. Glycine formation has been proposed to occur via two different pathways involving formaldehyde (HCHO) and methanimine (CH 2= NH) as key intermediates. In the second pathway, which is the topic of this paper, CH 2= NH reacts with CO and H 2O forming neutral glycine. In a recent article (Nhlabatsi et al. in Phys. Chem. Chem. Phys. 18:375, 2016), detailed electronic structure calculations were reported for the reaction between CH 2= NH , CO and (H2O)n, n= 1 , 2 , 3 , and 4, forming glycine in the interstellar media. The presence of additional water molecule(s) for this reaction reduces reaction barrier - thus exhibiting a catalytic effect. This effect was described in terms of efficient proton transfer mediated by the additional water molecule through a relay transport mechanism. In the present article, we report ab initio classical trajectory simulations for the interstellar formation of glycine for the above mentioned reaction with n= 1 and 2. The trajectories were generated on-the-fly over a density functional B3LYP/6-31++G(3df,2pd) potential energy surface. Our simulations indicate that the above proposed catalytic effect by the additional water molecule(s) may not be a classical effect. Graphical Abstract: Synopsis: Glycine formation in the interstellar media via the CH 2= NH + CO + H 2O reaction was investigated by classical chemical dynamics simulations. This reaction has a large barrier which reduces in presence of additional water molecules. Our simulations indicate that the proposed catalytic effect by the additional water molecules may not be a classical effect. [Figure not available: see fulltext.]. © 2017, Indian Academy of Sciences.

Journal of Chemical Sciences

Classical dynamics simulations of interstellar glycine formation via CH 2= NH + CO + H 2O reaction

Gas phase decomposition of protonated amino acids are of great interest due to their role in understanding protein and peptide chemistry. Several experimental and theoretical studies have been reported in the literature on this subject. In the present work, decomposition of the aromatic amino acid protonated tryptophan was studied by on-the-fly classical chemical dynamics simulations using density functional theory. Mass spectrometry and electronic structure theory studies have shown multiple dissociation pathways for this biologically relevant molecule. Unlike aliphatic amino acids, protonated tryptophan dissociates via NH3 elimination rather than the usual iminium ion formation by combined removal of H2O and CO molecules. Also, a major fragmentation pathway in the present work involves Cα-Cβ bond fission. Results of the chemical dynamics simulations reported here are in overall agreement with experiments, and detailed atomic level mechanisms are presented. © 2017 American Chemical Society.

Journal of Physical Chemistry A

Classical Dynamics Simulations of Dissociation of Protonated Tryptophan in the Gas Phase

The present study highlights platinum nanoparticles incorporated chiral polyamide for asymmetric hydrogenation of carbonyl group. Chiral polyamides are synthesized from chiral monomers, camphoric dichloride and achiral diamine monomers by interfacial condensation reaction. This chiral polyamide supports have helical structure with molecular chirality. The polyamide helices provide chiral environment to platinum nanoparticles that transfer to substrate during catalytic hydrogenation. The chemical and optical selectivity increases with dispersion of platinum nanoparticles on chiral polyamide which act like isolated single atomic catalytic centers. The distribution of nanoparticles depends on spacer used in amine monomer unit. The catalytically active single atom nanoparticles have preferentially Pt (111) planes and exhibit excellent selectivity up to 10 cycles (TOF &gt; 5400 h−1 and &gt; 99.9% ee) in asymmetric hydrogenation reaction of ethyl 2-oxo-4-phenylbutanoate under solvent free condition. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

ChemistrySelect

Platinum functionalized Chiral Polyamides: Efficient Heterogeneous Catalyst for Solvent Free Asymmetric Hydrogenation of Ethyl 2-oxo-4-phenylbutanoate

A series of dysprosium (Dy) doped LiMn2O4 based spinel cathode materials, LiMn2 − xDyxO4 (x = 0, 0.01, 0.02, 0.03, 0.04, 0.05) for Li ion rechargeable battery application were synthesized by sol-gel process. The physical properties were explored through X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray diffraction (EDX), field emission scanning electron microscopy (FE-SEM), and micro-Raman spectroscopy. Swagelok cell configurations were used for electrochemical characterizations e.g. cyclic voltammetry, rate performance, cycleability and AC impedance. The doping amount of dysprosium has improved the surface morphology (particle size &lt; 1 μm) by reducing particle size. The Dy(0.02) showed improved capacity of 122, 72 and 78 mAh g− 1 at C/10, C/5 and C/10 (recv.) respectively. The lower impedance of Dy(0.02) in comparison of pristine and other derivatives of synthesized cathode materials also supports these outcome. © 2017

Journal of Electroanalytical Chemistry

On the key role of Dy3 + in spinel LiMn2O4 cathodes for Li-ion rechargeable batteries

Emeraldine Hydrochloride salt is coated on copper substrate and studied for hydrogen storage and hydrogen evolution reaction in 1 M NaOH. Phenomenological thermodynamic approach demonstrated elsewhere in conjunction with the cyclic voltammetry data is employed to calculate the solvent modified work function for polyaniline coated copper in alkaline medium as −0.65 eV. The solvated work function is in satisfactory agreement with the band gap difference of π−π* transition in emeraldine base and π- polaron transition in emeraldine salt ca −0.6 eV as reported in the literature. 13C and 1H NMR studies revealed that polyaniline undergoes switching between emeraldine salt and emeraldine base, before and after hydrogen evolution respectively. The volume of hydrogen evolved on polyaniline coated copper is 1.64 times than that on copper as demonstrated by Gas chromatography. Thus emeraldine salt, when stored in NaOH act as hydrogen storage medium and upon electrochemical perturbation can release hydrogen at controlled rate depending on the scan rate employed. © 2017 Hydrogen Energy Publications LLC