Department of Chemistry

Indian Institute of Technology Palakkad&nbsp;(IIT Palakkad or IIT PKD) is a public autonomous&nbsp;engineering&nbsp;and&nbsp;research&nbsp;institute located in&nbsp;Palakkad,&nbsp;Kerala. It was&nbsp;one of the five new&nbsp;IITs&nbsp;proposed in the&nbsp;2014 Union budget of India. The campus was inaugurated on 3 August 2015. The institute has 94 faculty, 978 students, and 63 non-teaching staffs.

IT Palakkad currently offers four-year Bachelor of Technology (B.Tech) and two years MS programmes in 8 different engineering disciplines including&nbsp;Computer Science, Electrical, Mechanical, Civil among others.

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IIT Palakkad

In this work, we developed an electrochemical aptasensor by using methylene blue (MB) redox probe labeled aptamer as a signaling fragment and functional graphene oxide (FGO) as the signal-enlarging platform. The role of functionalized graphene oxide was not mere to serve as a covalent immobilization support for aptamer sequences, but its catalytic signal amplification behavior towards methylene blue was demonstrated for the first time in the present work. The functionalized graphene oxide was cast on screen-printed carbon electrodes (SPCE), and then the MB-tagged aptamer was covalently immobilized on SPCE by using hexamethylenediamine (HMDA) as a spacer via carbodiimide amide-bonding chemistry. Aflatoxin B1 (AFB1) analyte molecule detection was accomplished by the aptamer conjugated redox probe, which undergoes/involves a conformational change in the complex structure of aptamer consequent to AFB1 binding. The proposed assay permitted to detect AFB1 in the linear range of 0.05–6.0 ng mL−1 with a very low limit of detection (LOD) (0.05 ng mL−1). The present principle aptasensor was tested to screen the alcoholic beverage samples for AFB1 detection and good recovery values were obtained. © 2017 Elsevier Ltd

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Electrochimica Acta

An electrochemical aptasensor based on functionalized graphene oxide assisted electrocatalytic signal amplification of methylene blue for aflatoxin B1 detection

A V-shaped 4-amino-1,8-naphthalimide derived dipyridyl ligand comprising the Tröger's base structural motif has been synthesised and subsequently used in the formation of two new supramolecular coordination polymers. © 2017 The Royal Society of Chemistry.

Fulltext

Chemical Communications

Supramolecular coordination polymers using a close to 'V-shaped' fluorescent 4-amino-1,8-naphthalimide Tröger's base scaffold

We demonstrate that synthetically controlled concurrent stabilization of Fe and O vacancy defects on the surface of interbraided nanoscale hematite (Fe2-δO3-v) renders an interesting surface chemistry which can reduce CO2 to CO at room temperature (RT). Importantly, we realized a highly enhanced output of 410 μmol h-1 g-1 at RT, as compared to that of 10 μmol h-1 g-1 for bulk hematite. It is argued based on the activity degradation under cycling and first principles density functional theory calculations that the excess chemical energy embedded in the defect-stabilized surface is expended in this high-energy conversion process, which leads to progressive filling up of oxygen vacancies. © 2017 American Chemical Society.

ACS Omega

Room-Temperature Activation of CO2 by Dual Defect-Stabilized Nanoscale Hematite (Fe2-δO3-v): Concurrent Role of Fe and O Vacancies

A V-Shaped 4-amino-1,8-napthalimide derived tetracarboxylic acid linker (L; bis-[N-(1,3-benzenedicarboxylic acid)]-9,18-methano-1,8-naphthalimide-[b,f][1,5]diazocine) comprising the Tröger's base (TB) structural motif was rationally designed and synthesised to access a nitrogen-rich fluorescent supramolecular coordination polymer. By adopting the straight forward precipitation method, a new luminescent nanoscale Zn(ii) coordination polymer (TB-Zn-CP) was synthesized in quantitative yield using Zn(OAc)2·2H2O and tetraacid linker L (1 : 0.5) in DMF at room temperature. The phase-purity of as-synthesised TB-Zn-CP was confirmed by X-ray powder diffraction analysis, infra-red spectroscopy, and elemental analysis. Thermogravimetric analysis suggests that TB-Zn-CP is thermally stable up to 330 °C and the morphological features of TB-Zn-CP was analysed by SEM and AFM techniques. The N2 adsorption isotherm of thermally activated TB-Zn-CP at 77 K revealed a type-II reversible adsorption isotherm and the calculated Brunauer-Emmett-Teller (BET) surface area was found to be 72 m2 g−1. Furthermore, TB-Zn-CP displayed an excellent CO2 uptake capacity of 76 mg g−1 at 273 K and good adsorption selectivity for CO2 over N2 and H2. The aqueous suspension of as-synthesized TB-Zn-CP showed strong green fluorescence (λmax = 520 nm) characteristics due to the internal-charge transfer (ICT) transition and was used as a fluorescent sensor for the discriminative sensing of nitroaromatic explosives. The aqueous suspension of TB-Zn-CP showed the largest quenching responses with high selectivity for phenolic-nitroaromatics (4-NP, 2,4-DNP and PA) even in the concurrent presence of other potentially competing nitroaromatic analytes. The fluorescence titration studies also provide evidence that TB-Zn-CP detects picric acid as low as the parts per billion (26.3 ppb) range. Furthermore, the observed fluorescence quenching responses of TB-Zn-CP towards picric acid were highly reversible. The highly selective fluorescence quenching responses including the reversible detection efficiency make the nanoscale coordination polymer TB-Zn-CP a potential material for the discriminative fluorescent sensing of nitroaromatic explosives. © The Royal Society of Chemistry.

Chemical Science

A supramolecular Tröger's base derived coordination zinc polymer for fluorescent sensing of phenolic-nitroaromatic explosives in water

An efficient electrochemical sensor for selective detection of the neurotransmitter, epinephrine (Epn), has been fabricated with the aid of a functionalized multiwall carbon nanotube–chitosan biopolymer nanocomposite (Chit-fCNT) electrode. Multiwall carbon nanotubes (CNT) were successfully functionalized with the aid of nitric acid and confirmed by the Raman spectral data. Functionalized carbon nanotubes (fCNT) were dispersed in chitosan solution and the resulting bio-nanocomposite was used for the fabrication of sensor surface by drop and cast method. Electrochemical characteristics of the fabricated sensor were understood using cyclic, differential pulse voltammetry (CV, DPV) and electrochemical impedance analysis for the detection of Epn in phosphate buffer (pH 7.4). CV and impedance analysis revealed that the Chit-fCNT modified electrode enhances the electrodic reaction of Epn and facilitated the electron transfer more readily compared to that of bare electrode. Applying DPV for the detection of Epn, achieved 30 nM as the lowest detection limit in the determination range of 0.05–10 μM and the analytical time as low as 10 s. Selective determination of Epn against the coexistence of a number of biological electroactive interferents and reproducible results for the determination of Epn were demonstrated. The present biosensor has been found efficient for successful direct determination of Epn from pharmaceutical adrenaline formulations and urine samples. © 2017 Elsevier B.V.

Materials Science and Engineering C

Carbon nanotube ensembled hybrid nanocomposite electrode for direct electrochemical detection of epinephrine in pharmaceutical tablets and urine

A Tröger's base-functionalised covalent organic polymer (TB-COP) was synthesised and used as an adsorbent for the efficient removal of picric acid (PA) from water through the use of weak and reversible supramolecular interactions such as hydrogen bonding and π-π interactions. TB-COP was readily synthesised in quantitative yield using a one-pot metal-free polymerisation reaction strategy between a semi-flexible aromatic triamine [L; benzene-1,3-5-tricarboxylic acid-tris-(4-amino-phenyl-amide)] and dimethoxymethane. The molecular structure, physicochemical and morphological characteristics of TB-COP were analysed by using various spectroscopic and imaging techniques. Thermogravimetric analysis showed TB-COP to be thermally stable up to 380 °C; while the calculated Brunauer-Emmett-Teller (BET) surface area was found to be 34 m2 g-1 at 273 K. The picric acid adsorption study of the activated TB-COP showed an excellent adsorption capacity of ca. 90% within 60 minutes of contact time at 298 K (Langmuir isotherm model: KL = 0.0541 ± 6 L mg-1, R2 = 0.9962); the adsorption efficiency being shown to improve with increasing temperature. The extraction of PA was also clearly visible to the naked eye, where the yellow colored PA solution became transparent upon addition of TB-COP. Other interfering phenolic organic pollutants showed poor to moderate adsorption efficiency. Importantly, TB-COP could be used to store PA over a long period of time in a safe manner, without any leakage or any significant loss in extraction efficiency. Moreover, the polymer could be reused for several adsorption cycles, as PA could be released back into the solution by simply changing the pH of the aqueous media. This makes TB-COP an extremely promising material for the selective and efficient removal of picric acid from water, and TB-COP can be considered as being a 'fast' and naked eye colorimetric indicator for such analytes. © 2017 The Royal Society of Chemistry.

Journal of Materials Chemistry A

Reversible adsorption and storage of secondary explosives from water using a Tröger's base-functionalised polymer

Encapsulation of dye molecules is used as a means to achieve charge separation across different dielectric environments. We analyze the absorption and emission spectra of several coumarin molecules that are encapsulated within an octa-acid dimer forming a molecular capsule. The water-solvated capsule effect on the coumarin's electronic structure and absorption spectra can be understood as due to an effective dielectric constant where the capsule partially shields electrostatically the dielectric solvent environment. Blue-shifted emission spectra are explained as resulting from a partial intermolecular charge transfer where the capsule is the acceptor, and which reduces the coumarin relaxation in the excited state. © 2017 American Chemical Society.

Journal of Physical Chemistry C

What is the Optoelectronic Effect of the Capsule on the Guest Molecule in Aqueous Host/Guest Complexes? A Combined Computational and Spectroscopic Perspective

A reusable electrochemical sensor ensembling carbon nanotubes and a conducting polymer together is fabricated for the detection of an important anti-cancer drug, dacarbazine (DTIC). A thin film of a conducting polymer, poly(2-amino-1,3,4-thiadiazole) (poly-ATD), is formed on the carbon nanotube paste electrode (CNPE) by employing a potentiodynamic polymerization technique. The fabricated sensor surface has been characterized by FTIR spectroscopy and scanning electron microscopy (SEM) for the structural and chemical properties of the electrode system. The electrochemical capability of the fabricated poly-ATD/CNPE composite electrode for the detection of DTIC is examined by cyclic voltammetry (CV) and electrochemical impedance spectroscopic analysis (EIS), and the poly-ATD/CNPE electrode is found to be efficient for electrocatalytic oxidation of DTIC. Optimization and evaluation of the sensor system are examined by differential pulse voltammetry (DPV). A linear relationship of DTIC concentration over the peak current of DPVs is exhibited over a wide concentration range of 0.05–24.0 μM with a low detection limit (3σ/b) of 35 nM. Steady state current–time analysis experiments under hydrodynamic conditions exhibited a low detection limit of 20 nM, and the analysis time is as low as 10 s. Practical utility of the fabricated poly-ATD/CNPE biosensor for the detection of DTIC directly from artificial urine and pharmaceutical formulations has been demonstrated with very good recovery limits. [Figure not available: see fulltext.] © 2017, Springer Science+Business Media New York.

Electrocatalysis

Conducting Polymer-Layered Carbon Nanotube as Sensor Interface for Electrochemical Detection of Dacarbazine In-Vitro

Mammalian SIRT7 is a member of the sirtuin family that regulates multiple biological processes including genome stability, metabolic pathways, stress responses, and tumorigenesis. SIRT7 has been shown to be important for ribosome biogenesis and transcriptional regulation. SIRT7 knockout mice exhibit complications associated with fatty liver and increased aging in hematopoietic stem cells. However, the molecular basis for its biological function remains unclear, in part due to the lack of efficient enzymatic activity in vitro. Previously, we have demonstrated that double-stranded DNA could activate SIRT7's deacetylase activity in vitro, allowing it to deacetylate H3K18 in the context of chromatin. Here, we show that RNA can increase the catalytic efficiency of SIRT7 even better and that SIRT7 can remove long chain fatty acyl groups more efficiently than removing acetyl groups. Truncation and mutagenesis studies revealed residues at both the amino and carboxyl termini of SIRT7 that are involved in RNA-binding and important for activity. RNA immunoprecipitation-sequencing (RIP-seq) identified ribosomal RNA (rRNA) as the predominant RNA binding partner of SIRT7. The associated RNA was able to effectively activate the deacetylase and defatty-acylase activities of SIRT7. Knockdown of SIRT7 increased the lysine fatty acylation of several nuclear proteins based on metabolic labeling with an alkyne-tagged fatty acid analog, supporting that the defatty-acylase activity of SIRT7 is physiologically relevant. These findings provide important insights into the biological functions of SIRT7, as well as an improved platform to develop SIRT7 modulators. © 2016 American Chemical Society.

ACS Chemical Biology

SIRT7 is an RNA-activated protein lysine deacylase

Prion-like misfolding of superoxide dismutase 1 (SOD1) is associated with the disease ALS, but the mechanism of misfolding remains unclear, partly because misfolding is difficult to observe directly. Here we study the most misfolding-prone form of SOD1, reduced un-metallated monomers, using optical tweezers to measure unfolding and refolding of single molecules. We find that the folding is more complex than suspected, resolving numerous previously undetected intermediate states consistent with the formation of individual β-strands in the native structure. We identify a stable core of the protein that unfolds last and refolds first, and directly observe several distinct misfolded states that branch off from the native folding pathways at specific points after the formation of the stable core. Partially folded intermediates thus play a crucial role mediating between native and non-native folding. These results suggest an explanation for SOD1's propensity for prion-like misfolding and point to possible targets for therapeutic intervention. © 2017 The Author(s).