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Ramesh Deka

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Papers by Ramesh Deka

Glycome Profiling and Bioprospecting Potential of the Himalayan Buddhist Handmade Paper of Tawang Region of Arunachal Pradesh

Frontiers in Plant Science

The paper and pulp industry (PPI) is one of the largest industries that contribute to the growing... more The paper and pulp industry (PPI) is one of the largest industries that contribute to the growing economy of the world. While wood remains the primary raw material of the PPIs, the demand for paper has also grown alongside the expanding global population, leading to deforestation and ecological imbalance. Wood-based paper production is associated with enormous utilization of water resources and the release of different wastes and untreated sludge that degrades the quality of the environment and makes it unsafe for living creatures. In line with this, the indigenous handmade paper making from the bark of Daphne papyracea, Wall. ex G. Don by the Monpa tribe of Arunachal Pradesh, India is considered as a potential alternative to non-wood fiber. This study discusses the species distribution modeling of D. papyracea, community-based production of the paper, and glycome profiling of the paper by plant cell wall glycan-directed monoclonal antibodies. The algorithms used for ecological and ...

Physical Properties, UV Stability, Biodegradability, and DFT Study of Chicken Feather Fiber Based Composites Crosslinked with Rosin Derivative

Composites due to its advantageous properties for different construction purposes and outdoor app... more Composites due to its advantageous properties for different construction purposes and outdoor applications have gained significant popularity in recent years. Biocomposites had gained importance, mainly due to their eco-friendly and processibility profile. Chicken Feather Fiber (CFF) composite based on modified epoxidized soybean oil (ESO) and natural crosslinker was prepared via compression molding technique. Methacrylic anhydride epoxidized soybean oil (MAESO) as resin, chicken feather fiber flour as a reinforcing agent, and rosin derivative as crosslinker was used to develop the final bio-composite. The fiber/resin ratio was maintained at 30:70 and the percentage of rosin derivative was varied from 0–40 (wt%). The resulting bio-composites were characterized by Fourier transformed infrared (FT-IR) spectroscopy also supported by Density Functional Theory (DFT) calculations. Thermogravimetric analysis (TGA) was done to observe the thermal stability of the bio-composites. Scanning El...

Theoretical insight of OH-initiated mechanistic pathways and kinetics of n-butyl nitrate (CH3CH2CH2CH2ONO2) at 298 K and 1 atm

Tezpur University Tezpur, Napaam-784 028, Assam, India <em>E</em>-<em>mail</... more Tezpur University Tezpur, Napaam-784 028, Assam, India <em>E</em>-<em>mail</em> : ramesh@tezu.ernet.in, nkgour1@tezu.ernet.in Department of Chemistry, Indian Institute of Technology, Guwahati-781 039, Assam, India Department of Physics, Girijananda Chowdhury Institute of Management and Technology, Guwahati-781 017, Assam, India <em>Manuscript received 06 December 2017, accepted 20 December 2017</em> <strong>A detailed density functional studies of the reaction of n-butyl nitrate initiated by OH radical as well as</strong> <strong>atmospheric life-time of the titled molecule have been carried out by using hybrid functional M06-2X </strong> <strong>method along with 6-311+G(d,p) basis set. We obtain the possible H-abstraction channels of the reaction of </strong> <strong>n-butyl nitrate with OH radical on the potential energy surface along with the thermochemistry associated </strong> <strong>wit...

Potential immune epitope map for structural proteins of SARS-CoV-2

Researchers around the world are developing more than 145 vaccines (DNA/mRNA/whole-virus/viral-ve... more Researchers around the world are developing more than 145 vaccines (DNA/mRNA/whole-virus/viral-vector/protein-based/repurposed vaccine) against the SARS-CoV-2 and 21 vaccines are in human trials. However, a limited information is available about which SARS-CoV-2 proteins are recognized by human B- and T-cell immune responses. Using a comprehensive computational prediction algorithm and stringent selection criteria, we have predicted and identified potent B- and T-cell epitopes in the structural proteins of SARS-CoV and SARS-CoV-2. The amino acid residues spanning the predicted linear B-cell epitope in the RBD of S protein (370-NSASFSTFKCYGVSPTKLNDLCFTNV-395) have recently been identified for interaction with the CR3022, a previously described neutralizing antibody known to neutralize SARS-CoV-2 through binding to the RBD of the S protein. Intriguingly, most of the amino acid residues spanning the predicted B-cell epitope (aa 331-NITNLCPFGEVFNATRFASVYAWNRK-356, 403-RGDEVRQIAPGQTGKIAD...

Tuning the transition barrier of H2 dissociation in the hydrogenation of CO2 to formic acid on Ti-doped Sn2O4 clusters

Physical Chemistry Chemical Physics, 2021

Schematic representation of Ti-doping on a pure Sn2O4 cluster for the hydrogenation of CO2 to HCO... more

Decomposition and kinetics of CH2(OH)C(O•)(CH3)CH2Cl radical in the atmosphere: A quantum mechanical study

The quantum mechanical calculations of the decomposition pathways of 1, 2-hydroxy alkoxy radical ... more The quantum mechanical calculations of the decomposition pathways of 1, 2-hydroxy alkoxy radical i.e., CH2(OH)C(O)(CH3)CH2Cl radical have been performed. This radical species has been formed from the successive reactions with O2 molecule and NOx or HO2 radicals with the most stable primary oxidation product of 3-chloro-2-methyl-1propene and OH radical reaction. Geometry optimization and frequency calculations of all the stable species including transition states in the three possible C-C bond scission pathways (i.e., C-CH3, C-CH2Cl and C-CH2OH) of CH2(OH)C(O)(CH3)CH2Cl radical have been performed at M06-2X/6-31+G(d,p) level of theory. Single point energy calculations of all the optimized species at the higher level of CCSD(T) method along with cc-pVTZ triple-zeta basis set have been performed. The rate constants for the various decomposition reactions have been evaluated using Canonical Transition State Theory (CTST) within the temperature range of 250–400 K. Rate constants for C–C ...

Antimycobacterial activity of linoleic acid and oleic acid obtained from the hexane extract of the seeds of Mesua ferrea L. and their in silico investigation

Indian Journal of Natural Products and Resources, 2018

Tuberculosis is responsible for about 8 million deaths worldwide annually. The emergence of multi... more Tuberculosis is responsible for about 8 million deaths worldwide annually. The emergence of multidrug-resistant and extensively drug-resistant strains urgently requires the development of new drugs against tuberculosis. Drug discovery from plants against tuberculosis is an exciting area for exploration. In the present study, the fatty acids- linoleic and oleic acids isolated and identified from the seeds of the plant Mesua ferrea L. exhibited antimycobacterial activity. The analysis was done using Gas Chromatography-Mass Spectrometry and supplementary information was obtained using fourier transform-infra red and 1 H and 13 C nuclear magnetic resonance. The minimum inhibitory concentration of the purified fraction containing both the compounds was found to be 78 µg/mL. In silico molecular docking studies against the target proteins GlfT2, Inh A and mtKasB of Mycobacterium tuberculosis revealed high scores for both the compounds. Cytotoxicity studies of the compounds revealed no toxi...

Catalytic Oxidation of NO on [Au–M]− (M = Pd and Pt) Bimetallic Dimers: An Insight from Density Functional Theory Approach

The Journal of Physical Chemistry C, 2020

Escalation of nitrogen monoxide (NO) concentration into the atmosphere has caused severe environm... more

Comparative Study of Potassium Salt-Loaded MgAl Hydrotalcites for the Knoevenagel Condensation Reaction

ACS Omega, 2018

A series of potassium salt-loaded MgAl hydrotalcites were synthesized by wet impregnation of KNO ... more A series of potassium salt-loaded MgAl hydrotalcites were synthesized by wet impregnation of KNO 3 , KF, KOH, K 2 CO 3 , and KHCO 3 salts over calcined MgAl hydrotalcite (Mg−Al = 3:1). The samples were characterized by X-ray diffraction, Fourier transform infrared, thermogravimetry− differential thermal analysis, scanning electron microscopy, and N 2 absorption−desorption techniques to investigate their structural properties. The results showed formation of welldeveloped hydrotalcite phase and reconstruction of layered structure after impregnation. The prepared hydrotalcites possess mesopores and micropores having pore diameters in the range of 3.3−4.0 nm and Brunauer−Emmett−Teller surface area 90− 207 m 2 g −1. Base strengths calculated from Hammett indicator method were found increasing after loading salts, where KOH-loaded hydrotalcite showed base strength in the range of 12.7 < H − < 15, which was found to be the preferred catalyst. Subsequently, KOH loading was increased from 10 to 40% (w/w) and catalytic activity was evaluated for the Knoevenagel condensation reaction at room temperature. Density functional theory calculations show that among all of the oxygen atoms present in the hydrotalcite, the O atom attached to the K atom has the highest basic character. In this study, 10% KOH-loaded hydrotalcite showing 99% conversion and 100% selectivity was selected as the preferred catalyst in terms of base strength, stability, and catalytic efficiency.

Historical Notes- Dr. Radhikaram Dhekial Phookan: A Chemist from Assam

Indian Journal of History of Science, 2019

Radhikaram Dhekial Phookan (RDP) was the first PhD in Chemistry from Assam and probably in India.... more Radhikaram Dhekial Phookan (RDP) was the first PhD in Chemistry from Assam and probably in India. RDP's nine year hiatus at the Institute of Chemistry in the University of Heidelberg, Germany, and his publications are recorded for the first time. The faculty that taught RDP at Heidelberg, along with his mentors Robert Bunsen and Victor Meyer, presented a rare window of opportunity for a non-European to be a part of this pre-eminent centre of modern chemistry. RDP made full use of this opportunity by securing his PhD and subsequently working towards his habilitation. His work available as three publications in peer reviewed journals have been summarised in this paper. Unlike his contemporaries Acharya Sir Prafulla Chandra Ray and Sir Jagdish Chandra Bose, RPD's early demise, robbed him of the chance to play a seminal role, just when Indians were able to claim some of the limelight in natural sciences. This documentation has also cleared misconceptions related to his doctorate and its validity.

Recent Trends in the Pretreatment of Lignocellulosic Biomass for Value-Added Products

Frontiers in Energy Research, 2018

Lignocellulosic biomass (LCB) is the most abundantly available bioresource amounting to about a g... more Lignocellulosic biomass (LCB) is the most abundantly available bioresource amounting to about a global yield of up to 1. 3 billion tons per year. The hydrolysis of LCB results in the release of various reducing sugars which are highly valued in the production of biofuels such as bioethanol and biogas, various organic acids, phenols, and aldehydes. The majority of LCB is composed of biological polymers such as cellulose, hemicellulose, and lignin, which are strongly associated with each other by covalent and hydrogen bonds thus forming a highly recalcitrant structure. The presence of lignin renders the bio-polymeric structure highly resistant to solubilization thereby inhibiting the hydrolysis of cellulose and hemicellulose which presents a significant challenge for the isolation of the respective bio-polymeric components. This has led to extensive research in the development of various pretreatment techniques utilizing various physical, chemical, physicochemical, and biological approaches which are specifically tailored toward the source biomaterial and its application. The objective of this review is to discuss the various pretreatment strategies currently in use and provide an overview of their utilization for the isolation of high-value bio-polymeric components. The article further discusses the advantages and disadvantages of the various pretreatment methodologies as well as addresses the role of various key factors that are likely to have a significant impact on the pretreatment and digestibility of LCB.

Quantum mechanical study on the oxidation of ethyl vinyl ketone initiated by an OH radical

Environmental Science: Processes & Impacts, 2018

All possible reactions of EVK with OH radical along with thermochemical data (in kcal mol−1) at t... more

Modulation of the coordination environment: a convenient approach to tailor magnetic anisotropy in seven coordinate Co(ii) complexes

Chemical Communications, 2016

Subtle modulation of the coordination environment in seven coordinate Co(ii) complexes leads to a... more

Computational studies on the diffusion behaviour of alkylaromatics in large pore zeolites

Topics in Catalysis

Alkylation of aromatics over solid acid catalysts such as zeolites, has emerged in the recent pas... more Alkylation of aromatics over solid acid catalysts such as zeolites, has emerged in the recent past as a viable alternative to conventional Friedel–Crafts alkylation over environmentally hostile catalysts. We studied the diffusion behaviour of ethylbenzene (EB), isobutylbenzene (IBB), o-, m- and p-isobutylethylbenzene (IBEB) in various zeolites such as offretite (OFF), cancrinite (CAN), ZSM-12 (MTW) and ZSM-18 (MEI) by computational procedures. The periodic variations of interaction energy between the molecules and zeolite framework in the calculated diffusion energy profiles are used to predict the energy barrier for diffusion. We analyzed the results to understand the product selectivity in the formation of IBEB in the transalkylation/disproportionation reaction between IBB and EB. The results indicated that the zeolites with channel-like pores are more suitable than those with cage-like pores to achieve better selectivity. The zeolites with channels whose diameters are close to th...

Theoretical study on the gas-phase reactions of ethyl butyrate with OH radicals at 298 K

Monatshefte für Chemie - Chemical Monthly, 2014

Detailed theoretical investigation has been carried out on the mechanism, kinetics, and thermoche... more Detailed theoretical investigation has been carried out on the mechanism, kinetics, and thermochemistry of the gas-phase reactions of CH 3 CH 2 CH 2 C(O) OCH 2 CH 3 with OH radicals using a modern DFT functional. Reaction profiles are modeled with the formation of pre-and post-reactive complexes. Energetic calculations are made at M06-2X/6-31?G(d,p) level of theory. Intrinsic reaction coordinate calculation has also been performed to confirm the smooth transition from the reactant to product through the respective transition state. It has been established that the reaction proceeded via H-atom abstraction from the-CH 2 position of ethyl butyrate. The calculated rate constant using canonical transition state theory is found to be in a reasonable agreement with the experimental data. Using group-balanced isodesmic reactions, the standard heats of formation of ethyl butyrate and radicals generated by H-atom abstraction are also reported for the first time. The branching ratios of the different reaction channels are also determined. The estimated atmospheric life time of ethyl butyrate is found to be 2.37 days.

Theoretical investigation on unimolecular decomposition of malonic acid: a potential sink for ketene

RSC Advances, 2014

Structural and electronic properties of stable Lin (n=2–10) clusters: A density functional study

Physica B: Condensed Matter, 2013

The geometrical structures, relative stabilities, electronic and magnetic properties of Au n Ir 2... more The geometrical structures, relative stabilities, electronic and magnetic properties of Au n Ir 2 (n = 1-7) clusters have been systematically investigated by using meta-generalized gradient approximation (meta-GGA) Tao-Perdew-Staroverov-Scuseria (TPSS) functional in comparison with pure gold clusters. The optimized geometries show that the two doping iridium atoms can affect the structure of the host cluster. Compared with the pure Au n+2 clusters, the lowest energy Au n Ir 2 (n = 1-7) clusters favour higher spin multiplicity except for Au 7 Ir 2. Furthermore, the calculated binding energies, fragmentation energies, second-order difference energies, and the highest occupied-lowest unoccupied energy gaps indicate that the stability of Au n Ir 2 is enhanced. Natural population analysis reveals that the charges transfer from the Au n frames to the iridium atoms for Au 3,4,6,7 Ir 2 clusters. In addition, charges and magnetic moments of 6s, 5d, and 6p states for the iridium atoms in Au n Ir 2 (n = 1-7) clusters are also analyzed and compared.

Theoretical investigation of atmospheric chemistry of volatile anaesthetic sevoflurane: reactions with the OH radicals and atmospheric fate of the alkoxy radical (CF3)2CHOCHFO: thermal decomposition vs. oxidation

New J. Chem., 2014

Reaction profile (kcal mol−1) for (CF3)2CHOCHFO radical at the M06-2X/6-311++G(d,p) level.

Mechanistic and kinetics study of the gas phase reactions of methyltrifluoroacetate with OH radical and Cl atom

Molecular Physics, 2013

This article may be used for research, teaching, and private study purposes. Any substantial or s... more This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae, and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand, or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material.

Theoretical investigation on gas-phase reaction of CF3CH2OCH3 with OH radicals and fate of alkoxy radicals (CF3CH(O)OCH3/CF3CH2OCH2O)

Journal of Molecular Graphics and Modelling, 2014

Detailed theoretical investigation has been performed on the mechanism, kinetics and thermochemis... more Detailed theoretical investigation has been performed on the mechanism, kinetics and thermochemistry of the gas phase reactions of CF 3 CH 2 OCH 3 (HFE-263fb2) with OH radicals using ab-initio and DFT methods. Reaction profiles are modeled including the formation of pre-reactive and post-reactive complexes at entrance and exit channels, respectively. Our calculations reveal that hydrogen abstraction from the CH 2 group is thermodynamically and kinetically more facile than that from the CH 3 group. Using group-balanced isodesmic reactions, the standard enthalpies of formation for CF 3 CH 2 OCH 3 and radicals (CF 3 CHOCH 3 and CF 3 CH 2 OCH 2) are also reported for the first time. The calculated bond dissociation energies for the C H bonds are in good agreement with experimental results. At 298 K, the calculated total rate coefficient for CF 3 CH 2 OCH 3 + OH reactions is found to be in good agreement with the experimental results. The atmospheric fate of the alkoxy radicals, CF 3 CH(O •)OCH 3 and CF 3 CH 2 OCH 2 O • are also investigated for the first time using the same level of theory. Out of three plausible decomposition channels, our results clearly point out that reaction with O 2 is not the dominant path leading to the formation of CF 3 C(O)OCH 3 for the decomposition of CF 3 CH(O)OCH 3 radical in the atmosphere. This is in accord with the recent report of Osterstrom et al. [CPL 524 (2012) 32] but found to be in contradiction with experimental finding of Oyaro et al. [JPCA 109 (2005) 337].