Chemical Engineering

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CD4-mimetic HIV-1 entry inhibitors are small sized molecules which imitate similar conformational flexibility, in gp120, to the CD4 receptor. However, the mechanism of the conformational flexibility instigated by these small sized inhibitors is little known. Likewise, the effect of the antibody on the function of these inhibitors is also less studied. In this study, we present a thorough inspection of the mechanism of the conformational flexibility induced by a CD4-mimetic inhibitor, NBD-557, using Molecular Dynamics Simulations and free energy calculations. Our result shows the functional importance of Asn425 in substrate induced conformational dynamics in gp120. The MD simulations of Asn425Gly mutant provide a less dynamic gp120 in the presence of NBD-557 without incapacitating the binding enthalpy of NBD-557. The MD simulations of complexes with the antibody clearly show the enhanced affinity of NBD-557 due to the presence of the antibody, which is in good agreement with experimental Isothermal Titration Calorimetry results (Biochemistry2006, 45, 10973-10980).

(SoE) School of Engineering

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Chemistry

(SoNS) School of Natural Sciences

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Molecules (Basel, Switzerland)

Does Antibody Stabilize the Ligand Binding in GP120 of HIV-1 Envelope Protein? Evidence from MD Simulation

We report experimental evidence of circulation reversal in evaporating drops. The internal flow patterns and particle distribution inside the evaporating water droplet with suspended polystyrene particles was studied using the Particle Image Velocimetry (PIV) technique. Droplet placed on externally heated substrate showed two symmetric and counter rotating Marangoni convection cells at the beginning of evaporation process. Towards the final stages of evaporation, the two counter rotating Marangoni convection cells reversed the direction of circulation. Interestingly, it was observed that between these two stages four symmetric and counter rotating convection cells appeared inside the evaporating droplet. Our results are in support of recent theoretical investigations on circulation reversal in evaporating drops. The flow patterns were driven by the surface tension gradient caused by the surface temperature distribution along the droplet-air interface. The surface temperature distribution is not only dependent on the non-uniform evaporation flux but also on the conduction path from the substrate to the droplet surface. Towards the end of evaporation, the fluid flow becomes radially outward from the center to the pinned edge of the droplet. We have also investigated the evaporating droplets placed on a curved substrate. Unlike the case of flat substrate, the evaporation from curved surface resulted monotonic temperature profile. The particle distribution and resulting deposition patterns was strongly influenced by the internal fluid flow pattern and was observed to be different from that of a flat substrate. © 2021, The Author(s), under exclusive licence to Springer Nature B.V. part of Springer Nature.

Microgravity Science and Technology

Analysis of Circulation Reversal and Particle Transport in Evaporating Drops

The present article emphasizes the synthesis of Schiff base derived bis(1,2,3-triazolyl-γ-propyltriethoxysilanes) (3a-3d) by utilizing an efficient and biocompatible Cu(I) catalyzed 'Click Chemistry' approach. All the synthesized compounds 3a-3d have been well-characterized by IR, NMR (1H and 13C) and HRMS spectroscopic techniques. Further, 3a was immobilized over silica nanosphere and the resultant hybrid nanoparticles were thoroughly examined by IR, XRD, EDX, TGA, and SEM analysis. The photophysical properties of 3a and their hybrid nanoparticles were studied which showed dual recognition of Cu2+ and Fe3+ ions with negligible interference from other metal ions. Most importantly, hybrid nanoparticles have strong binding affinity towards Cu2+ and Fe3+ compared to compound 3a. All types of the binding interaction between chemosensors and metal ions, Cu2+ and Fe3+ got reversed upon addition of Na2EDTA. The interacting behaviour of 3a towards Cu2+ and Fe3+ ions has been studied by performing DFT calculations. © 2020 Elsevier B.V.

Inorganica Chimica Acta

Schiff base derived bis-organosilanes: Immobilization on silica nanosphere and Cu2+ and Fe3+ dual ion sensing

In this work, the steam gasification of mixed food waste was carried out with torrefaction as pretreatment. Torrefaction was carried out at various temperatures; 230 °C, 260 °C, and 290 °C and for one-hour residence time. Improvement in physico-chemical properties of food waste by torrefaction was studied using proximate, elemental, and compositional analysis. Additionally, the effect of torrefaction on mass yield, energy yield, mass density and energy density was presented. Gasification was then carried out using torrefied food waste as biomass with steam as a gasification agent at 700 °C. The steam flow rate was kept at 0.625 mL/min with a steam to biomass ratio of 1.25. The resulting syngas was characterized for syngas yield, syngas composition, H2yield, and high heating value (HHV). It was found that syngas yield and H2field varied from 0.95 to 3.49 m3/Kg and 0.6 to 2.15 m3/Kg respectively from gasification of food waste torrefied at different temperatures. The highest HHV of syngas was found to be 12.19 MJ/Nm3. Cold gas efficiency and carbon conversion efficiency were also determined to evaluate the performance of proposed pretreatment on steam gasification. © 2020 Georg Thieme Verlag. All rights reserved.

Journal of Environmental Chemical Engineering

Steam gasification with torrefaction as pretreatment to enhance syngas production from mixed food waste

Hydrogen production from food waste by biochemical and thermochemical methods is reviewed herein. Generally, fermentation, a biochemical method, is considered to be more suitable for hydrogen production from food waste, and the performance of fermentation units depends on many factors, e.g., substrate composition, type of pretreatment, reactor configuration, and operating parameters, e.g., organic loading rate, hydraulic retention time, pH, and temperature. Controlling so many factors is tedious, expensive, and results in a slow process. On the other hand, thermochemical methods involve fewer factors and steps, can be much faster and less costly, and can also be used for efficient hydrogen production from food waste. Steam gasification has produced good hydrogen yields from raw food waste. © 2021 Wiley-VCH GmbH

Chemical Engineering and Technology

Biochemical and Thermochemical Routes of H2 Production from Food Waste: A Comparative Review

More than thirty-five years ago, the Bhopal disaster shook the whole world and investigators found out that many people survived just because they turned on the fans in their bedrooms. It was postulated that the forced ventilation played an important role in diluting the toxic gas and saved these people. In order to provide evidence to solve this old mystery, this research employed FLACS software to assess the hazardous degree of a toxic gas (hydrogen sulfide) leakage within a petrochemical process. Series of gas dispersion simulations were performed to actualize the hazardous characteristics and the corresponding risks of the release accident. The study shows that the hazardous level and the hazard range can be greatly influenced when parameters, such as the gas leakage circumstances (atmospheric conditions and wind speed) and the mitigation measures (direction of fans and their speed) are altered. By using explosion-proof fans in different positions and ventilation directions, combined with the natural wind in a certain direction, this research attempts to detect the best combination from various mitigation designs and to compare the influence of fan directions on hazard mitigation. It is also the first time of its kind to simulate the effect of forced ventilation on hazard mitigation within a process plant. The results show that the hazardous level of a toxic release can be effectively alleviated, when the direction of the mechanical ventilation is against the natural wind direction. With the help of the CFD simulation and the quantitative risk analysis technique, different loss prevention strategies can be tested via this method in order to establish a safer working environment. © 2020 Elsevier Ltd

Journal of Loss Prevention in the Process Industries

A preliminary explore to the forced ventilation on the toxic gas release/dispersion and the hazard mitigation within a petrochemical plant

L-asparaginase is a cardinal biotherapeutic drug for treating acute lymphoblastic leukemia, which is highly prevalent in children worldwide. In the current investigation, L-asparaginase producing marine bacterial isolate, Bacillus australimaris NJB19 (MG734654), was observed to be producing extracellular glutaminase free L-asparaginase (13.27 ± 0.4 IU mL−1). Production of L-asparaginase was enhanced by the Box-Behnken design approach that enumerated the significant variables affecting the enzyme production. The optimum levels of the derived variables resulted in 2.8-fold higher levels of the enzyme production (37.93 ± 1.06 IU mL−1). An 1146 bp L-asparaginase biosynthetic gene of Bacillus australimaris NJB19 was identified and cloned in E. coli DH5α, fused with a histidine tag. The in silico analysis of the protein sequence revealed the presence of a signal peptide and classified it as a type II L-asparaginase. Toxic peptide prediction disclosed no toxin domain in the protein sequence, hence suggesting it as a non-toxic protein. The secondary structure analysis of the enzyme displayed a comparable percentage of alpha-helical and random coil structure, while 14.39\% and 6.57\% of amino acid residues were composed of extended strands and beta-turns, respectively. The functional sites in the three-dimensional structural model of the protein were predicted and interestingly had a few less conserved residues. Bacillus australimaris NJB19 identified in this study produces type-II L-asparaginase, known for its high affinity for asparagine and effectiveness against leukemic cells. Hence, these observations indicate the L-asparaginase, thus obtained, as a potentially significant and novel therapeutic drug. © 2021 Elsevier B.V.

International Journal of Biological Macromolecules

A potential type-II L-asparaginase from marine isolate Bacillus australimaris NJB19: Statistical optimization, in silico analysis and structural modeling

The effectiveness of CO2 absorption in ionic liquids (ILs) depends on the physical properties of cations/anions of the IL and their influence on ion-ion and ion-CO2 interactions. A molecular understanding of these cation-anion and ion-CO2 interactions is vital to identify promising ILs for CO2 capture. Koopmans' theorem based on quantum mechanics was used to compute several interaction descriptors, such as ionization potential (IP), electron affinity (EA), chemical potential, chemical hardness, softness, and electrophilicity index for cations/anions/ILs. Density Functional Theory (DFT) studies were performed to obtain interaction energies (IE) for ion-ion and ion-CO2 interactions. Several cations (imidazolium-based and pyridinium-based), inorganic (F¯, BF4¯, etc.) and organic anions ([TF2N]¯, [bFAP]¯, etc.) and cation-anion combinations were considered in the present study. The analysis of different interaction descriptors provided a better understanding of the relationships between the EA of cation, the IP of anion, and cation-anion IE values with the experimental CO2 solubility. Several inferences can be made based on the results obtained: a) the cation-anion interaction energy and IP of the anion have a strong correlation with the CO2 solubility, b) the IE trends of ion-CO2 and CO2-IL alone do not correlate well with the experimental CO2 solubility trends, (c) free molecular volume or interstitial spaces resulting from entropic effects of cation-anion interactions due to the nature/structure of cation and anion, play a dominant role for an effective CO2 absorption, (d) for a particular anion, changing the cation does not significantly influence cation-anion IE and ion-CO2 IE values, while for a particular cation, the nature of anion dramatically influences cation-anion IE and ion-CO2 IE values – consistent with the experimental CO2 solubility trends. Of the anions and cations studied, the combination of anions containing fluoroalkyl groups, such as [TF2N]¯ and [bFAP]¯, with the cations, such as [hmim]+ and [hmpy]+ constitute promising solvents for efficient CO2 capture. The findings of this study emphasize the importance of assessing cation-anion and ion-CO2 interactions in conjunction with other interaction descriptors to design efficient solvents for CO2 capture. © 2020

Journal of Molecular Liquids

Molecular understanding of carbon dioxide interactions with ionic liquids

Silica Nanoparticles (SiNPs), due to its tunable properties and composition, meets the needs in specified applications. Rice Husk (RH), an agricultural waste, abundant in amorphous silica has its extensive application in various industrial products. However, the presence of impurities in RHs makes the extraction process difficult and optimum experimental conditions are needed to achieve maximum yield with specific properties for its specified applications. In this work, Rice Husk Ash (RHA) is prepared from RH by acid leaching followed by silica gel extraction from RHA via controlled pyrolysis at three temperatures (700°C, 750°C and 800°C). Pyrolyzed RHA is then dried and pulverized to get SiNPs. Characterization of SiNPs is done using UV-Vis Spectroscopy, X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). UV-Vis Spectroscopy and XRD analysis shows that the SiNPs extracted from RHA at 750°C exhibited the highest peak at 260 nm and 2θ=26° respectively and XRD and SEM analysis show that crystallite and particle size is in close agreement with each other. The optimum temperature being 750°C, silica gel formed at a pH 6 is more stable, transparent and thicker in comparison to the silica gel formed at varied pH. Moreover, the sodium silicate sample exhibits a bright green fluorescence and the intensity of fluorescence is higher for the sodium silicate prepared at 750°C range than at any other temperature. © 2020 Scientific Publishers. All rights reserved.

Journal of Scientific and Industrial Research

Extraction of silica nanoparticles from Rice Husk Ash and its characterization

In this study, the extraction of carrot seed oil is carried out using supercritical CO2. Screening design was applied on operating parameters such as pressure, temperature, solvent flow rate, particle size and co-solvent to study the contribution of each parameter on extraction yield. Central composite design is employed on reduced parameters with operating ranges: 20–40 MPa (pressure), 50–70 °C (temperature), 5–15 g/min (solvent flow rate) and 0–10 wt\% (co-solvent). Extraction yield is varied from 2.8 to 12.9 wt\% of carrot seed. Experimental data are fitted well in the least-square regression model where optimized conditions are found as 40 MPa, 70 °C, 8.53 g/min and 5.87 wt\% corresponding to the maximum yield of 13.5 wt\%. Analysis of oil reveals the presence of saturated and unsaturated fatty acids. Principle fatty acid of carrot seed oil, i.e., oleic acid, is also optimized to maximize its extraction. The industrial-scale economic assessment is performed to study the feasibility of the supercritical fluid extraction of carrot seed oil. © 2019, Islamic Azad University (IAU).