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The spread of novel coronavirus strain, Severe Acute Respiratory Syndrome 2 (SARS-CoV-2) causes Coronavirus disease (COVID-19) has now spread worldwide and effecting the entire human race. The viral genetic material is transcripted and replicated by 3 C-like protease, as a result, it is an important drug target for COVID-19. Hydroxychloroquine (HCQ) report promising results against this drug target so, we perform molecular docking followed by MD-simulation studies of HCQ and modelled some ligand (Mod-I and Mod-II) molecules with SARS-CoV-2-main protease which reveals the structural organization of the active site residues and presence of a conserve water-mediated catalytic triad that helps in the recognition of Mod-I/II ligand molecules. The study may be helpful to gain a detailed structural insight on the presence of water-mediated catalytic triad which could be useful for inhibitor modelling. Communicated by Ramaswamy H. Sarma

By fluorescence spectroscopy it has been established that coal derived asphaltene (CDA) forms aggregates in CCl4 medium. The new feature of this compound is that even before aggregate formation it can incorporate water molecules and the critical aggregation concentration (CAC) in nonaqueous medium increases with increase in ω (= water:CDA mole ratio). The fluorescence spectroscopic determination of the equilibrium constant (K) of the molecular complex of [60] fullerenes with CDA in carbon tetrachloride medium has revealed that K increases on addition of microquantities of water. This observation has been rationalized by assuming that the nitrogenatoms at one end of CDA molecules attach themselves to the water micropool and thus producing a different conformation with a wider distance at the other end. This pre-organization further facilitates inclusion. By utilizing fluorescence variation of [60]fullerene/CDA complex in CCl4 as continuous medium with change in ω a critical ω (=5) has been found. The forma...

Coal-derived asphaltene (CDA) has been shown to form electron donor–acceptor-type molecular complexes with electron acceptor such as 2,5-cyclohexadiene-1,4-diylidene also known as tetracyanoquinodimethane (TCNQ) in homogeneous medium of carbon tetrachloride and heterogeneous medium of aqueous SDS. This has been investigated both by UV-Vis and fluorescence spectrophotometric method. The Charge transfer (CT) absorption peaks have been detected by difference spectral method and the wavelengths of the CT peaks are close in both the medium. The formation constants (K) have been determined using the Benesi–Hildebrand equation. The magnitudes of K are in the order of 103 L mol−1 that are comparable to some supramolecular or inclusion complexes. The study reveals the presence of π-donor (i.e., aromatic) type of compounds in CDA molecule. It also supports the view that CDA molecules exist in solution forming micellar aggregate, in the cavities of which the TCNQ molecules are included. The remarkable increase (thre...

Solvent extraction studies were carried out on the selective separation of radio-cesium from actual high level waste (HLW) using calix [4]-bis-2,3-naphtho-crown-6 (CNC) in nitrobenzene - toluene mixture. The separation studies were carried out in two stages. In the first stage, a 100 times diluted HLW was used and the purity was ascertained by gamma ray spectrometry using a HPGe detector. Quantitative separation of radio-cesium (monitored by Cs-137 gamma peak at 661 keV) was observed with almost no contamination from any of the other fission products present. In the second stage, actual HLW was used for the Cs separation study. Four stages of extraction and two stages of stripping using distilled water gave >99% recovery. About 10 mCi Cs was recovered by this method. Reusability of the solvent was also carried out and though there was no loss in selectivity, slight decrease in the extraction efficiency was observed after the reagent was allowed to be in contact with the HLW for 10 d.

Facilitated transport of uranyl ion was investigated across PTFE supported liquid membranes using T2EHDGA in n-dodecane as the carrier extractant containing 30% iso-decanol as the phase modifier. The feed was usually 3 M HNO3 while the strip phase constituted pH 2 solution. About 11 h were required for quantitative transport of U(VI) from a feed of 3 M HNO3 using 0.2 M T2EHDGA in n-dodecane containing 30% iso-decanol as the carrier extractant. Transport studies carried out using various mineral acid as feed indicated the transport trend as HNO3 >> HCl ∼ HClO4 which did not change significantly when the respective sodium salts were used in the feed. Effect of various parameters such as membrane pore size, U concentration in the feed and temperature, etc. on the transport rate was also investigated. Comparisons were made with the transport behaviour of plutonyl ion and TODGA system.

Studies on the solvent extraction and pertraction behavior of europium(III) was carried out from acidic feed solutions using N,N,N′,N′-tetra-2-ethylhexyl-3-oxapentane-diamide (T2EHDGA) in n-dodecane as the solvent. The nature of the extracted species from the solvent extraction studies conformed to Eu(NO3)3 · 3T2EHDGA which is in variance with the analogous Eu(III) – TODGA (linear homolog of T2EHDGA) extraction system. The transport behavior of Eu(III) was investigated from a feed containing 3.0 M HNO3 into a receiver phase containing 0.01 M HNO3 across a PTFE flat sheet supported liquid membrane (SLM) containing 0.2 M T2EHDGA in n-dodecane as the carrier solvent and 30% iso-decanol as the phase modifier. Effects of feed acidity, carrier extractant concentration, membrane pore size, and Eu concentration in the feed on the transport rates of Eu(III) were also investigated. Membrane diffusion coefficient (D o) for the pertracted species was calculated using the Wilke-Chang equation as 4.25 × 10−6 cm2 · s−1....

Transport of Pu3+ across PTFE flat sheet supported liquid membranes (SLM) using N,N,N′,N′-tetraoctyl-3-oxapentanediamide (TODGA) in n-dodecane as the carrier extractant was investigated. The feed solution was usually 3.0 M HNO3 while the receiver phase contained 0.1 M HNO3. In order to model the transport data, the two-phase liquid-liquid extraction experiments are also reported. A series of reducing agents viz. hydrazinium nitrate (HN), phenyl hydrazine (PH), hydroxyl ammonium nitrate (HAN), and ascorbic acid (AA) were evaluated to maintain plutonium in the +3 state in the feed, out of which phenyl hydrazine was found to be the most effective. Effectiveness of various strippants for quantitative and rapid transport of Pu was also evaluated. Additionally, the effects of feed acidity, carrier concentration, membrane thickness, effect of Pu carrier concentration, etc. were investigated. Membrane diffusion co-efficients were calculated and found to be 1.47 × 10−6 cm2/s for Pu(III). The stability of the SLM, ...

The transport behavior of Th4+ was investigated from a feed containing 3.0 M HNO3 into a receiver phase containing 0.1 M oxalic acid across a PTFE flat sheet supported liquid membrane (SLM) which contained TODGA (N,N,N′,N′-Tetraoctyl-3-oxapentanediamide) in n-dodecane as the extractant. Effects of the nature of the strippant, extractant concentration, Th concentration in the feed, and feed acidity on the transport rates were investigated. The transport behavior apparently depended on the rate of extraction of the metal ion at the feed-membrane interface and was not diffusion controlled. Influence of Th concentration on flux was also investigated. Transport mechanism was elucidated and the diffusion coefficient was calculated to be 2.13 × 10−7 cm2/s. Solvent extraction studies at varying feed acidity and TODGA concentration were also carried out.

The present paper describes the results of solvent extraction studies carried out in batch mode to collect data on distribution of uranium, plutonium, and thorium using 5% TBP in n-dodecane. Extraction studies are carried out from feed solutions having bulk thorium containing aluminum and fluoride ions in ∼3.00–4.00 M nitric acid at concentration levels anticipated in feed solutions during Advanced Heavy Water Reactor (AHWR) spent fuel reprocessing. Studies are carried out under varied experimental conditions. Parameters such as organic to aqueous phase ratio during extraction, concentration of nitric acid for scrubbing co-extracted thorium from loaded organic phase etc., are studied in detail. Hydroxylamine nitrate is selected for reductive stripping of plutonium in preliminary studies. Reagent mixture containing 0.30 M HAN + 0.60 M HNO3 and 0.20 M N2H4 is found to be optimum for plutonium partitioning. This paper also describes the extraction and stripping of uranium and plutonium in co-current mode. Th...

The extraction of Pu(IV) from nitric acid medium using TBP has been compared with two diluents using n-dodecane and a RTIL, 1-butyl-3-methylimidazolium bis(trifluoromethanesulphonyl)imide (C4mimTf2N). Kinetics of extraction was slower in RTIL compared to n-dodecane. The mechanism of extraction was found to be cation exchange at lower acidity which changes to the formation of a neutral complex at higher acidity greater than 1M HNO3 for RTIL. Back extraction of Pu from the loaded organic phase was equally effected using 0.1M oxalic acid and a mixture of guanidine carbonate and EDTA as strippant from both the extraction systems under study. Radiation stability and reusability studies showed promise for future application.