Formation and Transformation of Clathrate Hydrates under Interstellar Conditions.

ConspectusContinuing efforts by many research groups have led to the discovery of ∼240 species in the interstellar medium (ISM). Observatory- and laboratory-based astrochemical experiments have led to the discovery of these species, including several complex organic molecules (COMs). Interstellar molecular clouds, consisting of water-rich icy grains, have been recognized as the primordial sources of COMs even at extremely low temperatures (∼10 K). Therefore, it is paramount to understand the chemical processes of this region, which may contribute to the chemical evolution and formation of new planetary systems and the origin of life.This Account discusses our effort to discover clathrate hydrates (CHs) of several molecules and their structural varieties, transformations, and kinetics in a simulated interstellar environment. CHs are nonstochiometric crystalline host-guest complexes in which water molecules form cages of different sizes to entrap guest molecules. CHs are abundant on earth and require moderate temperatures and high pressures for their formation. Our focus has been to form CHs at extremely low pressure and temperature as in the ISM, although their existence under such conditions has been a long-standing question since water and guest molecules (CH4, CO2, CO, etc.) exist in space. In multiple studies conducted at ∼10-10 mbar, we showed that CH4, CO2, and C2H6 hydrates could be formed at 30, 10, and 60 K, respectively. Well-defined IR spectroscopic features supported by quantum chemical simulations and temperature-programmed desorption mass spectrometric analyses confirmed the existence of the 512 (for CH4 and CO2) and 51262 (for C2H6) CH cages. Mild thermal activation for long periods under ultrahigh vacuum (UHV) allowed efficient molecular diffusion, which is crucial for forming CHs. We also explored the formation of THF hydrate (a promoter/stabilizer for binary CHs), and a spontaneous method was found for its formation under UHV. In a subsequent study, we observed a binary THF-CO2 hydrate and its thermal processing at 130 K leading to the transportation of CO2 from the hydrate cages to the matrix of amorphous water. The findings imply that such systems possess a dynamic setting that facilitates the movement of molecules, potentially accounting for the chemical changes observed in the ISM. Furthermore, an intriguing fundamental phenomenon is the consequences of these CHs and their dynamics. We showed that preformed acetone and formaldehyde hydrates dissociate to form cubic (Ic) and hexagonal (Ih) ices at 130-135 K, respectively. These unique processes could be the mechanistic routes for the formation of various ices in astrophysical environments.Other than adding a new entry, namely, CHs, to the list of species found in ISM, its existence opens new directions to astrochemistry, observational astronomy, and astrobiology. Our work provides a molecular-level understanding of the formation pathways of CHs and their transformation to crystalline ices, which sheds light on the chemical evolution of simple molecules to COMs in ISM. Furthermore, CHs can be potential candidates for studies involving radiation, ionization, and electron impact to initiate chemical transformations between the host and guest species and may be critical in understanding the origin of life.

Induced Migration of CO2 from Hydrate Cages to Amorphous Solid Water under Ultrahigh Vacuum and Cryogenic Conditions.

Restricted migration of reactive species limits chemical transformations within interstellar and cometary ices. We report the migration of CO2 from clathrate hydrate (CH) cages to amorphous solid water (ASW) in the presence of tetrahydrofuran (THF) under ultrahigh vacuum (UHV) and cryogenic conditions. Thermal annealing of sequentially deposited CO2 and H2O ice, CO2@H2O, to 90 K resulted in the partitioning of CO2 in 512 and 51262 CH cages (CO2@512, CO2@51262). However, upon preparing a composite ice film composed of CO2@512, CO2@51262 and THF distributed in the water matrix at 90 K, and annealing the mixture for 6 h at 130 K produced mixed CO2-THF CH, where THF occupied the 51264 cages (THF@51264) exclusively while CO2 in 51262 cages (CO2@51262) got transferred to the ASW matrix and CO2 in the 512 cages (CO2@512) remained as is. This cage-matrix exchange may create a more conducive environment for chemical transformations in interstellar environments.

Machine Learning in Drug Metabolism Study.

Metabolic reactions in the body transform the administered drug into metabolites. These metabolites exhibit diverse biological activities. Drug metabolism is the major underlying cause of drug overdose-related toxicity, adversative drug effects and the drug's reduced efficacy. Though metabolic reactions deactivate a drug, drug metabolites are often considered pivotal agents for off-target effects or toxicity. On the other side, in combination drug therapy, one drug may influence another drug's metabolism and clearance and is thus considered one of the primary causes of drug-drug interactions. Today with the advancement of machine learning, the metabolic fate of a drug candidate can be comprehensively studied throughout the drug development procedure. Naïve Bayes, Logistic Regression, k-Nearest Neighbours, Decision Trees, different Boosting and Ensemble methods, Support Vector Machines and Artificial Neural Network boosted Deep Learning are some machine learning algorithms which are being extensively used in such studies. Such tools are covering several attributes of drug metabolism, with an emphasis on the prediction of drug-drug interactions, drug-target-interactions, clinical drug responses, metabolite predictions, sites of metabolism, etc. These reports are crucial for evaluating metabolic stability and predicting prospective drug-drug interactions, and can help pharmaceutical companies accelerate the drug development process in a less resource-demanding manner than what in vitro studies offer. It could also help medical practitioners to use combinatorial drug therapy in a more resourceful manner. Also, with the help of the enormous growth of deep learning, traditional fields of computational drug development like molecular interaction fields, molecular docking, quantitative structure-to-activity relationship (QSAR) studies and quantum mechanical simulations are producing results which were unimaginable couple of years back. This review provides a glimpse of a few contextually relevant machine learning algorithms and then focuses on their outcomes in different studies.

Facile Synthesis of Triazoles using Electrospray-Deposited Copper Nanomaterials to Catalyze Azide-Alkyne Cycloaddition (AAC) Click Reactions.

Electrospray deposition of copper salt-containing microdroplets onto the liquid surface of an electrically grounded reaction mixture leads to the formation of Cu nanoclusters, which then catalyze the azide-alkyne cycloaddition (AAC) reaction to form triazoles. This method of in situ nanocatalyst preparation provided 17 times higher catalytic activity compared to that in the conventional catalytic reaction. The gentle landing of the Cu-containing droplets onto the liquid surface forms a thin film of catalyst which promotes the heterogeneous AAC reaction while showing diffusion-controlled kinetics. UV-vis spectral characterization confirms that the catalyst is comprised of Cu nanoclusters. This unique catalytic strategy was validated using several substrates and the corresponding products were confirmed by tandem mass spectrometry (MS/MS) analysis.

Accelerated and Concerted Aza-Michael Addition and SuFEx Reaction in Microdroplets in Unitary and High-Throughput Formats.

The sulfur fluoride exchange (SuFEx) reaction is significant in drug discovery, materials science, and chemical biology. Conventionally, it involves installation of SO2 F followed by fluoride exchange by a catalyst. We report catalyst-free Aza-Michael addition to install SO2 F and then SuFEx reaction with amines, both occurring in concert, in microdroplets under ambient conditions. The microdroplet reaction is accelerated by a factor of ∼104 relative to the corresponding bulk reaction. We suggest that the superacidic microdroplet surface assists SuFEx reaction by protonating fluorine to create a good leaving group. The reaction scope was established by performing individual reactions in microdroplets of 18 amines in four solvents and confirmed using high-throughput desorption electrospray ionization experiments. The study demonstrates the value of microdroplet-assisted accelerated reactions in combination with high-throughput experimentation for characterization of reaction scope.

Late-Stage Functionalization and Characterization of Drugs by High-Throughput Desorption Electrospray Ionization Mass Spectrometry.

Late-stage functionalization (LSF) of drug molecules is an approach to generate modified molecules that retain functional groups present in the active drugs. Here, we report a study that seeks to characterize the potential value of high-throughput desorption electrospray ionization mass spectrometry (HT DESI-MS) for small-scale rapid LSF. In conventional route screening, HT-based DESI-MS provides contactless, rapid analysis, reliable and reproducible data, minimal sample requirement, and exceptional tolerance to high salt concentrations. Ezetimibe (E), an established hypertension drug, is targeted for modification by LSF. C-H alkenylation and azo-click reactions are utilized to explore this approach to synthesis and analytical characterization. The effect of choice of reactant, stoichiometry, catalyst, and solvent are studied for both reactions using high throughput DESI-MS experiments. Optimum conditions for the formation of LSF products are established with identification by tandem mass spectrometry (MS/MS).

Organic Zinc and Copper Supplementation-Associated Changes in Gene Expression and Protein Profiles in Buck Spermatozoa.

Mineral supplementation has greater impact on male reproduction; however, the mechanism of action has not been studied in detail. The present study was aimed to deal with the lacuna in mechanism of action of mineral supplementation on improvement in sperm characteristics. A group of 40 bucks (aged 5 months) were assigned to 10 groups (4 in each group) based on their body weight and fed with concentrate mixture: basal roughage (minimal diet) in equal proportion to all the bucks. Among the 10 groups, one was considered as control, without any additional mineral supplementation, and the remaining 9 were treatment groups (3 groups each in Zn, Cu, and Zn + Cu). In treatment groups, organic Zn was fed in three different doses as 20, 40, and 60 mg/kg DM; organic Cu was fed in three different doses as 12.5, 25, and 37.5 mg/kg DM; and organic Zn + Cu was combinedly supplied as 20 + 12.5, 40 + 25, and 60 + 37.5 based on their mg/kg DM for 8 months period. The neat semen samples were processed for spermatozoal gene (stress- NOS3, HSP70, HIF1A; fertility- MTF1, MTA1, TIMP2, TNFa, and EGFR) expression studies through qRT-PCR and protein profile changes through single- and two-dimensional gel electrophoresis. Significantly, the stress-responsive genes were downregulated, and fertility-related genes were upregulated in treatment groups. A significant correlation had been noticed among the genes studied: HIF1A with MTA1 (P < 0.05) and MTF1 with EGFR, TIMP2, TNFa, and NOS3 (P < 0.01) respectively. The organic Zn and Cu feeding modulated the expression of stress- and fertility-related genes and protein abundance, thereby improved the sperm characteristics.

Desorption-induced evolution of cubic and hexagonal ices in an ultrahigh vacuum and cryogenic temperatures.

Reflection absorption infrared spectroscopic investigations of multilayer films of acetonitrile (ACN) and water in an ultrahigh vacuum under isothermal conditions showed the emergence of cubic (ice Ic) and hexagonal (ice Ih) ices depending on the composition of the film. The experiments were conducted with a mixed film of 300 monolayers in thickness and the ACN : H2O monolayer ratios were varied from 1 : 5 to 5 : 1. Mixed films were deposited at 10 K and warmed to 130-135 K, where ACN desorbed subsequently and IR spectral evolution was monitored continuously. While the emergence of ice Ic at 130 K has been reported, the occurrence of ice Ih at this temperature was seen for the first time. Detailed investigations showed that ice Ih can form at 125 K as well. Crystallization kinetics and activation energy (Ea) for the emergence of ice Ih were evaluated using the Avrami equation.

Sociodemographic and clinical profile of drug treatment seekers attending the State Psychiatric Hospital and Drug De-addiction Center at Agartala, Tripura.

BACKGROUND: Substance use disorders have become a widespread public health problem, especially in the northeastern states, and limited studies have been undertaken to reflect the picture of the same. AIMS: The aim of the study was to study the sociodemographic and clinical profile of drug treatment seekers attending a State Psychiatric Hospital and De-addiction Center of Northeastern India. MATERIALS AND METHODS: It was a cross-sectional hospital-based study conducted from October 2018 to August 2019. Two hundred and ten consecutive treatment-seeking patients, fulfilling inclusion and exclusion criteria and diagnosed with the International Classification of Diseases version 10 for substance dependence, were included in the study. RESULTS: Most common abused drug was opioids (42.9%), followed by alcohol (14.3%), whereas 29.0% were people who inject drugs. Peer pressure in 55.2% and curiosity in 32.9% were reported to be the most common causes for initiating substances. Hepatitis C was the most common (52.4%) comorbidity related to intravenous drug users. CONCLUSIONS: Results of the current study will definitely encourage further large-scale community-level studies to assess the prevalence of substance abuse in the state as well as in drug policymaking.

Osteogenic differentiation potential of porcine bone marrow mesenchymal stem cell subpopulations selected in different basal media.

Multipotent porcine mesenchymal stem cells (pMSC) are invaluable for research and therapeutic use in regenerative medicine. Media used for derivation and expansion of pMSC may play an important role for the selection of MSC subpopulation at an early stage and thereby, the specific basal medium may also affect differentiation potential of these cells. The present study was undertaken to evaluate the effects of αMEM, aDMEM, M199, αMEM/M199, aDMEM/M199 and αMEM/aDMEM media on (1) porcine bone marrow MSC derivation; (2) expression of number of osteogenic markers (ALP, COL1A1, SPP1 and BGLAP) at 5th and 10th passage in pMSC before differentiation; and (3) differentiation of pMSC (at 5th passage) to osteogenic lineage. Morphological changes and matrix formation in osteogenic cells were evaluated by microscopic examination. Calcium deposits in osteocytes were confirmed by Alizarin Red S staining. Based on expression of different markers, it was evident that selection of bone marrow pMSC subpopulations was independent of basal media used. However, the differentiation of those pMSCs, specifically to osteogenic lineage, was dependent on the medium used for expansion of pMSC at the pre-differentiation stage. We demonstrated here that the pMSC grown in combined αMEM/aDMEM (1:1) medium expressed number of osteogenic markers and these pMSC underwent osteogenic differentiation most efficiently, in comparison to porcine mesenchymal stem cells grown in other media. In conclusion, osteogenic differentiation potential of pMSC maintained in αMEM/aDMEM medium was observed significantly higher compared to cells cultivated in other media and therefore, the combined medium αMEM/aDMEM (1:1) may preferentially be used for expansion of pMSC, if needed for osteogenic differentiation.

Iron assisted formation of CO2 over condensed CO and its relevance to interstellar chemistry.

Catalytic conversion of CO to CO2 has been investigated in ultrahigh vacuum (UHV) under cryogenic conditions (10 K). This cryogenic oxidation is assisted by iron upon its co-deposition with CO, on a substrate. The study shows that the interaction of Fe and CO results in a Fe-CO complex that reacts in the presence of excess CO at cryogenic conditions leading to CO2. Here, the presence of CO on the surface is a prerequisite for the reaction to occur. Different control experiments confirm that the reaction takes place in the condensed phase and not in the gas phase. Surface sensitive reflection absorption infrared spectroscopy (RAIRS), temperature programmed desorption (TPD), and Cs+ based low energy ion scattering are utilized for this study. The iron assisted formation of CO2 may be proposed as another pathway relevant in interstellar ices, containing CO. This direct oxidation process, which occurs at extremely low temperatures and pressures, in the presence of a reactive metal species like iron (the most abundant metal in the interstellar medium) may have astrochemical importance. It does not require any external energy in the form of photo-irradiation or thermal processing. Such reactions are highly relevant in cold dense molecular clouds where interactions between neutral species are more favoured.

Nonenzymatic Glucose Sensing Using Ni60Nb40 Nanoglass.

Despite being researched for nearly five decades, chemical application of metallic glass is scarcely explored. Here we show electrochemical nonenzymatic glucose-sensing ability of nickel-niobium (Ni60Nb40) amorphous alloys in alkaline medium. Three different Ni60Nb40 systems with the same elemental composition, but varying microstructures are created following different synthetic routes and tested for their glucose-sensing performance. Among melt-spun ribbon, nanoglass, and amorphous-crystalline nanocomposite materials, nanoglass showed the best performance in terms of high anodic current density, sensitivity (20 mA cm-2 mM-1), limit of detection (100 nM glucose), stability, reproducibility (above 5000 cycles), and sensing accuracy among nonenzymatic glucose sensors involving amorphous alloys. When annealed under vacuum, only the heat-treated nanoglass retained a similar electrochemical-sensing property, while the other materials failed to yield desired results. In nanoglass, a network of glassy interfaces, compared to melt-spun ribbon, is plausibly responsible for the enhanced sensitivity.

Formation of Cubic Ice via Clathrate Hydrate, Prepared in Ultrahigh Vacuum under Cryogenic Conditions.

Cubic ice (ice Ic) is a crystalline phase of solid water, which exists in the earth's atmosphere and extraterrestrial environments. We provide experimental evidence that dissociation of acetone clathrate hydrate (CH) makes ice Ic in ultrahigh vacuum (UHV) at 130-135 K. In this process, we find that crystallization of ice Ic occurs below its normal crystallization temperature. Time-dependent reflection absorption infrared spectroscopy (RAIRS) and reflection high-energy electron diffraction (RHEED) were utilized to confirm the formation of ice Ic. Associated crystallization kinetics and activation energy (Ea) for the process were evaluated. We suggest that enhanced mobility or diffusion of water molecules during acetone hydrate dissociation enabled crystallization. Moreover, this finding implied that CHs might exist in extreme low-pressure environments present in comets. These hydrates, subjected to prolonged thermal annealing, transform into ice Ic. This unique process of crystallization hints at a possible mechanistic route for the formation of ice Ic in comets.

Buffalo early pregnancy biomarker coding sequence cloning and partial length expression in E. coli after codon optimization.

Pregnancy-associated glycoproteins (PAGs) secreted from conceptus specific trophoblast cells are widely accepted biomarkers of ruminants. Limited information of PAGs in buffalo warrants further investigation for the development of sensitive homologous early pregnancy-specific diagnostic immunoassay. This experiment was thus designed to identify and clone the predominantly expressed early placentome-specific buffalo PAG (buPAG) isoform; to express this PAG isoform and verify its antigenicity by developing antisera and testing immuno-reactivity with recombinant proteins. Results indicated PAG 7 (buPAG 7) was the predominant isoform in buffalo early pregnant placentome. Attempt to express the full native glycosylated protein in the pcDNA3.3 vector and FreeStyle HEK 293F host was not successful. However, a partial 124 amino acid sequence selected from the non-glycosylated region of buPAG 7 could be expressed in E. coli BL21 (DE3) cells after codon optimization however; the yield was low. Antigenicity of the expressed protein was confirmed by successful immuno-reaction in rabbits indicating possibilities of using 124 aa partial PAG 7 protein as a putative antigen for monoclonal antibody production and development sensitive homologous immunoassay. In conclusion, our results confirmed the findings that buPAG 7 as the predominant early pregnancy-specific transcript. A selected partial 124 amino acid sequences of it could even be expressed in a heterologous host (E. coli). Based on our data presented here, we anticipate that the expressed recombinant protein can be useful as an antigen suitable for the development of PAG specific immunoassays in buffalo.

Lupeol alters viability of SK-RC-45 (Renal cell carcinoma cell line) by modulating its mitochondrial dynamics.

Renal cell carcinoma (RCC) is the most common kidney cancer leading to 140,000 deaths per year. Among all RCCs 80% evolve from the epithelial proximal tubular cells within the kidney. There is a high tendency of developing chemoresistance and resistance to radiation therapy in most RCC patients. Therefore, kidney resection is considered as the most effective treatments for patients having localized RCC. There is a high tendency of post-operative recurrence among 20-40% of the patients and this recurrence is not curable. It is also clear that modern medicine has no curative treatment options against metastatic RCC. Lupeol [lup-20(29)-en-3ß-ol] is a pentacyclic triterpenoid compound naturally found in various edible fruits and in many traditionally used medicinal plants, and has been demonstrated as effective against highly metastatic melanoma and prostate cancers. The present study was designed to evaluate the effect of lupeol to RCC with molecular details. Treatment with lupeol on SK-RC-45 (a RCC cell line) with the LC50 dose of 40µM (for 48 h) induces mitochondrial hyper fission which eventually leads to apoptosis while SK-RC-45 counteracts by enhancing autophagy-mediated selective removal of fragmented mitochondria. This is the first study which concurrently reports the effects of lupeol on RCC and its effect on the mitochondrial dynamics of a cell. Herein, we conclude that lupeol has potential to be an effective agent against RCC with the modulation of mitochondrial dynamics.

Clathrate hydrates in interstellar environment.

Clathrate hydrates (CHs) are ubiquitous in earth under high-pressure conditions, but their existence in the interstellar medium (ISM) remains unknown. Here, we report experimental observations of the formation of methane and carbon dioxide hydrates in an environment analogous to ISM. Thermal treatment of solid methane and carbon dioxide-water mixture in ultrahigh vacuum of the order of 10-10 mbar for extended periods led to the formation of CHs at 30 and 10 K, respectively. High molecular mobility and H bonding play important roles in the entrapment of gases in the in situ formed 512 CH cages. This finding implies that CHs can exist in extreme low-pressure environments present in the ISM. These hydrates in ISM, subjected to various chemical processes, may act as sources for relevant prebiotic molecules.

Partial purification and characterization of phytase from Aspergillus foetidus MTCC 11682.

Phytase is a phosphatase enzyme widely used as feed additive to release inorganic phosphorus from plant phytate and enhance its uptake in monogastric animals. Although engineered fungal phytases are used most, a natural enzyme gives opportunity to understand novel properties, if any. In the current study, a novel fungal strain, Aspergillus foetidus MTCC 11682 was immobilized on poly urethane cubes and used for phytase production, purification and molecular characterization. Phytase produced by this method was partially purified by ammonium sulphate precipitation and Sephacryl S-200HR gel filtration to 23.4-fold (compared to crude extract) with recovery of 13% protein. Electrophoresis analysis revealed that phytase has molecular weight of 90.5 kDa on non-reducing and 129.6 kDa on reducing SDS-PAGE. The purified phytase exhibited a wider pH and temperature stability. Analysis of the cloned sequence showed that the gene has 1176 bp that encodes for a peptide of 391 amino acids of the core catalytic region. It was also found that phytase from A. foetidus has a sequence identity of 99% with the phytase gene of other Aspergillus species at nucleotide level and 100% at protein level in A. niger, A. awamori, A. oryzae. In silico analysis of sequence identified the presence of two consecutive and one non-consecutive intra chain disulfide bonds in the phytase. This probably contributed to the differential migration of phytase on reducing and non-reducing SDS-PAGE. There are predicted 11 O-glycosylation sites and 8 N-glycosylation sites, possibly contributed to an enhanced stability of enzyme produced by this organism. This study opened up a new horizon for exploring the novel properties of phytase for other applications.

A thirty-fold photoluminescence enhancement induced by secondary ligands in monolayer protected silver clusters.

In this paper, we demonstrate that systematic replacement of the secondary ligand PPh3 leads to an enhancement in the near-infrared (NIR) photoluminescence (PL) of [Ag29(BDT)12(PPh3)4]3-. While the replacement of PPh3 with other monophosphines enhances luminescence slightly, the replacement with diphosphines of increasing chain length leads to a drastic PL enhancement, as high as 30 times compared to the parent cluster, [Ag29(BDT)12(PPh3)4]3-. Computational modeling suggests that the emission is a ligand to metal charge transfer (LMCT) which is affected by the nature of the secondary ligand. Control experiments with systematic replacement of the secondary ligand confirm its influence on the emission. The excited state dynamics shows this emission to be phosphorescent in nature which arises from the triplet excited state. This enhanced luminescence has been used to develop a prototypical O2 sensor. Moreover, a similar enhancement was also found for [Ag51(BDT)19(PPh3)3]3-. The work presents an easy approach to the PL enhancement of Ag clusters for various applications.

Efficacy of dietary phytase supplementation on laying performance and expression of osteopontin and calbindin genes in eggshell gland.

This study was conducted to evaluate the effects of different levels of dietary phytase supplementation in the layer feed on egg production performance, egg shell quality and expression of osteopontin (OPN) and calbindin (CALB1) genes. Seventy-five White Leghorn layers at 23 weeks of age were randomly divided into 5 groups consisting of a control diet with 0.33% non-phytate phosphorus (NPP) and 4 low phosphorus (P) diets: 2 diets (T1 and T2) with 0.24% NPP + 250 FTU/kg laboratory produced phytase or commercial phytase and another 2 diets (T3 and T4) with 0.16% NPP + 500 FTU/kg laboratory produced phytase or commercial phytase with complete replacement of inorganic P. The results indicated that there were no significant differences (P > 0.05) in egg production performance and quality of egg during the first 2 months of trial. However, in next 2 months, a significant drop in egg production and feed intake was observed in birds fed diets with low P and 500 FTU/kg supplementation of laboratory produced phytase. Osteopontin gene was up-regulated whereas the CALB1 gene was down regulated in all phytase treatment groups irrespective of the source of phytase. The current data demonstrated that 250 FTU/kg supplementation of laboratory produced phytase with 50% less NPP supplementation and 500 FTU/kg supplementation of commercial phytase even without NPP in diet can maintain the egg production. The up-regulation of OPN and down regulation of CALB1 in egg shell gland in the entire phytase treated group birds irrespective of the source of enzymes is indicative of the changes in P bio-availability at this site.