Synthetic reactions catalyzed by immobilized lipase from oilseed rape (Brassica napus L.)

Lipase from rape (Brassica napus L., immobilized onto celite, catalyzes esterification and transesterification reactions in hexane. The activity of the lipase is stimulated up to 35 fold by the addition of water (1.3% w/v). The activity of the lipase in hydrolysis is about 8 times higher than in the esterification reactions in hexane. Interesteri-fication reactions between mono- and diacylglycerols and transesterification reactions of mono- and diacylglycerols with alcohols were also catalyzed at relatively high rates but transesterification/esterification of these acylglycerols with fatty acids was comparatively slow. In transesterification reactions, triacylglycerols reacted rather slowly.     

Determination of ten rare-earth elements and yttrium in silicate rocks by ICP-AES without separation and preconcentration

Lanthanum, cerium, neodymium, samarium, europium, gadolinium, dysprosium, erbium, ytterbium, lutetium and yttrium have been determined in 8 international rock standards by inductively coupled plasma atomic emission spectrometry (ICP-AES) without prior ion-exchange separation and preconcentration. The results for La, Ce, Nd, Eu, Dy, Yb and Y were in good agreement with the reported values, whereas those for Sm, Gd, Er and Lu were less accurate. However, the results for Sm, Gd, Er and Lu can also be used for studies of petrogenesis.     

A facile and versatile protocol for the one-pot PhI(OAc)2 mediated divergent synthesis of quinazolines from 2-aminobenzylamine

In this present work iodobenzenediacetate (PIDA) has been found to be the key reagent in absence or presence of catalytic amount of molecular iodine (I₂)/zinc chloride (ZnCl₂) to construct quinazoline scaffold from 2-aminobenzylamine and a variety of easily available aldehydes, aryl and aliphatic amines, aliphatic and aryl alcohols and nitriles. This protocol provides mild and robust conditions along with great versatility to synthesize 2-substituted quinazolines from diverse starting materials in good to excellent yields. The developed protocol is also well applicable to reactants containing ease to oxidation prone functional groups.     

Oxidation studies of Indian reduced activation ferritic martensitic steel

The paper reports the oxidation behaviour of Indian variety of reduced activation ferritic martensitic steel (RAFMS) proposed to be used as a first wall material in test blanket module in ITER and future fusion reactors. Oxidation of first wall can occur in case of a catastrophic leak in the vacuum vessel of fusion reactor. The oxidation of Indian RAFMS was done at 450–650 °C. Long-term oxidation for 25, 50 and 100 h was studied at 550 °C. A mass gain/unit area vs time was plotted and oxidation kinetics determined. The cross section SEM of the oxidised RAFMS was done. The SEM micrographs showed two distinct layers of oxides that have formed with total thickness of around 10 µm. Glancing-angle XRD showed that the top layer is essentially a mixture of magnetite and haematite. A strong enrichment of Cr is visible in a narrow band below the top layer near the scale/alloy interface. It was found that formation of this Cr-rich spinel mid-layer ensures the short-term and long-term oxidation resistance of IN-RAFMS in case of any accidental leak in fusion reactor conditions.     

Co-operative intra-protein structural response due to protein–protein complexation revealed through thermodynamic quantification: study of MDM2-p53 binding

The p53 protein activation protects the organism from propagation of cells with damaged DNA having oncogenic mutations. In normal cells, activity of p53 is controlled by interaction with MDM2. The well understood p53-MDM2 interaction facilitates design of ligands that could potentially disrupt or prevent the complexation owing to its emergence as an important objective for cancer therapy. However, thermodynamic quantification of the p53-peptide induced structural changes of the MDM2-protein remains an area to be explored. This study attempts to understand the conformational free energy and entropy costs due to this complex formation from the histograms of dihedral angles generated from molecular dynamics simulations. Residue-specific quantification illustrates that, hydrophobic residues of the protein contribute maximum to the conformational thermodynamic changes. Thermodynamic quantification of structural changes of the protein unfold the fact that, p53 binding provides a source of inter-element cooperativity among the protein secondary structural elements, where the highest affected structural elements (α2 and α4) found at the binding site of the protein affects faraway structural elements (β1 and Loop1) of the protein. The communication perhaps involves water mediated hydrogen bonded network formation. Further, we infer that in inhibitory F19A mutation of P53, though Phe19 is important in the recognition process, it has less prominent contribution in the stability of the complex. Collectively, this study provides vivid microscopic understanding of the interaction within the protein complex along with exploring mutation sites, which will contribute further to engineer the protein function and binding affinity.     

Synthesis and characterization of some novel cyanonitrosyl complexes of chromium(I) with Mannich bases,aromatic aldehyde oximes and syn-phenyl-2-pyridylketoxime

Some new low-spin hexacoordinated cyanonitrosyl complexes of Cr¹ of the type [Cr(NO)(CN)₂(L)₂(H₂)], where L is an aromatic aldehyde oxime or Mannich base, have been prepared by the interaction or K₃[Cr(NO)(CN)₅]· H₂O with L in aqueous AcOH, and characterized by a range of physico-chemical techniques, I.r. data suggest that all the oxime derivatives and Mannich bases act as monodentate ligands by coordinating through the aromatic nitrogen. TMC 2564     

Self-assembled metallasupramolecular cages towards light harvesting systems for oxidative cyclization

Designing artificial light harvesting systems with the ability to utilize the output energy for fruitful application in aqueous medium is an intriguing topic for the development of clean and sustainable energy. We report here facile synthesis of three prismatic molecular cages as imminent supramolecular optoelectronic materials via two-component coordination-driven self-assembly of a new tetra-imidazole donor (L) in combination with 180°/120° di-platinum(ii) acceptors. Self-assembly of 180° trans-Pt(ii) acceptors A1 and A2 with L leads to the formation of cages Pt₄L₂(1a) and Pt₈L₂(2a) respectively, while 120°-Pt(ii) acceptor A3 with L gives the Pt₈L₂(3a) metallacage. PF₆⁻ analogues (1b, 2b and 3b) of the metallacages possess a high molar extinction coefficient and large Stokes shift. 1b–3b are weakly emissive in dilute solution but showed aggregation induced emission (AIE) in a water/MeCN mixture as well as in the solid state. AIE active 2b and 3b in aqueous (90% water/MeCN mixture) medium act as donors for fabricating artificial light harvesting systems via Förster resonance energy transfer (FRET) with organic dye rhodamine-B (RhB) with high energy efficiency and good antenna effect. The metallacages 2b and 3b represent an interesting platform to fabricate new generation supramolecular aqueous light harvesting systems with high antenna effect. Finally, the harvested energy of the LHSs (2b + RhB) and (3b + RhB) was utilized successfully for efficient visible light induced photo-oxidative cross coupling cyclization of N,N-dimethylaniline (4) with a series of N-alkyl/aryl maleimides (5) in aqueous acetonitrile with dramatic enhancement in yields compared to the reactions with RhB or cages alone.

Synthesis of Pt(ii) based metallacages as aggregation induced emissive supramolecular architectures for fabricating artificial light harvesting systems for cross coupling cyclization under visible light is achieved.     

Leveraging an enzyme/artificial substrate system to enhance cellular persulfides and mitigate neuroinflammation

Persulfides and polysulfides, collectively known as the sulfane sulfur pool along with hydrogen sulfide (H₂S), play a central role in cellular physiology and disease. Exogenously enhancing these species in cells is an emerging therapeutic paradigm for mitigating oxidative stress and inflammation that are associated with several diseases. In this study, we present a unique approach of using the cell''s own enzyme machinery coupled with an array of artificial substrates to enhance the cellular sulfane sulfur pool. We report the synthesis and validation of artificial/unnatural substrates specific for 3-mercaptopyruvate sulfurtransferase (3-MST), an important enzyme that contributes to sulfur trafficking in cells. We demonstrate that these artificial substrates generate persulfides in vitro as well as mediate sulfur transfer to low molecular weight thiols and to cysteine-containing proteins. A nearly 100-fold difference in the rates of H₂S production for the various substrates is observed supporting the tunability of persulfide generation by the 3-MST enzyme/artificial substrate system. Next, we show that the substrate 1a permeates cells and is selectively turned over by 3-MST to generate 3-MST-persulfide, which protects against reactive oxygen species-induced lethality. Lastly, in a mouse model, 1a is found to significantly mitigate neuroinflammation in the brain tissue. Together, the approach that we have developed allows for the on-demand generation of persulfides in vitro and in vivo using a range of shelf-stable, artificial substrates of 3-MST, while opening up possibilities of harnessing these molecules for therapeutic applications.

A persulfide/hydrogen sulfide generation strategy through artificial substrates for 3-mercaptopyruvate sulfurtransferase (3-MST) is reported, which enhances cellular persulfides, attenuates reactive oxygen species (ROS), and alleviates inflammation.     

Atomistic De-novo Inhibitor Generation-Guided Drug Repurposing for SARS-CoV-2 Spike Protein with Free-Energy Validation by Well-Tempered Metadynamics

Computational drug design is increasingly becoming important with new and unforeseen diseases like COVID-19. In this study, we present a new computational de novo drug design and repurposing method and applied it to find plausible drug candidates for the receptor binding domain (RBD) of SARS-CoV-2 (COVID-19). Our study comprises three steps: atom-by-atom generation of new molecules around a receptor, structural similarity mapping to existing approved and investigational drugs, and validation of their binding strengths to the viral spike proteins based on rigorous all-atom, explicit-water well-tempered metadynamics free energy calculations. By choosing the receptor binding domain of the viral spike protein, we showed that some of our new molecules and some of the repurposable drugs have stronger binding to RBD than hACE2. To validate our approach, we also calculated the free energy of hACE2 and RBD, and found it to be in an excellent agreement with experiments. These pool of drugs will allow strategic repurposing against COVID-19 for a particular prevailing conditions.