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Shiv Nadar University

(SoNS) School of Natural Sciences

In the presence of eosin Y, a visible light-induced one-step procedure (isolated yield of ≥75%) for thiolation of substituted 1,4-naphthoquinones using various aromatic and aliphatic thiols at room temperature is described herein. The rate-determining step of the reaction is thiyl radical generation, and the radical was characterized by high-resolution mass spectrometry. Cost effectiveness, operational simplicity, a short reaction time, high atom economy, and a very good yield make this photoredox-mediated process a useful alternative to the transition metal (e.g., Cu, Ag, and Pd)-catalyzed coupling reaction of quinones with thiols or disulfides. © 2022 American Chemical Society. All rights reserved.

World University root node

Chemistry

Journal of Organic Chemistry

Visible Light-Mediated Thiolation of Substituted 1,4-Naphthoquinones Using Eosin y as a Photoredox Catalyst

Let GL3(Zn) denote the set of 3 × 3 invertible matrices with entries from Zn, the ring of integers modulo n. We study the distribution of a matrix function called the permanent, restricting its domain to GL3(Zn). Given x ∈ Z, we count the number of elements in the set G3(n, x) = {M ∈ GL3(Zn) | perm(M) ≡ x (mod n)}. © 2022, Colgate University. All rights reserved.

Mathematics

Integers

PERMANENTS OF 3 × 3 INVERTIBLE MATRICES MODULO N

Castor oil (CO) and cocoa butter (CB) were studied as potential hydrophobic and plasticizer additives for pectin biopolymer films. The optimum concentration of CO and CB additives and drying temperature were determined by using a 23 (two-level, three-factor) statistical factorial design of experiments. The CO and CB integrated pectin films displayed remarkably lower moisture and oxygen transmission rates relative to the control pectin films. Furthermore, the hydrophobicity, ductility (elongation at break) and flexibility (low elastic modulus) of the CO and CB added films are significantly higher than that of the control pectin films. The modified films retained 90% of their weight at a temperature of 200 °C, indicating their excellent thermal stability. A very low glass transition temperature of 2 ± 2 °C and a melting point of ~ 150 °C of the films designates their stability under processing and storage conditions. Scanning electron microscopy analysis confirmed the formation of homogeneous films without any micro-cracks or agglomerations. Detailed statistical analysis shows that the optimal conditions for producing improved pectin films: the concentration of CO (15% w/w of pectin) and CB (10% w/w of pectin) and film drying temperature (T = 35–52 °C). A coating of film forming solution comprising optimum amounts of pectin, CO and CB was able to delay the ripening of a banana by 4 days and of capsicum by 15 days at atmospheric conditions. © 2022, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.

Physics

Mechanical Engineering

(SoE) School of Engineering

Journal of Polymers and the Environment

Castor Oil and Cocoa Butter to Improve the Moisture Barrier and Tensile Properties of Pectin Films

The β phase of tungsten has attracted great interest for spintronic applications due to its higher spin Hall angle compared to other elemental solids and large spin-orbit torque, but the stability of this phase is yet to be well understood as many different results are there in the literature mainly based on the film thickness, temperature, and overall growth conditions. The growth of films by sputter deposition has emerged as a promising technique to achieve β-W owing to its compatibility with current spintronic technology. We demonstrate here the efficient ability of dc magnetron sputtering to grow stable β-W films up to a thickness of ∼180 nm at room temperature by varying a set of deposition parameters like pressure, power, and deposition time and discuss the various underlying mechanisms. From these results, the optimized set of deposition parameters for growing β-W films is given. A clear understanding of the influence of oxygen in the atomic structure of β-W is obtained by varying the thickness of the films. This is confirmed from the ab initio molecular dynamics (MD) simulations, where the atomic structure is influenced by the oxygen doping concentration. A stable polycrystalline β phase can be achieved by controlled doping of oxygen. Additionally, a phase transformation from α to β with the doping of oxygen is also evident by MD simulations. © 2022 Author(s).

Journal of Applied Physics

Growth-dependent structural ordering and stability in β-tungsten films for spintronic applications

Cytochrome P450 peroxygenases use hydrogen peroxide to hydroxylate long-chain fatty acids by bypassing the use of O2 and a redox partner. Among the peroxygenases, P450OleT uniquely performs decarboxylation of fatty acids and production of terminal olefins. This route taken by P450OleT is intriguing, and its importance is augmented by the practical importance of olefin production. As such, this mechanistic choice merits elucidation. To address this puzzle, we use hybrid QM/MM calculations and MD simulations for the OleT enzyme as well as for the structurally analogous enzyme, P450BSβ. The study of P450OleT reveals that the protonated His85 in the wild-type P450OleT plays a crucial role in steering decarboxylation activity by stabilizing the corresponding hydroxoiron(IV) intermediate (Cpd II). In contrast, for P450BSβ in which Q85 replaces H85, the respective Cpd II species is unstable and it reacts readily with the substrate radical by rebound, producing hydroxylation products. As shown, this single-site difference creates in P450OleT a local electric field (LEF), which is significantly higher than that in P450BSβ. In turn, these LEF differences are responsible for the different stabilities of the respective Cpd II/radical intermediates and hence for different functions of the two enzymes. P450BSβ uses the common rebound mechanism and leads to hydroxylation, whereas P450OleT proceeds via decarboxylation and generates terminal olefins. Olefin production projects the power of a single residue to alter the LEF and the enzyme’s function. © 2022 American Chemical Society

Journal of Chemical Information and Modeling

Local Electric Fields Dictate Function: The Different Product Selectivities Observed for Fatty Acid Oxidation by Two Deceptively Very Similar P450-Peroxygenases OleT and BSβ

Ni(ii)-tetradentate amido-quinoline complexes effectively catalysed C-H chlorination of a series of hydrocarbons in the presence of NaOCl and acetic acid. The bond dissociation energy of the C(sp3)-H bond of the substrates varies from 99.3 kcal mol−1 (cyclohexane) to 87 kcal mol−1 (ethyl benzene). Exclusively chlorinated products (TON: 220 for cyclohexane) were obtained without any hydroxylated products, thus mimicking the activity of the halogenase enzyme. © 2022 The Royal Society of Chemistry

Chemical Communications

C-H bond chlorination using nickel(ii) complexes of tetradentate amido-quinoline ligands

The lack of a convenient method for the iterative generation of diverse full-length viral variants has impeded the study of directed evolution in RNA viruses. By integrating a full RNA genome error-prone PCR and reverse genetics, random genome-wide substitution mutagenesis can be induced. We have developed a method using this technique to synthesize diverse libraries to identify viral mutants with phenotypes of interest. This method, called full-length mutant RNA synthesis (FL-MRS), offers the following advantages: (i) the ability to create a large library via a highly efficient one-step error-prone PCR; (ii) the ability to create groups of libraries with varying levels of genetic diversity by manipulating the fidelity of DNA polymerase; (iii) the creation of a full-length PCR product that can directly serve as a template for mutant RNA synthesis; and (iv) the ability to create RNA that can be delivered into host cells as a non-selected input pool to screen for viral mutants of the desired phenotype. We have found, using a reverse genetics approach, that FL-MRS is a reliable tool to study viral-directed evolution at all stages in the life cycle of the hepatitis C virus, JFH1 isolate. This technique appears to be an invaluable tool to employ directed evolution to understand adaptation, replication, and the role of viral genes in pathogenesis and antiviral resistance in positive-sense RNA viruses. © 2022, Journal of Visualized Experiments. All rights reserved.

Life Sciences

Journal of Visualized Experiments

Reverse Genetics to Engineer Positive-sense RNA Virus Variants

In order to survive and establish infection, the Plasmodium parasite employs various strategies to evade the host immune response. The var genes family, a repertoire of 60 genes, expresses parasite-specific protein PfEMP1, a variable surface antigen, on the membrane of infected erythrocytes, and by continuously switching the variants of PfEMP1, help the parasite to avoid detection and destruction by the host immune system during the intra-erythrocytic developmental cycle. Although chromatin modifications are recognised to be a prominent phenomenon in regulation of mono-allelic expression of these var genes, the precise histone codes and molecular players and mechanisms guiding these modifications have yet to be unravelled in depth. In this study, we have functionally characterised RUVBL proteins of Plasmodium falciparum and shown that PfMYST (an essential lysine acetyl transferase) and PfRUVBL protein complex occupy the TARE region and var gene promoter in the ring stage of the parasite. Further, we have demonstrated that the PfMYST/PfRUVBL complex interacts with core histones, H3 and H4. Overall the findings of this study add further information by identifying the potential role of epigenetic regulators, PfMYST and PfRUVBL, in the regulation of monoallelic expression of var genes in the malaria parasite. © The Author(s) 2022.

Pathogens and Disease

Plasmodium falciparum PfRUVBL proteins bind at the TARE region and var gene promoter located in the subtelomeric region

Removal of heavy metals (Cd and Cr) from industrial wastewater by adsorption onto a series of Ca substituted nickel zinc nanoferrites (CaxNi0.4Zn0.6-xFe2O4 (x = 0.1, 0.2, 0.3, 0.4, 0.5 and 0.6)) (CNZNFs) was studied in detail. The effect of calcium doping and contact time over adsorption of cadmium and chromium ions was investigated and maximum uptake of Cd (98.25%) and Cr (51%) ions were marked by prepared nanoadsorbents. Structural studies confirmed the formation of spinel structured nanoparticles with crystallite size ranging from 24 to 38 nm while porosity was observed to vary from 52% to 58% with calcium concentration. Pseudo second order (PSO) kinetic model for adsorption of both heavy metals (cadmium and chromium) was observed to be better fitted with adsorption data. Maximum adsorption efficiencies for Cd (128.20 mg/g) and Cr (23.54 mg/g) were found by the data fit of Langmuir isotherm model. Additionally, the adsorption data was found to obey Langmuir isotherm model for both heavy metals due to higher values of correlation coefficients (R2 = 0.94131 for cadmium and 0.91091 for chromium) than Freundlich isotherm model (R2 = 0.5865 for cadmium and 0.4599 for chromium). © 2022 Elsevier Ltd and Techna Group S.r.l.