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Shiv Nadar University

(SoNS) School of Natural Sciences

In proteins, the main-chain N-H⋯OC hydrogen bonds (HBs) play a crucial role in the formation of α-helices and β-sheets. Accurate analysis of such hydrogen bonds and their electrostatic interaction energies is essential for studying binding interactions and for better understanding of the energetics involved in protein folding. Here, we studied 22 high-resolution (0.87 Å to 0.48 Å) secondary protein structures (4.7 kDa to 54.5 kDa) from the RCSB PDB and performed topological analyses of 1443 N-H⋯OC HBs (750 in α-helices and 693 in β-sheets) using the multipole analysis based experimental electron densities as transferred from the ELMAM2 database. This is the first study of its kind involving by far the largest number of high-resolution protein structures and HBs from both α-helices and β-sheets. Further, based on the accurate estimation of the electrostatic interaction energies, the excellent correlations with various topological parameters have been demonstrated. The excellent correlations have also been observed between the topological parameters. Thereby, we identified the limiting values of the topological parameters and the electrostatic interaction energies to establish the presence of the true N-H⋯OC HBs in protein main-chains via quantitative and qualitative analyses of electron densities using quantum crystallographic approaches-the quantum theory of atoms in molecules (QTAIM) and the noncovalent interaction (NCI) index. © The Royal Society of Chemistry.

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Chemistry

Fulltext

CrystEngComm

Electron density based analysis of N-H⋯OC hydrogen bonds and electrostatic interaction energies in high-resolution secondary protein structures: Insights from quantum crystallographic approaches

Herein, the structural, optical, and electrical properties of Au-induced crystallization in amorphous germanium (a-Ge) thin films are presented for future solar energy material applications. The a-Ge/Au thin films on quartz substrate were prepared via the e-beam and thermal evaporation techniques, respectively. The as-prepared samples were irradiated with 100 MeV Ni7+ ions at different fluences of 1 × 1012 ions per cm2, 5 × 1012 ions per cm2, 1 × 1013 ions per cm2 and 5 × 1013 ions per cm2. The ion irradiation did not result in the crystallization of Ge; instead, an increase in ion fluence decreased the Au crystallite size, which ultimately deteriorated the Au crystallization. The ion-irradiated samples were post-annealed for 4 h at a fixed temperature of 300 °C to achieve the crystallization of Ge. The post-annealing of the ion-irradiated samples led to the crystallization of Ge, where the crystallization of Ge was better for the samples irradiated at high fluence, leading to a smaller grain size corresponding to a high grain boundary, and hence high defect sink density. The energy bandgap of crystalline Ge was determined using reflectance and transmittance spectra, which was found to be low (∼0.64 eV) at higher fluence. The field-emission scanning electron microscopy and atomic force microscopy analyses show that the surface microstructure changed for the post-annealed samples irradiated at different fluences. The role of the fractal-like surface microstructure in multiple scattering of light on the film surface is discussed. Thus, the lower values of resistivity and sheet resistance as well as good optical properties of Ge make it a promising material for future poly-Ge-based solar cell applications. © 2020 The Royal Society of Chemistry.

Physics

Crystallization of Ge in ion-irradiated amorphous-Ge/Au thin films

Coumarin and its derivatives have potential applications in sensing, laser dyes, fluorescent probes, and dye sensitized solar cells due to their unique photophysical properties. However, synthesis and studies of linear pyridine-fused-π-extended coumarins remained unexplored. Here, we synthesised two π-expanded coumarin derivatives (PC1, PC2) in which molecular backbone is linearly extended with pyridyl ring where 5,7-positions are substituted with aryl groups. Single crystal X-ray structure analysis confirmed the molecular geometry. We found in spectroscopic studies that both coumarins in solutions show fluorescence via predominant radiative decay of charge transfer (CT) state due to rotational motion associated with the molecules. In addition, detailed spectroscopic analysis of both coumarins in presence of acid and base revealed the acidochromic property in solutions. Based on the acid-base sensing property of PC1, we could show its use as solid-state acid-base vapor sensor and anti-counterfeiting agent. © 2020

Journal of Luminescence

Synthesis, optical properties, acid-base vapochromism and anti-counterfeiting of novel π-extended pyridine fused coumarins

Background: Plateletpheresis procedures are generally safe and associated with low adverse reactions. Although donor reactions and injuries are self-limited events, they may discourage donors from future platelet donations. Aim: The purpose of this study was to determine the prevalence and predictors of adverse donor reactions in plateletpheresis donors, which could serve as targets for interventions to reduce reactions. Materials and Methods: The study included 106 platelet donors over a period of 2 years. The demographic, biometric, and clinical parameters were noted. The data were analyzed for predictors of adverse donor reactions. Statistical Analysis Used: The data were analyzed using independent sample t-test to correlate donor variables such as gender. To correlate other variables such as age, weight, and whole blood processed, Chi-square test was used. Results: A total of 106 plateletpheresis donations were performed and 13.2% of vasovagal reactions were observed. The significant predictive factors for reactions were young female donors with low body weight in which more than 2.5 L volume of whole blood was processed and more than 250 ml of acid, citrate, and dextrose-A was infused and with single venous access procedures. Conclusions: The results of this study are encouraging and helpful in identifying donors at risk for developing adverse reactions during plateletpheresis so that proper and close observation during and after donation as well as timely intervention can prevent most of the unpleasant events of plateletpheresis donors. © 2020 Asian Journal of Transfusion Science | Published by Wolters Kluwer-Medknow.

Life Sciences

Asian Journal of Transfusion Science

Prevalence and predictors of adverse reactions in plateletpheresis donors with the perspective of donor safety in a tertiary care hospital of Northern India

Mature human erythrocytes contain a rich pool of microRNAs (miRNAs), which result from differentiation of the erythrocytes during the course of haematopoiesis. Recent studies have described the effect of erythrocytic miRNAs on the invasion and growth of the malaria parasite Plasmodium falciparum during the asexual blood stage of its life cycle. In this work, we have identified two erythrocytic miRNAs, miR-150-3p and miR-197-5p, that show favourable in silico hybridization with Plasmodium apicortin, a protein with putative microtubule-stabilizing properties. Co-expression of P. falciparum apicortin and these two miRNAs in a cell line model resulted in downregulation of apicortin at both the RNA and protein level. To create a disease model of erythrocytes containing miRNAs, chemically synthesized mimics of miR-150-3p and miR-197-5p were loaded into erythrocytes and subsequently used for invasion by the parasite. Growth of the parasite was hindered in miRNA-loaded erythrocytes, followed by impaired invasion; micronemal secretion was also reduced, especially in the case of miR-197-5p. Apicortin expression was found to be reduced in miRNA-loaded erythrocytes. To interpret the effect of downregulation of apicortin on parasite invasion to host erythrocytes, we investigated the secretion of the invasion-related microneme protein apical membrane antigen 1 (AMA1). AMA1 secretion was found to be reduced in miRNA-treated parasites. Overall, this study identifies apicortin as a novel target within the malaria parasite and establishes miR-197-5p as its miRNA inhibitor. This miRNA represents an unconventional nucleotide-based therapeutic and provides a new host factor-inspired strategy for the design of antimalarial molecular medicine. © 2020. Published by The Company of Biologists Ltd

DMM Disease Models and Mechanisms

Targeted repression of Plasmodium apicortin by host microRNA impairs malaria parasite growth and invasion

Development of materials for selective recovery of uranium (U) from contaminated water and sea water is necessary to solve the issues related to sources of U(VI) for nuclear energy and alleviating the environmental pollution. Phosphorous-doped Graphitic (P-Gc) material, synthesized under microwave irradiation (450 W, 40 s) has been utilized as potential adsorbent material for U removal in ppm level from contaminated water selectively at room temperature (RT). The influence of various environmental conditions (e.g. pH, contact time, ionic strength, and temperature) on U(VI) adsorption was investigated by batch method. Maximum Adsorption capacity (QM) was found 1186 mg g-1 from Langmuir fit and this could be due to high specific surface area of P-Gc (1635 m2/g) and the presence of phosphate functionalities (3.18 atomic wt\% P according to XPS) on the adsorbent surface. The results of kinetic and thermodynamic studies revealed that the adsorption was a spontaneous and exothermic chemical process and the adsorption process could be better fitted by a pseudo-second order model, suggesting a chemisorption over physisorption. The adsorption of U(VI) on P-Gc was a multilayer uptake in lower concentration range of U(VI) and monolayer in higher concentration range of U(VI). The material has been reused for five cycles with almost no change in the efficiency which is very important for the wastewater treatment. 90 \% of the adsorbed uranium was regenerated from P-Gc by simple acid treatment. Hence, P-Gc has a great promise in the quest to development of metal free adsorbent for uranium removal at RT. © 2020 Elsevier Ltd.

Journal of Environmental Chemical Engineering

Selective U(VI) removal using phosphorous-doped graphitic carbon

Efficient fluorophores with easy synthetic routes and fast responses are of great importance in clinical diagnostics. Herein, we report a new, rigid pentacyclic pyrylium fluorophore, PS-OMe, synthesised in a single step by a modified Vilsmeier-Haack reaction. Insights into the reaction mechanism facilitated a new reaction protocol for the efficient synthesis of PS-OMe which upon demethylation resulted in a "turn-on"pH sensor, PS-OH. This new fluorescent probe has been successfully used to monitor intracellular acidification at physiological pH. From the fluorescence image analysis, we were able to quantify the intracellular dynamic pH change during apoptosis. This new pH probe is a potential chemical tool for screening, drug discovery and dose determination in cancer therapy. © 2020 The Royal Society of Chemistry.

Chemical Science

A new pentacyclic pyrylium fluorescent probe that responds to pH imbalance during apoptosis

Single-component purely organic molecular crystals exhibiting negative thermal expansion (NTE) are extremely rare. Systematic studies on bromophenyl-substituted dihydro-imidazole, a novel single-component organic lightweight material, have resulted in dimorphs (centrosymmetric and noncentrosymmetric) at room temperature and two more crystal forms at low temperature (LT) upon reversible isosymmetric single-crystal-to-single-crystal transformation. While the noncentrosymmetric forms with a notable second harmonic generation activity exhibit colossal NTE and positive thermal expansion (PTE) effects with axial switching, the centrosymmetric LT phase experiences a moderate NTE but a colossal PTE. The interplay of the hydrogen bonds and weak interactions leading to the scissor jack-like molecular motion resulted in the unusual anisotropic thermal expansions over a large temperature range with record-wide (∼40 to ∼110 K) thermal hysteresis. These environmentally benign thermoresponsive materials experiencing wide thermal hysteresis, minimal volumetric thermal expansions, and reversible axial (biaxial and uniaxial) switching may find important technological applications in nonexpansive organic electronics and thermomechanical devices. © 2020 American Chemical Society

Journal of Physical Chemistry C

Unusual anisotropic thermal expansions with reversible axial switching and record-wide thermal hysteresis in single-component purely organic molecular crystals

The surface dynamics of TiO2 thin films, evolving under the implantation of 50 keV Ti ions, have been investigated. The morphological evolution, as investigated with atomic force microscopy, delineates a surface smoothening by ion implantation.The nanoscale structures at surfaces also undergo a size reduction. Scaling formalism has been applied to understand this temporal and spatial dynamics by estimating the scaling exponents (α,β and γ) via Height-height correlation function (HHCF) and power spectral density (PSD) investigations. The roughness exponent α (0.5 &lt; α &lt; 1) indicates these ion irradiated surfaces to be of self affine nature. Also, they evolve into locally smoother surfaces with increasing fluence. Negative growth exponent (β) also delineates surface smoothening. Exponent, γ, is observed to increase from ~2 at lower ion fluences to 2.5 at the highest fluence. This behavior suggests that diffusion is predominantly controlling the dynamical evolution of the ion irradiated TiO2 surfaces at the highest fluence, similar to that in the bulk case. © 2020 Elsevier B.V.

Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms

Dynamic Surface evolution and scaling studies on TiO2 thin films by Ti ion implantation

In this work, we have explored the sensing capabilities of a monolayer 1T-HfTe2 nanosheet for the environmental hazardous gases like CO, CO2, NO, NO2, NH3, and N2O, along with common environmental gases like O2, N2, H2, and H2O, using first-principles density functional theory and nonequilibrium Green's function (NEGF) based methods. Through a detailed study of structural, electronic, vibrational, and device properties, we analyzed the strength of interactions and charge transfers between the adsorbent surface and the adsorbate molecules and revealed monolayer 1T-HfTe2 to be selective to effectively sense the NO gas at very low bias. In the case of NO (NO2 and O2) adsorption, we identified a significant (moderate) amount of charge transfer with the 1T-HfTe2 nanosheet surface which leads to a considerable (moderate) change in the electronic structure of that surface, that in turn affects the other properties of the surface also. In particular, a semimetal to metal transition in the case of adsorption of NO, NO2, and O2 is noticed, with more prominance in the case of NO, which we believe to be a major reason behind the higher interaction of these gases with the 1T-HfTe2 nanosheet and a selective sensing for NO. Our device simulations to attain the I-V characteristics for the pristine 1T-HfTe2 surface and all the adsorbed ones give a direct way to measure the resistance change due to adsorption of these gases, which is a basic tool to detect gas in a "resistance sensor", and can also be measured experimentally. These calculations clearly indicate a significant (small) increase in the current when NO (NO2 and O2) was adsorbed on the nanosheet of 1T-HfTe2 and almost no increase for the rest of the examined gases. All together, by understanding the basic underlying principles, this work unlocks the potential selective NO gas sensing capability of the less explored transition metal dichalcogenide (TMD) 1T-HfTe2. Our work also reveals it to be an efficient NO sensor that works even at low voltage, leading to less power consumption, and can effectively find an application in environmental monitoring and various areas of the medical field. © 2020 American Chemical Society.