Photoelectrochemical performance of bilayered Fe–TiO<Subscript>2</Subscript>/Zn–Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> thin films for solar generation of hydrogen

A visible-light sensitive bilayered photoanode of Fe–TiO₂/Zn–Fe₂O₃ has been developed by spray pyrolytically depositing Zn–Fe₂O₃ layers onto predeposited Fe–TiO₂ thin film on ITO substrate. Fe–TiO₂/Zn–Fe₂O₃ photoelectrodes were characterized by XRD, Raman, AFM, UV-vis absorption spectroscopy. Photoelectrochemical properties of bilayered Fe–TiO₂/Zn–Fe₂O₃ photoelectrode were studied by Mott–Schottky curves and I–V characteristics. Bilayered Fe–TiO₂/Zn–Fe₂O₃ photoelectrode was observed to possess much higher separation efficiency of photogenerated charge carriers and could generate nine times better photocurrent density than pure Fe–TiO₂. Solar to hydrogen conversion efficiency exhibited by this electrode was 0.77%.     

Isolation of template effects that control the structure and function of nonspherical, biotemplated Pd nanomaterials

Advances in nanotechnology have indicated that the passivant and the inorganic surface play a pivotal role in controlling the structure/function relationship of materials. Beyond standard materials-based methods, bioligands have recently demonstrated the production of unique nanomaterial morphologies for application under ambient conditions for multiple activities, such as catalysis and biosensing. We have recently demonstrated that a biotemplate technique could be employed to produce spherical and linear Pd nanostructures in water using a self-assembling peptide framework. The materials possessed high catalytic reactivity that was controlled by the three-dimensional structure of the composite materials. To investigate the effect of the peptide template on the reactivity of Pd nanostructures, an in depth analysis of the catalytic activity of Pd nanostructures fabricated via truncated templates is presented. The new templates were designed from portions of the original framework, which demonstrated unique synthetic and functionality control. Two different reactions, Stille C-C coupling and 4-nitrophenol reduction, were employed to ascertain the effect of template structure on the reactivity of synthesized Pd nanomaterials via changes in reagent diffusion through the bioscaffold. The results indicate that the peptide framework plays an important role and could be used to tune and optimize the functionality of the final composite materials for the target application.     

Poly(L-Lysine)-pyranine-3 coacervate mediated nanoparticle-assembly: fabrication of dynamic pH-responsive containers

Counter-ion condensation of Poly(L-Lysine) in the presence of pyranine-3 generates spherical coacervates, which then template the assembly of silica nanoparticles to form microcapsule structures that dynamically control the optical ratiometric sensing of both the change in pH and release of the probe molecule.     

Electron beam irradiation induced changes in the dielectric and electro-optical properties of a room temperature nematic display material 4-(trans-4′-n-hexylcyclohexyl) isothiocyanatobenzoate (6CHBT)

Dielectric and electro-optical studies of a pure and electron beam irradiated liquid crystalline compound 4-(trans-4′-n-hexylcyclohexyl) isothiocyanatobenzoate have been carried out. Dielectric anisotropy, relaxation frequency, activation energy and distribution parameter of an observed non-collective mode corresponding to the molecular rotation about the short axes have been determined as a function of temperature and irradiation dose whereas threshold and switching voltages, splay elastic constant are determined as a function of irradiation dose. The relaxation frequencies initially decrease up to an irradiation dose of 40 kGy but thereafter increase due to irradiation. The activation energies are increased up to irradiation dose of 40 kGy but around 60 kGy dose of irradiation, we found decrease in the activation energy. Electro-optical measurements show the lowering of the threshold voltage with sufficient improvement in the steepness of the transmission voltage curves due to irradiation. The observed changes in the dielectric and electro-optical properties are related with the cis–trans isomerization due to electron beam irradiation.     

Point mutations in SARS-CoV-2 variants induce long-range dynamical perturbations in neutralizing antibodies

Monoclonal antibodies are emerging as a viable treatment for the coronavirus disease 19 (COVID-19). However, newly evolved variants of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can reduce the efficacy of currently available antibodies and can diminish vaccine-induced immunity. Here, we demonstrate that the microscopic dynamics of neutralizing monoclonal antibodies can be profoundly modified by the mutations present in the spike proteins of the SARS-COV-2 variants currently circulating in the world population. The dynamical perturbations within the antibody structure, which alter the thermodynamics of antigen recognition, are diverse and can depend both on the nature of the antibody and on the spatial location of the spike mutation. The correlation between the motion of the antibody and that of the spike receptor binding domain (RBD) can also be changed, modulating binding affinity. Using protein-graph-connectivity networks, we delineated the mutant-induced modifications in the information-flow along allosteric pathway throughout the antibody. Changes in the collective dynamics were spatially distributed both locally and across long-range distances within the antibody. On the receptor side, we identified an anchor-like structural element that prevents the detachment of the antibodies; individual mutations there can significantly affect the antibody binding propensity. Our study provides insight into how virus neutralization by monoclonal antibodies can be impacted by local mutations in the epitope via a change in dynamics. This realization adds a new layer of sophistication to the efforts for rational design of monoclonal antibodies against new variants of SARS-CoV2, taking the allostery in the antibody into consideration.

Mutations in the new variants of SARS-CoV-2 spike protein modulates the dynamics of the neutralizing antibodies. Capturing such modulations from MD simulations and graph network model identifies the role of mutations in facilitating immune evasion.     

Geochemical characterization of miocene core sediments from Shahbazpur gas-wells (Bangladesh) in terms of elemental abundances by instrumental neutron activation analysis

Journal of Radioanalytical and Nuclear Chemistry - Geochemical characterization of Shahbazpur structure (Bengal Foredeep) in terms of elemental abundances obtained from INAA are presented by...     

Pyranocarbazoles from Murraya koenigii (L.) Spreng. as antimicrobial agents

The bioassay guided fractionation of methanolic extract of Murraya koenigii (L.) Spreng. leaves resulted in the isolation of seven pyranocarbazoles. These were evaluated against four bacterial strains and ten Candida sp. including two matched pair of fluconazole sensitive/resistant clinical isolates. Out of seven, three i.e. Koenine (mk279), Koenigine (mk309) and Mahanine (mk347) exhibited significant antibacterial activity MIC90 3.12–12.5 μg/mL against bacterial strains Streptococcus aureus and Klebsiella pneumonia compared with standard drug Kanamycin MIC90 12.5 μg/mL. However, only mk309 was found active against variety of Candida species MIC90 12.5–100 μg/mL. It was observed that hydroxylation at C-6 and C-7 positions in the studied pyranocarbazoles activate the bioactivity. Simultaneously, decrease in Log P value compares with ?H and ?O?CH3 substituted derivatives. The study is focused on selective antifungal and antibacterial activity of pyranocarbazoles on bacterial strains S. aureus, K. pneumonia and variety of Candida species with structure activity relationship observations.     

Redox‐Active Peptide‐Functionalized Quinquethiophene‐Based Electrochromic π‐Gel

An electrochromic system based on a self‐assembled dipeptide‐appended redox‐active quinquethiophene π‐gel is reported. The designed peptide‐quinquethiophene consists of a symmetric bolaamphiphile that has two segments: a redox‐active π‐conjugated quinquethiophene core for electrochromism, and peptide motif for the involvement of molecular self‐assembly. Investigations reveal that self‐assembly and electrochromic properties of the π‐gel are strongly dependent on the relative orientation of peptidic and quinquethiophene scaffolds in the self‐assembly system. The colors of the π‐gel film are very stable with fast and controlled switching speed at room temperature.