Search

• Inextensional vibrations are studied through strain gradient elasticity. • First work on inextensional modes of spherical shell using strain gradient theory. • Formulae for inextensional vibration frequencies are derived. We study inextensional vibrations of the spherical shell using strain gradient elasticity theory under Kirchhoff-Love hypotheses. For admissibility of the inextensional deformations the shell is punctured by making a tiny hole. The shell is assumed to be made of linearly elastic, homogeneous, and isotropic material. The closed form expression for the frequencies of inextensional modes of vibration of spherical caps of various polar angles and that of nearly complete spherical shell are derived using Rayleigh's method. Towards this, the displacement and velocity fields are obtained by setting the membrane strains to zero. Further, to facilitate the existence of inextensional vibrations, boundaries are assumed to be traction free. The frequencies are computed for the positive and negative signs in the strain gradient term of the constitutive law. The computed frequencies, employing negative sign are found to be higher than those computed using classical elasticity theory. The opposite effect is seen when the frequencies are computed with the positive sign. Further, the frequencies are found to saturate when the positive sign is used in the constitutive law. Parametric studies viz. variation in frequencies with the circumferential wavenumbers for different values of length scale parameter, variation in frequencies with circumferential wavenumbers for different values of polar angles and a given length scale parameter, variation of frequency with increasing polar angle for a given circumferential wavenumber, variation of saturation wavenumber with increasing polar angle, and increasing length scale parameter are carried out. The frequencies of nearly a spherical shell with increasing circumferential wavenumber are also computed. [ABSTRACT FROM AUTHOR]

Photocatalysis has emerged as a promising approach for generating solar chemical and organic transformations under the solar light spectrum, employing polymer photocatalysts. In this study, our aim is to achieve the regeneration of NADH and fixation of nitroarene compounds, which hold significant importance in various fields such as pharmaceuticals, biology, and chemistry. The development of an in-situ nature-inspired artificial photosynthetic pathway represents a challenging task, as it involves harnessing solar energy for efficient solar chemical production and organic transformation. In this work, we have successfully synthesized a novel artificial photosynthetic polymer, named TFc photocatalyst, through the Friedel-Crafts alkylation reaction between triptycene (T) and a ferrocene motif (Fc). The TF C photocatalyst is a promising material with excellent optical properties, an appropriate band gap, and the ability to facilitate the regeneration of NADH and the fixation of nitroarene compounds through photocatalysis. These characteristics are necessary for several applications, including organic synthesis and environmental remediation. Our research provides a significant step forward in establishing a reliable pathway for the regeneration and fixation of solar chemicals and organic compounds under the solar light spectrum. Bio-inspired In-Situ Synthesis of Polymer Photocatalyst for Selective Enzymatic 1,4-NADH Regeneration and Nitroarene Fixation. [Display omitted] • Polymer Photocatalyst for Selective Enzymatic Regeneration and Nitroarene Fixation. • Photocatalyst exhibits exceptional optical properties. • Photocatalyst exhibits exceptional photocatalytic performance and selectivity. [ABSTRACT FROM AUTHOR]

Indeed, the development of ecologically benign molecular fabrication methods for highly efficient graphene quantum dots-based photocatalysts is of great significant. Graphene quantum dots-based photocatalysts have promising applications in various field, including environmental remediation, energy conversion, and splitting of water. However, ensuring resource reusability and minimizing the environmental impact are crucial considerations in the development. From this perspective, attention has also been paid to the creation of easy to make solar light harvesting graphene quantum dots-based photocatalysts for synthesising pharmaceuticals and functional imines compounds. Imines are excellent significant building blocks in pharmaceutical chemistry and excellent examples of these valuable compounds' synthetic intermediates, and the environmentally friendly oxidative synthesis of imines from amines. Therefore, herein, we designed a facile and efficient condensation route to synthesize the Nen-GQDs@PH photocatalyst. This route involves coupling of 2,4-dinitrophenylhydrazine (PH) with nitrogen-enriched graphene quantum dots (Nen-GQDs). The Nen-GQDs@PH as photocatalyst functions in a highly selective and efficient manner, leading to high amines conversion efficiency to imines (95%). Our results highlight a novel and environmentally safe approach for generating highly selective imines from various types of amines, setting a new benchmark in the current research field. [Display omitted] • Synthesis of Nitrogen-enriched graphene quantum dots (Nen-GQDs) coupled with 2,4-dinitrophenylhydrazine (PH). • Detailed characterizations of Nen-GQDs@PH photocatalyst. • Utilization of Nen-GQDs@PH as an efficient and effective photocatalyst. • Propose a plausible mechanism for the conversion of benzyl amines to imines using Nen-GQDs@PH as photocatalyst. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Physicochemical properties of graphene oxide modified with cobalt metalated aminoporphyrin. • Photosynthetic conversion of formic acid from carbon-dioxide. • Significantly effective for NADH photoregeneration. • Photoelectrochemical measurement showed photocurrent properties. • Energy applications. Abstract An increasingly level of one of the important greenhouse gas, CO 2 , in the atmosphere from anthropogenic human activities has several adverse consequences and thus, chemical transformation of carbon dioxide into useful, renewable and environmentally friendly products is becoming an important research problem. In the present investigation, we have developed photocatalyst of graphene oxide modified with cobalt metallated aminoporphyrin (GO-Co-ATPP) for conversion of CO 2 to formic acid under visible light. The efficiency of nanohybrid photosynthetic conversion of formic acid from carbon-dioxide is 96.49 μmol for 2 h. We have used XRD, SEM, HR-TEM, AFM, thermogravimetric analysis, BET measurement to establish the structural and physical properties along with infrared spectroscopy and Raman spectroscopy for chemical properties of GO-Co-ATPP. The photocatalyst was significantly effective for NADH photoregeneration with cumulative 48.53% over time and photoelectrochemical measurement showed photocurrent properties. These results strongly suggest that the GO-Co-ATPP photocatalyst materials may open new vistas in conversion of CO 2 into useful and environmentally friendly products as well as energy applications. [ABSTRACT FROM AUTHOR]

The consumption of carbon dioxide (CO 2) for direct solar fuel productions and synthesis of fine solar chemicals are gaining leading significance due to the shortage of fossil-fuel and global warming worldwide. Therefore, herein, we report the synthesis and development of solar light harvesting bamboo - shape magnesium tetraphenyl porphyrin based framework (Mg-TPPBF) photocatalyst. The development of Mg-TPPBF photocatalyst-biocatalyst bonded system as a solar light harvesting photocatalyst functions in a extremely efficient manner, increasing to high regeneration of NADH (73.9%), followed by its utilization in exclusive amount of formic acid (HCOOH) production (197.2 μmol) from CO 2. The Mg-TPPBF photocatalyst also enables in consecutive C-S/C-N bonds formation with high yield (~96–99%) and selectivity (~97–99%) under solar light with excellent reusability. The current research work highlights the enlargement and application of Mg-TPPBF photocatalyst for direct solar fuel production from CO 2 and fine solar chemical synthesis. • Atmospheric CO 2 level enhancement cause serious environmental problems. • Mg-TPPBF−F ate DH coupled artificial photosynthetic system reduces CO 2 into HCOOH. • Mg-TPPBF photocatalyst catalyzed C-S/C-N bonds formation under solar light. • The photocatalytic products are useful in agrochemical & pharmacological actions. [ABSTRACT FROM AUTHOR]

[Display omitted] • The structural and electronic property explains that the cation Li+ attraction towards ether oxygen of PEO based on Hard-Soft Acid Base Principle. • Reduction in crystalline nature of PEO is observed after addition of plasticiser PEG. • The reduce in the forbidden gap with the addition of PEG in polymer-metal complex justifies the increase in the ionic conductivity. Quantum chemistry-based codes and methods provide valuable computational tools to study the atomic and molecular structure of any system. This paper provides insights into the electronic and structural properties of polyethylene oxide (PEO) and polyethylene glycol (PEG) based solid polymer electrolyte incorporated with lithium iodide as ion-conducting species using first principle method. PEO shows insulator characteristics with a broad bandgap of 5.2 eV which decreased significantly to 3.19 eV in PEO-PEG-LiI. The wide forbidden energy band gap of PEO-PEG-LiI concludes that conductivity in polymer electrolytes is predominantly ionic rather than electronic. The presence of hydrogen bonding between PEG and PEO shows their amazing compatibility. Hirschfield population analysis (HPA) quantify the interactions involved within the structure and explains the interaction of Li-ion with ether group of PEO. Overlapping of wavefunctions of C, O and H atoms in polymers proves the existence of partial ionic and partial covalent bonding among them. [ABSTRACT FROM AUTHOR]

Abstract: The endogenous cation in peroxidases may contribute to the type of heme coordination. Here a series of ferric and ferrous derivatives of wild-type Leishmania major peroxidase (LmP) and of engineered K+ site mutants of LmP, lacking potassium cation binding site, has been examined by electronic absorption spectroscopy at 25°C. Using UV–visible spectrophotometry, we show that the removal of K+ binding site causes substantial changes in spin states of both the ferric and ferrous forms. The spectral changes are interpreted to be, most likely, due to the formation of a bis-histidine coordination structure in both the ferric and ferrous oxidation states at neutral pH 7.0. Stopped flow spectrophotometric techniques revealed that characteristics of Compound I were not observed in the K+ site double mutants in the presence of H2O2. Similarly electron donor oxidation rate was two orders less for the K+ site double mutants compared to the wild type. These data show that K+ functions in preserving the protein structure in the heme surroundings as well as the spin state of the heme iron, in favor of the enzymatically active form of LmP. [Copyright &y& Elsevier]

Abstract: Heme peroxidases are a class of multifunctional redox-active proteins found in all organisms. We recently cloned, expressed, and characterized an ascorbate peroxidase from Leishmania major (LmAPX) that was capable of detoxifying hydrogen peroxide. Localization studies using green fluorescent protein fusions revealed that LmAPX was localized within the mitochondria by its N-terminal signal sequence. Subcellular fractionation analysis of the cell homogenate by the Percoll density-gradient method and subsequent Western blot analysis with anti-LmAPX antibody further confirmed the mitochondrial localization of mature LmAPX. Submitochondrial fractionation analysis showed that the mature enzyme (∼3.6 kDa shorter than the theoretical value of the whole gene) was present in the intermembrane space side of the inner membrane. Moreover, expression of the LmAPX gene was increased by treatment with exogenous H2O2, indicating that LmAPX was induced by oxidative stress. To investigate the biological role of LmAPX we generated Leishmania cells overexpressing LmAPX in the mitochondria. Flow-cytometric analysis, thin-layer chromatography, and IC50 measurements suggested that overexpression of LmAPX caused depletion of the mitochondrial ROS burden and conferred a protection against mitochondrial cardiolipin oxidation and increased tolerance to H2O2. These results suggest that the single-copy LmAPX gene plays a protective role against oxidative damage. [Copyright &y& Elsevier]

Abstract: We report here that the Leishmania major ascorbate peroxidase (LmAPX), having similarity with plant ascorbate peroxidase, catalyzes the oxidation of suboptimal concentration of ascorbate to monodehydroascorbate (MDA) at physiological pH in the presence of added H2O2 with concurrent evolution of O2. This pseudocatalatic degradation of H2O2 to O2 is solely dependent on ascorbate and is blocked by a spin trap, α-phenyl-n-tert-butyl nitrone (PBN), indicating the involvement of free radical species in the reaction process. LmAPX thus appears to catalyze ascorbate oxidation by its peroxidase activity, first generating MDA and H2O with subsequent regeneration of ascorbate by the reduction of MDA with H2O2 evolving O2 through the intermediate formation of O2 −. Interestingly, both peroxidase and ascorbate-dependent pseudocatalatic activity of LmAPX are reversibly inhibited by SCN− in a concentration dependent manner. Spectral studies indicate that ascorbate cannot reduce LmAPX compound II to the native enzyme in presence of SCN−. Further kinetic studies indicate that SCN− itself is not oxidized by LmAPX but inhibits both ascorbate and guaiacol oxidation, which suggests that SCN− blocks initial peroxidase activity with ascorbate rather than subsequent nonenzymatic pseudocatalatic degradation of H2O2 to O2. Binding studies by optical difference spectroscopy indicate that SCN− binds LmAPX (Kd=100±10 mM) near the heme edge. Thus, unlike mammalian peroxidases, SCN− acts as an inhibitor for Leishmania peroxidase to block ascorbate oxidation and subsequent pseudocatalase activity. [Copyright &y& Elsevier]

Numerous reports have shown that mitochondrial dysfunctions play a major role in apoptosis of Leishmania parasites, but the endoplasmic reticulum (ER) stress-induced apoptosis in Leishmania remains largely unknown. In this study, we investigate ER stress-induced apoptotic pathways in Leishmania major using tunicamycin as an ER stress inducer. ER stress activates the expression of ER-localized chaperone protein BIP/GRP78 (binding protein/identical to the 78-kDa glucose-regulated protein) with concomitant generation of intracellular reactive oxygen species. Upon exposure to ER stress, the elevation of cytosolic Ca2+ level is observed due to release of Ca2+ from internal stores. Increase in cytosolic Ca2+ causes mitochondrial membrane potential depolarization and ATP loss as ablation of Ca2+ by blocking voltage-gated cation channels with verapamil preserves mitochondrial membrane potential and cellular ATP content. Furthermore, ER stress-induced reactive oxygen species (ROS)-dependent release of cytochrome c and endonuclease G from mitochondria to cytosol and subsequent translocation of endonuclease G to nucleus are observed. Inhibition of caspase-like proteases with the caspase inhibitor benzyloxycarbonyl-VAD-fluoromethyl ketone or metacaspase inhibitor antipain does not prevent nuclear DNA fragmentation and phosphatidylserine exposure. Conversely, significant protection in tunicamycin-induced DNA degradation and phosphatidylserme exposure was achieved by either pretreatment of antioxidants (N-acetyl-L-cysteine, GSH, and L-cysteine), chemical chaperone (4-phenylbutyric acid), or addition of Ca2+ chelator (1,2-bis(2-aminophenoxy)ethane-N,JV,N,N-tetraacetic acidacetoxymethyl ester). Taken together, these data strongly demonstrate that ER stress-induced apoptosis in L. major is dependent on ROS and Ca2+-induced mitochondrial toxicity but independent of caspase-like proteases. [ABSTRACT FROM AUTHOR]

Abstract: Oral administration of saponins isolated from Albizia lebbeck bark at the dose level of 50mg/kg/b.w. per day for 60 days to male rats brought about a significant decrease in the weights of testes, epididymides, seminal vesicle and ventral prostate. The production of round spermatid was reduced by 73.04% in Albizia lebbeck treated rats. The population of preleptotene spermatocytes and spermatogonia were reduced by 65.07% and 47.48% and secondary spermatocytes by 73.41%, respectively. Cross sectional surface area of Sertoli cells as well as the cell counts were found to be depleted significantly. Leydig cell nuclear area and number of mature Leydig cells were decreased by 57.47% and 54.42%, respectively. Sperm motility as well as sperm density were reduced significantly. Albizia lebbeck reduced the fertility of male rats by 100%. There were no significant changes in RBC and WBC count, haemoglobin, haematocrit and glucose in the blood and cholesterol, protein, triglyceride and phospholipid in the serum. The protein, glycogen and cholesterol contents of the testes, fructose in the seminal vesicle and protein in epididymides were significantly decreased. Histoarchitecture of the testes showed vacuolization at primary spermatocytes stage. Highly reduced seminiferous tubular diameter and increased intertubular space were also observed when compared to controls. [Copyright &y& Elsevier]

Abstract: Herein, for the first time, CuAlGaO4 is demonstrated as an efficient visible-light-active (band-gap of 1.87eV, λ ≥420nm) photocatalyst for solar H2 production. The CuAlGaO4 prepared by solid-state method is capable of producing 3214μmol of H2 per hour from H2S photodecomposition under visible-light irradiation with quantum yield of 10.8% at 550nm. Loading with 1wt.% NiO enhances the rate of H2 generation of the photocatalyst to 3616μmolh−1 with quantum yield of 12.7% at 550nm. The CuAlGaO4 exhibits a spinel structure with particle size varying from a few nanometers to a few micrometers. The regenerated catalysts validate the stability and the reusability. [Copyright &y& Elsevier]