Gamma–Radiation-Assisted Synthesis of Luminescent ZnO/Ag Heterostructure Core–Shell Nanocomposites

There is increasing interest in tuning the physical properties of semiconductor nanostructures using metal nanoparticles. In this work, ZnO nanosphere covered with Ag nanoparticles were synthesized using gamma–radiation-assisted method. The amount of deposited Ag nanoparticles is controlled by changing irradiation dose in the range of 30–100 kGy in order to tune the semiconductor–metal interaction. The successful deposition of Ag on the ZnO nanoparticles is examined by analyzing the morphology, microstructure, optical, and magnetic properties of ZnO/Ag nanoparticles through field emission scanning electron (FESEM), microscopy X-ray diffraction spectra, UV-visible absorption, photoluminescence measurement, and vibrating sample magnetometer. FESEM and elemental mapping results confirmed that Ag nanoparticles have been concentrated at the surface of spherical ZnO particles. Moreover, formation of pure metallic Ag nanoparticles has been confirmed by XRD analysis. UV-visible absorption spectra of obtained ZnO/Ag showed two combined peaks, a weak peak at the shoulder around 360 nm corresponds to ZnO and a sharp absorption at 420 nm refers to spherical Ag nanoparticles. Obtained results from photoluminescence revealed that the near-band-edge emission and defect-related visible emission bands of ZnO could be enhanced dramatically at the same time by deposition of Ag nanoparticles, which was ascribed to localized surface plasmon–exciton coupling and surface plasmon scattering. Controlling the semiconductor and metal coupling effect is interesting because of its application in highly efficient optoelectronic devices and biosensor.     

Solar Selective Absorbers for High-efficiency Photothermal Conversion via Core–Shell Nanocone Structured Surface

Nanostructured surface, a promising photon management strategy, enables to enhance photon-to-heat conversion efficiency by manipulating spectral radiative properties ranging from solar spectrum (0.3–2.5 μm) to mid-infrared spectrum (2.5–20 μm). Here, a core–shell nanocone structured surface made of silica core and tungsten shell as a solar selective absorber is introduced. The photothermal conversion efficiency (PTCE) is calculated in consideration of solar spectrum absorption and mid-infrared emission. It is obvious that high solar spectrum absorption and low mid-infrared emission are beneficial for high PTCE. The influence of structural parameters on the PTCE is studied, and then the absorption enhancement mechanism is elucidated in detail. Meanwhile, the influences of incident angle, polarized state, and lattice arrangement are also presented. The calculated results exhibit that our optimized solar absorber possesses the total solar absorption of 97.3% and total thermal emission of 7.6%, resulting in a maximum PTCE of 91.4% under one sun illumination conditions at normal incidence. Moreover, our solar selective absorber is independent to the incident angle and polarization state. The excellent photothermal conversion performance with wide-angle and polarization-insensitive properties for the solar selective absorber can serve as a good candidate for various solar thermal applications including seawater desalination, steam generation, thermophotovoltaic, and photocatalysis.

     

Synthesis of (±)-Sundiversifolide Based on Lewis Acid-Mediated Claisen Rearrangement

A new and concise synthesis of (±)-sundiversifolide (1), an allelopathic bisnor-sesquiterpene lactone isolated from germinating sunflower (Helianthus annuus L.) seeds, was achieved by employing Lewis acid-mediated Claisen rearrangement as the key step.     

In Situ Polymerization of Cross-Linked Perovskite–Polymer Composites for Highly Stable and Efficient Perovskite Solar Cells

Mixed-halide perovskites have emerged as outstanding light absorbers that enable the fabrication of efficient solar cells; however, their instability hinders the commercialization of such systems. Grain-boundary (GB) defects and lattice tensile strain are critical intrinsic-instability factors in polycrystalline perovskite films. In this study, the light-induced cross-linking of acrylamide (Am) monomers with non-crystalline perovskite films is used to fabricate highly efficient and stable perovskite solar cells (PSCs). The Am monomers induce the preferred crystal orientation in the polycrystalline perovskite films, enlarge the perovskite grain size, and cross-link the perovskite grains. Additionally, the liquid properties of Am effectively releases lattice strain during perovskite-film crystallization. The cross-linked interfacial layer functions as an airtight wall that protects the perovskite film from water corrosion. Devices fabricated using the proposed strategy show an excellent power conversion efficiency (PCE) of 24.45% with an open-circuit voltage (V_OC) of 1.199 V, which, to date, is the highest V_OC reported for hybrid PSCs with electron transport layers (ETLs) comprised of TiO₂. Large-area PSC modules fabricated using the proposed strategy show a power conversion efficiency of 20.31% (with a high fill factor of 77.1%) over an active area of 33 cm², with excellent storage stability.     

A High-Performance Refractive Index Sensor Based on Hybrid Resonance Modes in a Square Nanocavity Coupled with Metal–Insulator–Metal Plasmonic Waveguide

Plasmonics - We present one of the simplest nanoscale systems for a high-performance refractive index (RI) sensor. We investigate analytically and numerically the transmission response of the...     

Direct Measurements of Erythromycin’s Effect on Protein Synthesis Kinetics in Living Bacterial Cells

Macrolide antibiotics, such as erythromycin, bind to the nascent peptide exit tunnel (NPET) of the bacterial ribosome and modulate protein synthesis depending on the nascent peptide sequence. Whereas in vitro biochemical and structural methods have been instrumental in dissecting and explaining the molecular details of macrolide-induced peptidyl-tRNA drop-off and ribosome stalling, the dynamic effects of the drugs on ongoing protein synthesis inside live bacterial cells are far less explored. In the present study, we used single-particle tracking of dye-labeled tRNAs to study the kinetics of mRNA translation in the presence of erythromycin, directly inside live Escherichia coli cells. In erythromycin-treated cells, we find that the dwells of elongator tRNA^Phe on ribosomes extend significantly, but they occur much more seldom. In contrast, the drug barely affects the ribosome binding events of the initiator tRNA^fMet. By overexpressing specific short peptides, we further find context-specific ribosome binding dynamics of tRNA^Phe, underscoring the complexity of erythromycin’s effect on protein synthesis in bacterial cells.     

Cytoprotective Effect of Estrogen on Ammonium Chloride–Treated C6-Glioma Cells

The potential cytoprotective effects of estrogen in the brain are of special interest in aging, neurodegenerative diseases, exposure to toxins, and trauma. Estrogen effects on neurons have been widely explored, but less is known about estrogen effects on glia. Glial cells are primary targets of ammonia toxicity, which arises from liver disease or failure (such as from cirrhosis in alcoholics), urea cycle disorders, or inborn errors of metabolism. We examined the ability of estrogen to protect glial cells from ammonium chloride toxicity using an in vitro model system. C6-glioma cells in later passage have many astrocytic characteristics and provided a convenient and well established model system for this work. When C6-glioma cells were exposed to 15 mM ammonium chloride, we observed major cell death (only 32% cell survival relative to control) within 72 h. Pretreatment with 17beta-estradiol (10 microM) significantly protected C6-glioma cells from ammonia toxicity (99% cell survival relative to control). In addition to enhancing the viability of C6-glioma cells against ammonia challenge, estrogen pretreatment was also found to protect mitochondrial function as assayed using the MTT reduction assay. Mitochondrial function was reduced to 39% of control levels in ammonia-challenged cultures and was mostly protected by estrogen (72% of control levels). The findings are potentially relevant for the development of therapeutic strategies to protect glial cells against ammonia toxicity resulting from hepatic failure or other causes.     

Comprehensive Study of Phase-Sensitive SPR Sensor Based on Metal–ITO Hybrid Multilayer

Plasmonics - Surface plasmon resonance (SPR) biosensor is widely used for its high precision and real-time analysis. In this paper, SPR biosensor based on the hybrid structure of metal–indium...     

Synthesis and Anticancer Activity of Novel Derivatives of α,β-Unsaturated Ketones Based on Oleanolic Acid: in Vitro and in Silico Studies against Prostate Cancer Cells

Herein, new derivatives of α,β-unsaturated ketones based on oleanolic acid ( 4 a – i ) were designed, synthesized, characterized, and tested against human prostate cancer (PC3). According to the in vitro cytotoxic study, title compounds ( 4 a – i ) showed significantly lower toxicity toward healthy cells (HUVEC) in comparison with the reference drug doxorubicin. The compounds with the lowest IC₅₀ values on PC3 cell lines were 4 b (7.785 μM), 4 c (8.869 μM), and 4 e (8.765 μM). The results of the ADME calculations showed that the drug-likeness parameters were within the defined ranges according to Lipinski's and Jorgensen's rules. For the most potent compounds 4 b , 4 c , and 4 e , a molecular docking analysis using the induced fit docking (IFD) protocol was performed against three protein targets (PARP, PI3K, and mTOR). Based on the IFD scores, compound 4 b had the highest calculated affinity for PARP1, while compound 4 c had higher affinities for mTOR and PI3K. The MM-GBSA calculations showed that the most potent compounds had high binding affinities and formed stable complexes with the protein targets. Finally, a 50 ns molecular dynamics simulation was performed to study the behavior of protein target complexes under in silico physiological conditions.     

Modelling the Efficiency of Codon–tRNA Interactions Based on Codon Usage Bias

The tRNA adaptation index (tAI) is a widely used measure of the efficiency by which a coding sequence is recognized by the intra-cellular tRNA pool. This index includes among others weights that represent wobble interactions between codons and tRNA molecules. Currently, these weights are based only on the gene expression in Saccharomyces cerevisiae. However, the efficiencies of the different codon–tRNA interactions are expected to vary among different organisms. In this study, we suggest a new approach for adjusting the tAI weights to any target model organism without the need for gene expression measurements. Our method is based on optimizing the correlation between the tAI and a measure of codon usage bias. Here, we show that in non-fungal the new tAI weights predict protein abundance significantly better than the traditional tAI weights. The unique tRNA–codon adaptation weights computed for 100 different organisms exhibit a significant correlation with evolutionary distance. The reported results demonstrate the usefulness of the new measure in future genomic studies.     

Synthesis and Antimicrobial Activity of a New Drug Based on a Retro-Analog of Cathelicidin—Polypeptide SE-33

Russian Journal of Bioorganic Chemistry - Polypeptide SE-33 (SETRPVLNRLFDKIRQVIRKFEKGIKEKSKRFF), which is a retro analog of natural antimicrobial protein cathelicidin LL-37...     

Synthesis of 3′-O-Alkyl Homologues and a Biotin Probe of Isorhamnetin and Evaluation of Cytotoxic Efficacy on Cancer Cells

Isorhamnetin is a natural flavonoid which shows a variety of biological activities such as antioxidant, anti-inflammatory and antitumor. In order to identify the cellular binding protein of isorhamnetin as potential anti-cancer target, we first synthesized 3′-O-substituted quercetin as isorhamnetin homologues and evaluated the growth inhibitory activity of these derivatives on breast, colon and prostate cancer cell lines. The preliminary results showed that the 3′-O modification did not affect the cytotoxic activity of the scaffold. Analysis of the co-crystal structure and the docking pose of isorhamnetin with reported binding protein of isorhamnetin or quercetin indicated the 3′-O-substitution groups located outside of the binding pocket, which is in accordance with activity of 3′-O derivatives. Then a biotin conjugate of isorhamnetin with a tetraethylene glycol (PEG)₄ linker at the 3′ position was synthesized and the resulting probe retained the anti-proliferative activity on cancer cell lines, while the cellular fluorescence analysis showed the distribution of probe inside the cells which indicated the probe had limited cell permeability. Finally, pull down assay both in situ inside cells and in the cell lysates indicated the isorhamnetin biotin probe was capable of protein labeling in cell lysates. These findings provide the isorhamnetin 3′-O-biotin probe as a tool to reveal the target proteins of isorhamnetin.     

Zombie Cells,Composite Cells of Fungal–Human Keratinocytes of Plantar Hyperkeratosis-Like Lesions

Mycopathologia - Foot hyperkeratosis is common. They often coincide with fungal infections, are difficult to cure and relapse rates are high. In this case study, longstanding and intractable...     

Synthesis of (–)-Muricatacin

The synthesis of (–)-muricatacin starting from 1-bromododecane and 2-pentyn-l-ol is described. 2-Pentadecyn-1-ol (4), which was prepared from 1-bromododecane (2) and 2-pentyn-1-ol (3), was converted to epoxy alcohol 6 through a two-step reaction sequence, 6 being successively submitted to tosylation, iodination, chain extension with tert-butyl lithioacetate, and acid-catalyzed cyclization to give (–)-muricatacin (1a). Recrystallization afforded optically pure 1a.     

First principles investigation of oxygen adsorptions on hydrogen–terminated ZnO graphene-like nanosheets

The structures of ZnO graphene–like nanosheets (ZnOGLNS), i.e., ZnO aromatic–like (AL–ZnONS), naphthalene–like (NLL–ZnONS), pyrene–like (PRL–ZnONS), coronene–like (CNL–ZnONS) and circumcoronene–like (CCL–ZnONS) and their oxygen adsorptions were obtained using the B3LYP/LanL2DZ method. Adsorption energies of O₂ on AL–ZnONS, NLL–ZnONS, PRL–ZnONS, CNL–ZnONS and CCL–ZnONS are reported. The bond strengths of the most inner Zn–O bonds of ZnOGLNSs are in order: CCL–ZnONS > CNL–ZnONS > PRL–ZnONS. It was found that chemisorptions of O₂ occur on the hydride atoms of zinc–hydride in the ZnOGLNSs. Physisorptions of O₂ only occurring over the plane of ZnOGLNS were found. All the ZnOGLNSs are oxygen sensitive materials and would be developed to be oxygen sensor based on electrical conductivity.     

Synthesis of citrate–ciprofloxacin conjugates

Two regioisomeric citrate-functionalized ciprofloxacin conjugates have been synthesized and their antimicrobial activities against a panel of clinically-relevant bacteria have been determined. Cellular uptake mechanisms were investigated using wild-type and ompF deletion strains of Escherichia coli K-12.     

Synthesis of DNA-(3′)-PNA Chimeras with Conformationally Restricted Linkers Based on 4-Hydroxyproline

Abstract

The synthesis and evaluation of DNA-(3′)-PNA chimeras containing rigid linkers based on (R/S)-4-hydroxy-D/L-proline are described. It is shown that installment of the trans-L-linker using the tetrabutylammonium salt of (R)-4-(4,4′-dimethoxytrityloxy)-N-(thymin-1-yl)acetyl-L-proline (2) leads to a DNA-(3′)-PNA chimera which hybridizes efficiently with complementary RNA.     

Influence of Levosimendan Postconditioning on Apoptosis of Rat Lung Cells in a Model of Ischemia–Reperfusion Injury

Objective

To ascertain if levosimendan postconditioning can alleviate lung ischemia–reperfusion injury (LIRI) in rats.

Method

One hundred rats were divided into five groups: Sham (sham), ischemia–reperfusion group (I/R group), ischemic postconditioning (IPO group), levosimendan postconditioning (Levo group) and combination postconditioning group of levosimendan and 5-Hydroxydecanoic acid (Levo+5-HD group). The apoptotic index (AI) of lung tissue cells was determined using the terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay. Expression of active cysteine aspartate specific protease-3 ( active caspase-3), Bcl-2 and Bax in lung tissue was determined by immunohistochemical staining. The morphopathology of lung tissue was observed using light and electron microscopy.

Results

AI values and expression of active caspase-3, Bcl-2 and Bax of lung tissue in I/R and Levo+5-HD groups were significantly higher than those in the sham group ( P<0.05). AI values and expression of active caspase-3 and Bax were significantly lower, whereas that of Bcl-2 was higher significantly in the Levo group, compared with I/R and Levo+5-HD groups (P<0.05). Significant differences were not observed in comparisons between I/R and Levo+5-HD groups as well as IPO and Levo groups.

Conclusion

LIRI can be alleviated by levosimendan, which simulates an IPO protective function. A postulated lung-protective mechanism of action could involve opening of mitochondrial adenosine triphosphate-sensitive potassium channels, relieving Ca2+ overload, upregulation of expression of Bcl-2, and downregulation of expression of active caspase-3 and Bax.