Bipy Research Articles

Effect of HEDTA on the Adsorption of 2,2 Bipyridyl and 3-Mercaptobenzothiazole and Electroless Cu Deposition Rate

Surface-enhanced Raman spectroscopy (SERS) and chronoamperometry were utilized to evaluate the electroless deposition of Cu in hydroxyethylethylelenediaminetriacetic acid (HEDTA)- and tartrate-based baths containing 2,2′-bipyridyl (BP) and 2-mercaptobenzothiazole (MBT). The Cu deposition rate was shown to be faster in tartrate baths, with rates at 0.08 μm min−1 without MBT or BP but decreased to near zero with concentrations approaching 6 μM of either MBT or BP. HEDTA baths displayed a slower rate of 0.04 μm min−1 without MBT or BP. However, the addition of MBT increased the rate up to 4-fold, while BP concentration did not affect the deposition rate. SERS data showed that HEDTA adsorbs to the surface while tartrate does not. Kinetic Langmuir isotherm model fits showed a decrease in MBT and BP adsorption rate in the presence of HEDTA and showed a decrease in HEDTA adsorption upon MBT injection while BP injection did not affect the HEDTA adsorption. Competition between the complexing and the stabilizing agent is a key factor for the rate of electroless Cu deposition.

Engineered Amine-Functionalized Metal-Organic Framework to Fabricate a Composite for Next-Generation Asymmetric Supercapacitors with Ultrahigh Performance: Modulating the Energy Storage Barrier.

The present work summarizes the fabrication of an amine-functionalized cadmium-based metal-organic framework (MOF), {[Cd(AT)(BP)]·4DMF}n or Cd_AT-BP, by adopting a simple solvothermal approach using 2-aminoterephthalic acid (AT) as the main linker, while 4,4'-bipyridyl (BP) as an auxiliary linker. The structure of Cd_AT-BP was validated by the single-crystal X-ray diffraction technique that revealed the formation of an overall three-dimensional network with BP acting as a bridge between the 2D sheets of the MOF. The robust framework of Cd_AT-BP decorated with a free amine functional group was utilized for energy storage application. The electrochemical measurements of Cd_AT-BP revealed a maximum areal capacitance of 9.8 mF/cm2 at a scan rate of 5 mV/s. Further, to enhance the practical utility of Cd_AT-BP in energy storage devices, two composites of Cd_AT-BP with reduced graphene oxide (rGO) and multiwalled carbon nanotubes (CNTs), viz., Cd_AT-BP/rGO and Cd_AT-BP/CNT, were prepared by adopting a facile ultrasonication approach. The synthesized Cd_AT-BP/rGO and Cd_AT-BP/CNT composites displayed an impressive areal capacitance of 117 and 37 mF/cm2 (58.5 and 17.5 F/g) at a scan rate of 5 mV/s, respectively, and a capacitance retention of up to 118 and 100% after 5000 cycles at a constant current density of 5 mA/cm2. The highest energy density of about 4.23 mW h/cm2 (2.12 W h/kg) at a current density of 1 mA/cm2 was shown by Cd_AT-BP/rGO among all the three materials attributable to the layered structure of rGO, providing a larger surface area accessible for ion adsorption. Enticed by the remarkable outcomes exhibited by Cd_AT-BP/rGO, we fabricated a two-electrode asymmetric supercapacitor (ASC) device. The developed ASC device revealed energy and power densities of 26.7 mW h/cm2 (13.4 W h/kg) and 3760 mW/cm2 (1880 W/kg), respectively, with a galvanostatic charge-discharge stability of up to 10,000 cycles. The findings identify Cd_AT-BP/rGO as a potential contender for future-generation supercapacitors.

Both hemoglobin and hemin cause damage to retinal pigment epithelium through the iron ion accumulation

Subretinal hemorrhages result in poor vision and visual field defects. During hemorrhage, several potentially toxic substances are released from iron-based hemoglobin and hemin, inducing cellular damage, the detailed mechanisms of which remain unknown. We examined the effects of excess intracellular iron on retinal pigment epithelial (RPE) cells. A Fe2+ probe, SiRhoNox-1 was used to investigate Fe2+ accumulation after treatment with hemoglobin or hemin in the human RPE cell line ARPE-19. We also evaluated the production of reactive oxygen species (ROS) and lipid peroxidation. Furthermore, the protective effect of-an iron chelator, 2,2′-bipyridyl (BP), and ferrostatin-1 (Fer-1) on the cell damage, was evaluated. Fe2+ accumulation increased in the hemoglobin- or hemin-treated groups, as well as intracellular ROS production and lipid peroxidation. In contrast, BP treatment suppressed RPE cell death, ROS production, and lipid peroxidation. Pretreatment with Fer-1 ameliorated cell death in a concentration-dependent manner and suppressed ROS production and lipid peroxidation. Taken together, these findings indicate that hemoglobin and hemin, as well as subretinal hemorrhage, may induce RPE cell damage and visual dysfunction via intracellular iron accumulation.

Role of bipyridyl in enhancing ferrate oxidation toward micropollutants

Enhancing Fe(VI) oxidation ability by generating high-valent iron-oxo species (Fe(IV)/Fe(V)) has attracted continuous interest. This work for the first time reports the efficient activation of Fe(VI) by a well-known aza-aromatic chelating agent 2,2′-bipyridyl (BPY) for micropollutant degradation. The presence of BPY increased the degradation constants of six model compounds (i.e., sulfamethoxazole (SMX), diclofenac (DCF), atenolol (ATL), flumequine (FLU), 4-chlorophenol (4-CP), carbamazepine (CBZ)) with Fe(VI) by 2 – 6 folds compared to those by Fe(VI) alone at pH 8.0. Lines of evidence indicated the dominant role of Fe(IV)/Fe(V) intermediates. Density functional theory calculations suggested that the binding of Fe(III) to one or two BPY molecules initiated the oxidation of Fe(III) to Fe(IV) by Fe(VI), while Fe(VI) was reduced to Fe(V). The increased exposures of Fe(IV)/Fe(V) were experimentally verified by the pre-generated Fe(III) complex with BPY and using methyl phenyl sulfoxide as the probe compound. The presence of chloride and bicarbonate slightly affected model compound degradation by Fe(VI) in the presence of BPY, while a negative effect of humic acid was obtained under the same conditions. This work demonstrates the potential of N-donor heterocyclic ligand to activate Fe(VI) for micropollutant degradation, which is instructive for the Fe(VI)-based oxidation processes.

Effect of Ni on Electroless Cu Plating Rates in the Presence of 2,2′-Bipyridyl and 2-Mercaptobenzothiazole

Electrochemical measurements and Surface Enhanced Raman Spectroscopy (SERS) are used to evaluate the effect of Ni addition on the rate of Cu electroless deposition in the presence of 2,2′-bipyridyl (BP) and 2-mercaptobenzothiazole (MBT). Ni addition is found to increase the rate of electroless Cu deposition in the presence of BP but had no effect on the rate in the presence of MBT. In situ SERS obtained at the potential of electroless deposition shows that BP is destabilized from the Cu surface in the presence of Ni, likely due to the increased positive charge present with Ni-incorporated Cu. The BP deficient surface exhibits a higher electroless deposition rate relative to a surface with substantial BP. In contrast, SERS shows that Ni addition does not alter MBT adsorption to Cu, due to the increased affinity of MBT to the electrode surface relative to BP.

Cobalt Hydrogen-Bonded Organic Framework as a Visible Light-Driven Photocatalyst for CO2 Cycloaddition Reaction.

A novel cobalt hydrogen-bonded organic framework (Co-HOF, C24H14CoN4O8) was synthesized from a mixed linker, that is, 2,5-pyridinedicarboxylic acid (PDC) and 2,2'-bipyridyl (BPY) linkers and cobalt ion through a simple, one-pot, low-cost, and scalable solvothermal method. The Co-HOF was fully characterized using several analytical and spectroscopic techniques including single-crystal X-ray diffraction, diffuse reflectance spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, energy-dispersive X-ray, and X-ray photoelectron spectroscopy. The Co-HOF exhibits high thermal and chemical stabilities compared to previously reported HOF materials. Moreover, Co-HOF shows excellent photocatalytic activity under visible light irradiation due to its narrow band gap of 2.05 eV. The cycloaddition reaction of CO2 to variable epoxides was investigated to evaluate the photocatalytic performance of Co-HOF under visible light radiation and was found to produce the corresponding cyclic carbonates in yields up to 99.9%.

Macrocyclic Peptides Closed by a Thioether-Bipyridyl Unit That Grants Cell Membrane Permeability.

Membrane permeability is an important factor that determines the virtue of peptides targeting intracellular molecules. By introducing a membrane penetration motif, some peptides exhibit better membrane permeabilities. Previous choices for such motifs have usually been polycationic sequences, but their protease vulnerabilities and modest endosome escapability remain challenging. Here, we report a strategy for macrocyclization of peptides closed by a hydrophobic bipyridyl (BPy) unit, which grants an improvement of their membrane permeability and proteolytic stability compared with the conventional polycationic peptides. We chemically prepared model macrocyclic peptides closed by a thioether-BPy unit and determined their cell membrane permeability, giving 200 nM CP50 (an indicative value of membrane permeability), which is 40-fold better than that of the ordinary thioether macrocycle consisting of the same sequence composition. To discover potent target binders consisting of the BPy unit, we reprogrammed the initiator with chloromethyl-BPy (ClMeBPy) for the peptide library synthesis with a downstream Cys residue(s) and executed RaPID (Random nonstandard Peptide Integrated Discovery) against the bromodomains of BRD4. One of the obtained sequences exhibited a single-digit nanomolar dissociation constant against BRD4 in vitro and showed approximately 2-fold and 10-fold better membrane permeability than positive controls, R9 and Tat peptides, respectively. Moreover, we observed an intracellular activity of the BPy macrocycle tagged with a proteasome target peptide motif (RRRG), resulting in modest but detectable degradation of BRD4. The present demonstration indicates that the combination of the RaPID system with an appropriate hydrophobic unit, such as BPy, would provide a potential approach for devising cell penetrating macrocycles targeting various intracellular proteins.

Phototoxic Potential of Different DNA Intercalators for Skin Cancer Therapy: In Vitro Screening.

Photodynamic therapy is a minimally invasive procedure used in the treatment of several diseases, including some types of cancer. It is based on photosensitizer molecules, which, in the presence of oxygen and light, lead to the formation of reactive oxygen species (ROS) and consequent cell death. The selection of the photosensitizer molecule is important for the therapy efficiency; therefore, many molecules such as dyes, natural products and metallic complexes have been investigated regarding their photosensitizing potential. In this work, the phototoxic potential of the DNA-intercalating molecules-the dyes methylene blue (MB), acridine orange (AO) and gentian violet (GV); the natural products curcumin (CUR), quercetin (QT) and epigallocatechin gallate (EGCG); and the chelating compounds neocuproine (NEO), 1,10-phenanthroline (PHE) and 2,2'-bipyridyl (BIPY)-were analyzed. The cytotoxicity of these chemicals was tested in vitro in non-cancer keratinocytes (HaCaT) and squamous cell carcinoma (MET1) cell lines. A phototoxicity assay and the detection of intracellular ROS were performed in MET1 cells. Results revealed that the IC50 values of the dyes and curcumin in MET1 cells were lower than 30 µM, while the values for the natural products QT and EGCG and the chelating agents BIPY and PHE were higher than 100 µM. The IC50 of MB and AO was greatly affected by irradiation when submitted to 640 nm and 457 nm light sources, respectively. ROS detection was more evident for cells treated with AO at low concentrations. In studies with the melanoma cell line WM983b, cells were more resistant to MB and AO and presented slightly higher IC50 values, in line with the results of the phototoxicity assays. This study reveals that many molecules can act as photosensitizers, but the effect depends on the cell line and the concentration of the chemical. Finally, significant photosensitizing activity of acridine orange at low concentrations and moderate light doses was demonstrated.

Cocrystals of Nitrofurantoin: How Coformers Can Modify Its Solubility and Permeability Across Intestinal Cell Monolayers

Solubility and permeability of nitrofurantoin (NITRO) were compared with those of its cocrystals containing isoniazid (ISO), bipyridyl (BIP), or phenanthroline (PHE) as coformers, and their parent mixtures. NITRO dissolution profiles were evaluated via HPLC; we resorted to molecular dynamics (MD) simulations to rationalize the experimental data on the basis of nitrofurantoin–coformers and nitrofurantoin–water intermolecular interactions. Permeation studies were performed by using an in vitro model of the small intestine based on IEC-6 cells. The NITRO water solubility was reduced by its mixture with PHE and BIP but not with ISO. Cocrystallization with BIP induced a slight increase of NITRO solubility; cocrystallization with PHE induced its solubility decrease, even if lower than the physical mixture. The solubility changes were attributed to NITRO solvation shell alterations (MD simulations). Cocrystallization with ISO allowed an increase of the NITRO solubility in the first 30 min of the dissolution pattern. Permeation measurements showed that the NITRO–PHE mixture was detrimental for the monolayer integrity, whereas no alterations were induced by the cocrystal. No effects on NITRO permeability and monolayer integrity were observed either for NITRO–ISO or for NITRO–BIP mixtures. The NITRO–ISO cocrystal increased the NITRO permeability across the monolayer without reducing its integrity.

Inhibition of LpxC Increases the Activity of Iron Chelators and Gallium Nitrate in Multidrug-Resistant Acinetobacter baumannii.

Infections caused by multidrug-resistant Acinetobacter baumannii would benefit from the development of novel treatment approaches. Compounds that interfere with bacterial iron metabolism, such as iron chelators and gallium nitrate, have previously been shown to have antimicrobial activity against A. baumannii. In this study, we characterize the effect of LpxC inhibitors on the antimicrobial activity of previously characterized iron chelators, 2,2′-bipyridyl (BIP) and deferiprone (DFP), and gallium nitrate (Ga(NO3)3) against A. baumannii reference strains and multidrug-resistant clinical isolates. The LpxC inhibitor LpxC-2 was synergistic with BIP for 30% of strains tested (FICI values: 0.38–1.02), whereas inhibition with LpxC-4 was synergistic with BIP for 60% of strains tested (FICI values: 0.09–0.75). In time–kill assays, combinations of BIP with both LpxC inhibitors demonstrated synergistic activity, with a more than 3 log10 reduction in bacterial counts compared to BIP alone. LpxC-2 was synergistic with Ga(NO3)3 for 50% of strains tested (FICI values: 0.27–1.0), whereas LpxC-4 was synergistic with Ga(NO3)3 for all strains tested (FICI values: 0.08–≤0.50). In time–kill assays, combinations of Ga(NO3)3 with LpxC-2 and LpxC-4 decreased the growth of both strains compared to each compound separately; however, only the combination with LpxC-4 met the defined criteria for synergy. These results identify a novel synergy between two antimicrobial classes against A. baumannii strains.

Labile iron affects pharmacological ascorbate-induced toxicity in osteosarcoma cell lines

Vitamin C and iron are both important nutrients for humans and involved in several physiological processes. The biological activities of vitamin C and iron are based on their abilities to accept or donate electrons. Although vitamin C is well known as an excellent electron donor in physiological conditions, it also has pro-oxidant properties, especially with catalytic metal iron. Cancer cells have a higher iron requirement than normal cells, which allows pharmacological ascorbate to kill cancer cells selectively. In this study, we demonstrated that the levels of H2O2 in cells were significantly raised after treated with pharmacological ascorbate, and intracellular labile iron could increase pharmacological ascorbate-mediated oxidative stress by Fenton reaction. Catalytic metal iron plays opposite roles in and outside cells. Intracellular excess labile iron improved ascorbate-induced toxicity, while the excess labile iron in the medium abolished ascorbate-induced toxicity. Fe3+ and Fe2+ have the same effect on ascorbate-induced toxicity, but Fe3+ chelator deferoxamine (DFO) has a profound inhibition effect than Fe2+ chelator 2,2′-bipyridyl (BIP) on ascorbate-induced toxicity. The influence of intracellular labile iron and ascorbate on the ferritin expression may cause selective sensitivity in osteosarcoma cell lines on pharmacological ascorbate. High iron requirement of many cancer cells facilitates pharmacological ascorbate on cancer treatment. In addition, increasing iron content in tumour tissue may be effective strategies to improve the effects of pharmacological ascorbate.

Luminescent properties of newly synthesized thioxanthone-polypyridyl derivatives and their metal-organic complexes

Thioxanthones (TXs) are not only important photoinitiators for free radical polymerization but also efficient light-harvesting units for organic light emitting diodes. Here, we reported synthesis and photophysical properties of new TXs with 2,2′-bipyridyl (BPy) and 2,2':6′,2″-terpyridyl (TPy) substituents, TXOBPy and TXOTPy, as well as those of their complexes with some transition metal ion (Zn2+, Fe2+, Ni2+, Eu3+ and Tb3+) solution in diverse solvents and solid powders. Absorption spectra revealed mainly two groups of bands at approximately 250–290 and 366 nm, attributed to the π–π* and n–π* electron transfer of the TXs. A broad luminescent emission was recorded and centered at approximately 422 nm for these TXs and their metal complexes, its relative intensity was solvent and concentration dependent. Further, it was observed that this emission band red shifted to approximately 470 nm in their solid powders. For the TXs and their Zn/Fe/Ni-complexes in the methanol solutions, the quantum efficiency (QE) of TX rings was about 0.04–0.11, and the fluorescent lifetime (τ) was about 0.5–1.2 ns. On the other hand, for the Fe and Ln-complexes, the QE of TX rings was below 0.01, which was attributed to the reason that the excited energy of the TX rings was quenched by ligand-Fe2+ charge transfer or by transferring the energy to the central Ln3+ (Eu3+ and Tb3+) ions. Thus, the Ln-TXOBPy and Ln-TXOTPy complexes gave off strong and sharp Eu3+/Tb3+ emissions at the wavelengths between 480 and 750 nm. The fluorescent emission lifetime of the central Ln3+ ions was about 0.3–0.6 ms. Thus, we can suggest that the TXOBPy and TXOTPy photoinitiators can act as potential candidates for the development of efficient emitters with tunable light emissions and luminescent sensors.

Catalytic conversion of a lignin model compound to value-added products using Cu/TEMPO-catalyzed aerobic oxidation

Catalytic oxidation of vanillyl alcohol (VAL), a lignin model compound, to vanillin (VN), a value-added product, is typically implemented using transition metals with non-recyclable H2O2 as an oxidant. In this study, an alternative oxidation process is proposed for VAL oxidation to VN by using CuI as a catalyst, 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) as a co-catalyst and ambient air as an oxygen source. This Cu/TEMPO has been validated as a highly effective and chemoselective catalytic process for oxidation of alcohols to corresponding aldehydes. CuI coordinated with 2,2′-bipyridyl (BIPY)/1-methylimidazole (MIM) could mediate the cyclic oxidative transformation between TEMPOH and TEMPO, which then oxidizes the OH group of VAL to an aldehyde group, leading to the formation of VN. In addition, the effect of temperature seems as the most influencing factor for VAL oxidation. In particular, the conversion of VAL can reach 99% with a high selectivity of 93% at 90 °C, and the corresponding production is the record-high value of 89%, tremendously higher than the reported values in the literature. These features indicate that Cu/TEMPO-catalyzed aerobic oxidation is indeed a promising, highly selective, and efficient means for valorization of VAL, the lignin model compound, to the target product, VN.

Three Component Controls in Pillared Metal-Organic Frameworks for Catalytic Carbon Dioxide Fixation

Three components of pillared metal-organic frameworks (MOFs, three components = metal ion, carboxylic acid ligand, and N-chelating ligand) were controlled for CO2 cycloaddition catalysts to synthesize organic cyclic carbonates. Among the divalent metals, Zn2+ showed the best catalytic activity, and in DABCO (1,4-diazabicyclo[2.2.2]octane)-based MOFs, hydroxy-functionalized DMOF-OH was the most efficient MOF for CO2 cycloaddition. For the BPY (4,4’-bipyridyl)-type MOFs, all five prepared BMOFs (BPY MOFs) showed similar and good conversions for CO2 cycloaddition. Finally, this pillared MOF could be recycled up to three times without activity and crystallinity loss.

Interfacial self-assembly of bipyridyl-functionalized nanoSiO2-BPy@Ln(β-diketone)n composites and their luminescent properties

Interfacial self-assembly provides an effective route to design and construct various metal-organic hybrid and composite materials with interesting optical and electroactive properties. Here, we reported the interfacial self-assembly of luminescent nano-composites through the coordination reaction of lanthanide salts of Ln(CF3SO3)3 (Ln = Eu and Tb) with the 2,2′-bipyridyl (BPy)-functionalized silica nano-linkers (nanoSiO2-BPy) and several β-diketone ligands. The assembling processes and the nano-materials as-prepared were characterized by using thermogravimetry, infrared, UV–vis absorption and X-ray photoelectron spectroscopy, as well as field emission transmission electron microscopy (FE-TEM). The luminescent properties from both nanoSiO2-BPy linkers and lanthanide nano-composites were investigated in the solutions and solid powders, which revealed not only the broad emissions of nanoSiO2-BPy linkers between 400 and 520 nm, but also the sharp emissions between 480 and 750 nm, designated to the 4f–4f electron transitions of 5D4 → 7Fn (n = 3,4,5,6) and 5D0 → 7Fn (n = 0,1,2,3,4) of the Tb3+ and Eu3+ ions, respectively. The relative emission intensity of the Ln3+ ions in the nano-composites has been found to be closely dependent on the compositions of the nano-composites, structure of the β-diketone ligands, and the excited wavelengths. Finally, the energy transfer process in the nano-composites was discussed.

Competition between five different chelates to capture of uranyl ion: Synthesis, spectroscopic, thermal, surface and biological investigations

The uranium ion in various chemical forms is one of the most valuable metals that exists in seawater. To recognize the uranyl ion (UO22+) is a longstanding goal for the purposes of environmental remediation, metallurgical extraction, and water purification from seawater. Uranium complexes of the composition UO2L(NO3)2, where L is 2-[(5-o-chlorophenylazo-2-hydroxybenzylidin)amino]-phenol Schiff base (SB), N-(1-naphthyl)ethylenediamine (ND), N,N,N′,N′-tetramethylethylenediamine (TD), α,α′-bipyridyl (BP), or hexamethylenediamine (HD) were synthesized and characterized by several physicochemical techniques. This study investigated the microstructure properties of these complexes using XRD and SEM techniques. Furthermore, the antimicrobial activity of the complexes was assessed against two types of bacterium and fungus species. The complexes decompose endothermically in a single-to-fourth steps to give a solid powder of UO2 or UCx (where x=1 or 2) as the residual product through indefinite intermediates. All of the uranyl complexes seem to possess a hexagonal bipyramidal geometry surrounding the uranium atom.

Abstract 13202: Cellular Iron Regulates Mitochondrial Dynamics Through the RNA-Binding Protein Tristetraprolin (TTP)

Background: Iron is a critical molecule for normal cellular and physiologic processes including mitochondrial energy production. Previous work in our lab has established the RNA-binding protein TTP as a protein whose expression is induced by iron deprivation. TTP functions by binding to AU-rich elements in the 3’UTR of mRNAs and promotes their degradation. Many of the targets of TTP encode metabolically active proteins that function in pathways requiring iron. Recently, we have identified Mitofusin 1 (MFN1), a critical component of the mitochondrial fusion machinery, as a novel target of TTP. Published reports have shown MFN1/2 double knockout mice develop spontaneous cardiomyopathy. Conversely, under conditions of ROS induced cellular stress, MFN1 knockout in cardiomyocytes has been associated with protection from cell death. We hypothesize that the level of MFN1 closely matches the metabolic demands of the cell and, therefore, induction of TTP by low iron reduces the level of MFN1 to fragment the mitochondria and limit the cell’s ability to proliferate during conditions of iron insufficiency. Results: Twenty-four hours of iron chelation using either desferoxamine (DFO) or 2-2, bipyridyl (BPD) induced TTP expression at both the mRNA and protein levels in a dose-dependent manner. In silico analysis of the MFN1 3’UTR revealed four conserved AU-rich elements. Basal levels of MFN1 were increased in TTP KO cells indicating TTP actively targets MFN1 mRNA. Additionally, iron chelation decreased MFN1 mRNA expression in WT but not TTP KO cells. Confocal imaging of mitochondria showed profound fragmentation in WT cells exposed DFO that was abrogated in TTP KO cells. Functionally, iron chelation induced complete growth arrest in WT cells that was partially escaped by TTP KO cells. The increase in proliferation was accompanied by higher rates of cell death in TTP KO cells. Conclusions: Our studies show that TTP expression is upregulated under conditions of iron deficiency and in turn represses the expression of the mitochondrial fusion protein MFN1 to alter mitochondrial dynamics. By remodeling the mitochondria under conditions of iron deprivation we propose a critical role for TTP in coordinating growth arrest to protect metabolically active cells from cell death.

Endoplasmic reticulum-derived reactive oxygen species (ROS) is involved in toxicity of cell wall stress to Candida albicans

The cell wall is an important cell structure in both fungi and bacteria, and hence becomes a common antimicrobial target. The cell wall-perturbing agents disrupt synthesis and function of cell wall components, leading to cell wall stress and consequent cell death. However, little is known about the detailed mechanisms by which cell wall stress renders fungal cell death. In this study, we found that ROS scavengers drastically attenuated the antifungal effect of cell wall-perturbing agents to the model fungal pathogen Candida albicans, and these agents caused remarkable ROS accumulation and activation of oxidative stress response (OSR) in this fungus. Interestingly, cell wall stress did not cause mitochondrial dysfunction and elevation of mitochondrial superoxide levels. Furthermore, the iron chelator 2,2′-bipyridyl (BIP) and the hydroxyl radical scavengers could not attenuate cell wall stress-caused growth inhibition and ROS accumulation. However, cell wall stress up-regulated expression of unfold protein response (UPR) genes, enhanced protein secretion and promoted protein folding-related oxidation of Ero1, an important source of ROS production. These results indicated that oxidation of Ero1 in the endoplasmic reticulum (ER), rather than mitochondrial electron transport and Fenton reaction, contributed to cell wall stress-related ROS accumulation and consequent growth inhibition. Our findings uncover a novel link between cell wall integrity (CWI), ER function and ROS production in fungal cells, and shed novel light on development of strategies promoting the antifungal efficacy of cell wall-perturbing agents against fungal infections.

H6P2Mo18O62/Zn(BDC)(Bipy)0.5复合材料的合成、 表征及对亚甲基蓝的吸附

在溶剂热条件下，以H 6 P 2 Mo 18 O 62 、对苯二甲酸（H-2BDC）、4，4'-联吡啶（Bipy）和硝酸锌为原料构筑了1个三维金属有机骨架复合材料H 6 P 2 Mo 18 O 62 /Zn（BDC）（Bipy） 0.5 ，并采用红外光谱（IR）、X射线衍射（XRD）、扫描电子显微镜（SEM）、热重分析（TG）、N 2 吸附-脱附等手段对产物进行了表征. 同时，研究了产物对水溶液中亚甲基蓝（MB）的吸附性能，并探讨了MB初始pH值、初始浓度和温度对吸附量的影响. 结果表明，产物的等温吸附模型符合Langmuir等温吸附模型，动力学符合拟二级动力学. H 6 P 2 Mo 18 O 62 /Zn（BDC）（Bipy） 0.5 对亚甲基蓝的吸附是自发和放热的，此外，产物对甲基紫、罗丹明B、孔雀石绿等阳离子染料也具有良好的吸附性能.

Thermal Stability Study of Dye-Sensitized Solar Cells with Cobalt Bipyridyl–based Electrolytes

Dye-sensitized solar cells (DSSCs) with cobalt bipyridyl–based electrolytes can display higher solar cell performance than their iodide/triiodide counterpart. There is, however, little knowledge on their long term stability, which is a crucial aspect for potential commercial application. Herein, we studied the thermal stability of DSSCs using Co(bpy)32+/3+ redox electrolyte at 70°C in the dark for 50 days, combining 3 different additives, 4-tert-butylpyridine (TBP), 1-methylimidazole (MBI) and 2,2′-bipyridyl (BPY), in a nonvolatile solvent 3-methoxypropionitrile (MPN). Significant voltage decreases were found for all the studied solar cells, with a mechanism involving both a positive shift of the conduction band edge potential of TiO2 and a decreased electron lifetime, characterized by time resolved transient modulation techniques. Furthermore electrochemical impedance spectroscopy and differential pulse voltammetry studies indicate that the stability of Co(bpy)33+ is limited, causing an increased diffusion resistance in the electrolyte, but, surprisingly, no substantial change of the short-circuit current density (Jsc) in the devices. Overall, the DSSCs fabricated with the addition of both MBI and BPY in the electrolyte show the highest stability, maintaining 96% of its initial efficiency after 50 days, resulting from the overall compensation effects between the open circuit voltage decrease and the Jsc increase. These results provide insights about the degradation mechanism and emphasize the importance of the stability of TiO2/dye/electrolyte interface for the device stability under thermal stress.