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Scientific Reports Jun 2024A composite of Zinc oxide loaded with 5-weight % silver decorated on carbon nanotubes (Ag-loaded ZnO: CNT) was synthesized using a simple refluxed chemical method. The...
A composite of Zinc oxide loaded with 5-weight % silver decorated on carbon nanotubes (Ag-loaded ZnO: CNT) was synthesized using a simple refluxed chemical method. The influence of deviation in the weight % of carbon nanotube loading on photocatalytic dye degradation (methylene blue and rose bengal) and antibiotic (antimicrobial and antifungal) performance was investigated in this study. The light capture ability of Ag-loaded ZnO:CNT in the visible region was higher in photocatalytic activity than that of Ag-loaded ZnO and ZnO:CNT. The bandgap of the Ag-loaded ZnO: CNT was tuned owing to the surface plasmon resonance effect. The photocatalytic degradation investigations were optimized by varying the wt% in CNTs, pH of dye solution, concentration of the dye solution, and amount of catalytic dose. Around 100% photocatalytic efficiency in 2 min against MB dye was observed for Ag doped ZnO with 10 wt% CNT composite at pH 9, at a rate constant 1.48 min. Bipolaris sorokiniana fungus was first time tested against a composite material, which demonstrated optimum fungal inhibition efficiency of 48%. They were also tested against the bacterial strains Staphylococcus aureus, Bacillus cerius, Proteus vulgaris, and Salmonella typhimurium, which showed promising antibacterial activity compared to commercially available drugs. The composite of Ag doped ZnO with 5 wt% CNT has shown competitive zone inhibition efficacy of 21.66 ± 0.57, 15.66 ± 0.57, 13.66 ± 0.57 against bacterial strains Bacillus cerius, Proteus vulgaris, and Salmonella typhimurium which were tested for the first time against Ag-loaded ZnO:CNT.
Topics: Zinc Oxide; Silver; Nanotubes, Carbon; Anti-Bacterial Agents; Catalysis; Antifungal Agents; Staphylococcus aureus; Methylene Blue; Coloring Agents; Rose Bengal; Microbial Sensitivity Tests; Salmonella typhimurium; Hydrogen-Ion Concentration; Photolysis; Photochemical Processes
PubMed: 38890495
DOI: 10.1038/s41598-024-64746-6 -
Beilstein Journal of Organic Chemistry 2024Organic photocatalysts frequently possess dual singlet and triplet photoreactivity and a thorough photochemical characterization is essential for efficient light-driven...
Organic photocatalysts frequently possess dual singlet and triplet photoreactivity and a thorough photochemical characterization is essential for efficient light-driven applications. In this article, the mode of action of a polyazahelicene catalyst (Aza-H) was investigated using laser flash photolysis (LFP). The study revealed that the chromophore can function as a singlet-state photoredox catalyst in the sulfonylation/arylation of styrenes and as a triplet sensitizer in energy transfer catalysis. The singlet lifetime is sufficiently long to exploit the exceptional excited state reduction potential for the activation of 4-cyanopyridine. Photoinduced electron transfer generating the radical cation was directly observed confirming the previously proposed mechanism of a three-component reaction. Several steps of the photoredox cycle were investigated separately, providing deep insights into the complex mechanism. The triplet-excited Aza-H, which was studied with quantitative LFP, is formed with a quantum yield of 0.34. The pronounced triplet formation was exploited for the isomerization reaction of ()-stilbene to the -isomer and the cyclization of cinnamyl chloride. Catalyst degradation mainly occurs through the long-lived Aza-H triplet (28 µs), but the photostability is greatly increased when the triplet efficiently reacts in a catalytic cycle such that turnover numbers exceeding 4400 are achievable with this organocatalyst.
PubMed: 38887585
DOI: 10.3762/bjoc.20.106 -
Journal of Molecular Biology Jun 2024Heliorhodopsin (HeR) is a new rhodopsin family discovered in 2018 through functional metagenomic analysis. Similar to microbial rhodopsins, HeR has an all-trans retinal...
Heliorhodopsin (HeR) is a new rhodopsin family discovered in 2018 through functional metagenomic analysis. Similar to microbial rhodopsins, HeR has an all-trans retinal chromophore, and its photoisomerization to the 13-cis form triggers a relatively slow photocycle with sequential intermediate states (K, M, and O intermediates). The O intermediate has a relatively long lifetime and is a putative active state for transferring signals or regulating enzymatic reactions. Although the first discovered HeR, 48C12, was found in bacteria and the second HeR (TaHeR) was found in archaea, their key amino acid residues and molecular architectures have been recognized to be well conserved. Nevertheless, the rise and decay kinetics of the O intermediate are faster in 48C12 than in TaHeR. Here, using a new infrared spectroscopic technique with quantum cascade lasers, we clarified that the hydrogen bond between transmembrane helices (TM) 3 and 4 is essential for the altered O kinetics (Ser112 and Asn138 in 48C12). Interconverting mutants of 48C12 and TaHeR clearly revealed that the hydrogen bond is important for regulating the dynamics of the O intermediate. Overall, our study sheds light on the importance of the hydrogen bond between TM3 and TM4 in heliorhodopsins, similar to the DC gate in channelrhodopsins.
PubMed: 38880378
DOI: 10.1016/j.jmb.2024.168666 -
The Journal of Physical Chemistry. A Jun 2024Five biogenic unsaturated alcohols have been investigated under simulated atmospheric conditions regarding their gas-phase OH reactivity. The gas-phase rate coefficients...
Five biogenic unsaturated alcohols have been investigated under simulated atmospheric conditions regarding their gas-phase OH reactivity. The gas-phase rate coefficients of OH radicals with 2-methyl-3-buten-2-ol (), 3-methyl-2-buten-1-ol (), 3-methyl-3-buten-1-ol (), 2-methyl-3-buten-1-ol (), and 3-methyl-3-buten-2-ol () at 298 ± 2 K and 1000 ± 10 mbar total pressure of synthetic air were determined under low- and high-NO conditions using the relative kinetic technique. The present work provides for the first time the rate coefficients of gas-phase reactions of hydroxyl radicals with 2-methyl-3-buten-1-ol and 3-methyl-3-buten-2-ol. The following rate constants were measured (in 10 cm molecule s): = 6.32 ± 0.49, = 14.55 ± 0.93, = 10.04 ± 0.78, = 5.31 ± 0.37, and = 11.71 ± 1.29. No significant differences in the measured rate coefficients were obtained when either 365 nm photolysis of CHONO in the presence of NO or 254 nm photolysis of HO was used as a source of OH radicals. Reactivity toward other classes of related compounds such as alkenes and saturated alcohols is discussed. A comparison of the structure-activity relationship (SAR) estimates derived from the available accepted methodologies with experimental data available for unsaturated alcohols is provided. Atmospheric lifetimes for the investigated series of alkenols with respect to the main atmospheric oxidants are given and discussed.
PubMed: 38857889
DOI: 10.1021/acs.jpca.4c02287 -
Chemosphere Aug 2024This study aims the characterization of several tianeptine transformation products in ultrapure water by simulated sunlight irradiation. Tianeptine was completely...
This study aims the characterization of several tianeptine transformation products in ultrapure water by simulated sunlight irradiation. Tianeptine was completely degraded after 106 h of exposition following pseudo-first-order kinetics (half-life time = 12.0 ± 2.4 h). Furthermore, an ultra-high-performance liquid chromatography coupled with a high-resolution quadrupole time-of-flight-mass spectrometry method was developed and fully validated taking into account different method performance parameters for the quantification of tianeptine in river water up to a concentration of 400 pg L. Following a non-targeted approach based on mass data-independent acquisition, eight different transformation products not previously reported in the literature were identified and accordingly elucidated, proposing a photodegradation mechanism based on the accurate tandem mass spectrometry information acquired. Irradiation experiments were replicated for a tianeptine solution prepared in a blank river water sample, resulting in the formation of the same transformation products and similar degradation kinetics. In addition, a toxicity assessment of the photoproducts was performed by in silico method, being generally all TPs of comparable toxicity to the precursor except for TP1, and showing a similar persistence in the environment except for TP2 and TP6, while TP4 was the only TP predicted as mutagenic. The developed method was applied for the analysis of four river water samples.
Topics: Water Pollutants, Chemical; Tandem Mass Spectrometry; Chromatography, High Pressure Liquid; Photolysis; Thiazepines; Rivers; Kinetics; Sunlight
PubMed: 38849097
DOI: 10.1016/j.chemosphere.2024.142534 -
Analytical Chemistry Jun 2024Biopharmaceuticals, such as monoclonal antibodies (mAbs), need to maintain their chemical and physical stability in formulations throughout their lifecycle. It is known...
Biopharmaceuticals, such as monoclonal antibodies (mAbs), need to maintain their chemical and physical stability in formulations throughout their lifecycle. It is known that exposure of mAbs to light, particularly UV, triggers chemical and physical degradation, which can be exacerbated by trace amounts of photosensitizers in the formulation. Although routine assessments of degradation following defined UV dosages are performed, there is a fundamental lack of understanding regarding the intermediates, transient reactive species, and radicals formed during illumination, as well as their lifetimes and immediate impact post-illumination. In this study, we used light-coupled NMR spectroscopy to monitor in situ live spectral changes in sealed samples during and after UV-A illumination of different formulations of four mAbs without added photosensitizers. We observed a complex evolution of spectra, reflecting the appearance within minutes of transient radicals during illumination and persisting for minutes to tens of minutes after the light was switched off. Both mAb and excipient signals were strongly affected by illumination, with some exhibiting fast irreversible photodegradation and others exhibiting partial recovery in the dark. These effects varied depending on the mAb and the presence of excipients, such as polysorbate 80 (PS80) and methionine. Complementary ex situ high-performance size-exclusion chromatography analysis of the same formulations post-UV exposure in the chamber revealed significant loss of purity, confirming formulation-dependent degradation. Both approaches suggested the presence of degradation processes initiated by light but continuing in the dark. Further studies on photoreaction intermediates and transient reactive species may help mitigate the impact of light on biopharmaceutical degradation.
Topics: Antibodies, Monoclonal; Ultraviolet Rays; Magnetic Resonance Spectroscopy; Photolysis; Drug Compounding; Drug Stability; Light
PubMed: 38847283
DOI: 10.1021/acs.analchem.4c01164 -
Communications Chemistry Jun 2024Photolysis is an attractive method in organic synthesis to produce free radicals through direct bond cleavage. However, in this method, specific irradiation wavelengths...
Photolysis is an attractive method in organic synthesis to produce free radicals through direct bond cleavage. However, in this method, specific irradiation wavelengths of light have been considered indispensable for excitation through S-S or S-T transitions. Here we report the photoinduced homolysis of electronegative interelement bonds using light at wavelengths much longer than theoretically and spectroscopically predicted for the S-S or S-T transitions. This long-wavelength photolysis proceeds in N-Cl, N-F, and O-Cl bonds at room temperature under blue, green, and red LED irradiation, initiating diverse radical reactions. Through experimental, spectroscopic, and computational studies, we propose that this "hidden" absorption is accessible via electronic excitations from naturally occurring vibrationally excited ground states to unbonded excited states and is due to the electron-pair repulsion between electronegative atoms.
PubMed: 38834838
DOI: 10.1038/s42004-024-01208-0 -
Scientific Reports May 2024Photocatalysts of TiO-CuO coupled with 30% graphene oxide (GO) were hydrothermally fabricated, which varied the TiO to CuO weight ratios to 1:4, 1:2, 1:1, 2:1 and 4:1...
Photocatalysts of TiO-CuO coupled with 30% graphene oxide (GO) were hydrothermally fabricated, which varied the TiO to CuO weight ratios to 1:4, 1:2, 1:1, 2:1 and 4:1 and reduced to form TiO-CuO/reduced graphene oxide (rGO) photocatalysts. They were characterized using XRD, TEM, SEM, XPS, Raman, and DRS technologies. TiO-CuO composites and TiO-CuO/GO degrade methylene blue when persulfate ions are present. Persulfate concentration ranged from 1, 2, 4 to 8 mmol/dm in which the highest activity of 4.4 × 10 and 7.35 × 10 min was obtained with 4 mmol/dm for TiO-CuO (1:4) and TiO-CuO/GO (1:1), respectively. The presence of EDTA and isopropyl alcohol reduced the photodegradation. TiO-CuO coupled with rGO coagulates methylene blue in the presence of persulfate ions and such coagulation is independent of light. The catalyst dosage and the concentration of the dye were varied for the best-performing samples. The antibacterial activity of the synthesized samples was evaluated against the growth of Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa and Klebsiella pneumonia. Ti:Cu (1:2)-GO and Ti:Cu (1:4)-GO had the highest antibacterial activity against K. pneumoniae (16.08 ± 0.14 mm), P. aeruginosa (22.33 ± 0.58 mm), E. coli (16.17 ± 0.29 mm) and S. aureus (16.08 ± 0.88).
Topics: Graphite; Titanium; Copper; Anti-Bacterial Agents; Catalysis; Methylene Blue; Escherichia coli; Staphylococcus aureus; Photolysis; Sulfates
PubMed: 38822052
DOI: 10.1038/s41598-024-63452-7 -
Scientific Reports May 2024The textile dyeing and manufacturing industry is the major producer of significant amounts of wastewater that contain persistent substances such as azo dyes that require...
The textile dyeing and manufacturing industry is the major producer of significant amounts of wastewater that contain persistent substances such as azo dyes that require adequate remediation measures. Far ultraviolet at 222 nm light may provide an advantage for contaminants degradation as compared to conventional UV sources (254 nm). In this paper, the degradation of reactive black 5 (RB5) in artificial wastewater has been performed using a 222 nm Kr/Cl excimer source under direct photolysis and an advanced oxidation process using TiO/HO. The solution pH, catalyst concentration, 222 nm intensity, initial concentration of dye, and addition of HO influence the degradation rate constant. The molar absorption coefficient, quantum yield of RB5 at 222 nm and the electrical energy per order (EEO) from different treatment methods have been reported. RB5 shows 1.26 times higher molar absorption at 222 nm than at 254 nm. The EEO for excimer-222/HO ( 13 kWh/m) is five times lower than that of the excimer-222/TiO process, which makes the process energy efficient. The degradation of wastewater has been carried out at three distinct pH values (2, 6, and 10), and the pH level of 10 exhibited the highest degree of degradation. The degradation rate in the alkaline medium is 8.27 and 2.05 times higher than in the acidic or ambient medium. Since textile effluent is highly alkaline, this result is significant, as no neutralization of the wastewater is required, and direct treatment is possible. A possible degradation pathway has been established based on Fourier transform infrared spectroscopy (FTIR) and high resolution mass spectroscopy (HRMS) analysis. The phytotoxicity of the treated wastewater has also been evaluated for its suitability for reuse in agriculture. The study reveals that the excimer-222/HO treated wastewater significantly enhanced the germination percentage of Raphanus sativus seed (97%) compared to dye wastewater-grown seeds (75%). This work offers crucial information for future studies on the direct and indirect photolysis of azo dyes, as well as insight into the process of RB5 degradation under Kr/Cl excimer radiation.
PubMed: 38821987
DOI: 10.1038/s41598-024-63012-z -
Environmental Science & Technology Jun 2024Plastic pollution, a major environmental crisis, has a variety of consequences for various organisms within aquatic systems. Beyond the direct toxicity, plastic...
Plastic pollution, a major environmental crisis, has a variety of consequences for various organisms within aquatic systems. Beyond the direct toxicity, plastic pollution has the potential to absorb biological toxins and invasive microbial species. To better understand the capability of environmental plastic debris to adsorb these species, we investigated the binding of the model protein bovine serum albumin (BSA) to polyethylene (PE) films at various stages of photodegradation. Circular dichroism and fluorescence studies revealed that BSA undergoes structural rearrangement to accommodate changes to the polymer's surface characteristics (i.e., crystallinity and oxidation state) that occur as the result of photodegradation. To understand how protein structure may inform docking of whole organisms, we studied biofilm formation of bacteriaon the photodegraded PE. Interestingly, biofilms preferentially formed on the photodegraded PE that correlated with the state of weathering that induced the most significant structural rearrangement of BSA. Taken together, our work suggests that there are optimal physical and chemical properties of photodegraded polymers that predict which plastic debris will carry biochemical or microbial hitchhikers.
Topics: Serum Albumin, Bovine; Plastics; Animals; Cattle; Biofilms; Polyethylene; Photolysis
PubMed: 38809092
DOI: 10.1021/acs.est.3c10028