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Environmental Science and Pollution... Dec 2015The radiolytic decomposition of the drug diclofenac (DCF), and in limited extent, also two other widely used drugs, ibuprofen and carbamazepine, was examined using...
The radiolytic decomposition of the drug diclofenac (DCF), and in limited extent, also two other widely used drugs, ibuprofen and carbamazepine, was examined using liquid chromatography (LC) methods. The efficiency of DCF decomposition was examined in function of the absorbed dose of gamma radiation, and also in the presence of selected scavengers of radicals, which are commonly present in natural waters and wastes. Three different tests were employed for the monitoring of toxicity changes in the irradiated DCF solutions. The LC/mass spectrometry (MS) was used for the determination of products of DCF radiolysis. Using pulse-radiolysis method with the spectrophotometric detection, the rate constant values were determined for reactions of DCF with the main products of water radiolysis: hydroxyl radicals (1.24 ± 0.02) × 10(10) M(-1) s(-1) and hydrated electrons (3.1 ± 0.2) × 10(9) M(-1) s(-1). Their values indicate that both oxidative and reductive processes in radiolytic decomposition of DCF can take place in irradiated diluted aqueous solutions of DCF. The possibility of decomposition of all examined analytes was investigated in samples of river water and hospital waste. Compared to the previous studies, the conducted measurements in real samples were carried out at the concentration levels, which are close to those reported earlier in environmental samples. Graphical abstract ᅟ.
Topics: Chromatography, Liquid; Diclofenac; Gamma Rays; Hydroxyl Radical; Kinetics; Mass Spectrometry; Oxidation-Reduction; Poland; Pulse Radiolysis; Rivers; Spectrophotometry; Wastewater; Water Pollutants, Chemical; Water Purification
PubMed: 26308920
DOI: 10.1007/s11356-015-5236-6 -
Nature Aug 2014The proton gradient is a principal energy source for respiration-dependent active transport, but the structural mechanisms of proton-coupled transport processes are...
The proton gradient is a principal energy source for respiration-dependent active transport, but the structural mechanisms of proton-coupled transport processes are poorly understood. YiiP is a proton-coupled zinc transporter found in the cytoplasmic membrane of Escherichia coli. Its transport site receives protons from water molecules that gain access to its hydrophobic environment and transduces the energy of an inward proton gradient to drive Zn(II) efflux. This membrane protein is a well-characterized member of the family of cation diffusion facilitators that occurs at all phylogenetic levels. Here we show, using X-ray-mediated hydroxyl radical labelling of YiiP and mass spectrometry, that Zn(II) binding triggers a highly localized, all-or-nothing change of water accessibility to the transport site and an adjacent hydrophobic gate. Millisecond time-resolved dynamics reveal a concerted and reciprocal pattern of accessibility changes along a transmembrane helix, suggesting a rigid-body helical re-orientation linked to Zn(II) binding that triggers the closing of the hydrophobic gate. The gated water access to the transport site enables a stationary proton gradient to facilitate the conversion of zinc-binding energy to the kinetic power stroke of a vectorial zinc transport. The kinetic details provide energetic insights into a proton-coupled active-transport reaction.
Topics: Binding Sites; Biological Transport, Active; Escherichia coli Proteins; Hydrophobic and Hydrophilic Interactions; Hydroxyl Radical; Ion Transport; Kinetics; Mass Spectrometry; Membrane Transport Proteins; Models, Molecular; Protein Binding; Protein Conformation; Protons; Pulse Radiolysis; Water; X-Rays; Zinc
PubMed: 25043033
DOI: 10.1038/nature13382 -
International Journal of Molecular... Dec 2015Certain bactericidal antibiotics target mitochondrial components and, due to the leakage of electrons from the electron transport chain, one-electron reduction might...
Certain bactericidal antibiotics target mitochondrial components and, due to the leakage of electrons from the electron transport chain, one-electron reduction might occur that can lead to intermediates passing the electron to suitable acceptors. This study aimed at investigating the one-electron reduction mechanism of selected penicillin derivatives using pulse radiolysis techniques. Penicillins can accommodate the electron on each of their carbonyl carbon. Ketyl radicals are thus produced, which are reducing agents with possibility to interact with suitable biomolecules. A detailed mechanism of the reduction is reported.
Topics: Anti-Bacterial Agents; Kinetics; Oxidation-Reduction; Oxidative Stress; Penicillins; Pulse Radiolysis; Reactive Oxygen Species
PubMed: 26690427
DOI: 10.3390/ijms161226130 -
Nanomaterials (Basel, Switzerland) Dec 2020Gold nanoparticles are known to cause a radiosensitizing effect, which is a promising way to improve radiation therapy. However, the radiosensitization mechanism is not...
Gold nanoparticles are known to cause a radiosensitizing effect, which is a promising way to improve radiation therapy. However, the radiosensitization mechanism is not yet fully understood. It is currently assumed that gold nanoparticles can influence various physical, chemical, and biological processes. Pulse radiolysis is a powerful tool that can examine one of the proposed effects of gold nanoparticles, such as increased free radical production. In this work, we shed light on the consequence of ionizing radiation interaction with gold nanoparticles by direct measurements of solvated electrons using the pulse radiolysis technique. We found that at a therapeutically relevant gold concentration (<3 mM atomic gold, <600 μg × cm), the presence of gold nanoparticles in solution does not induce higher primary radicals' formation. This result indicates that energy absorption by gold nanoparticles and related effects such as higher ionization of surrounding media and OH radicals overproduction are not the reason for the radiosensitizing effect reported in the literature.
PubMed: 33321905
DOI: 10.3390/nano10122478 -
Nanomaterials (Basel, Switzerland) Jun 2024Ultra-small magnetic FeO nanoparticles are successfully synthesized in basic solutions by using the radiolytic method of the partial reduction in Fe in the presence of...
Ultra-small magnetic FeO nanoparticles are successfully synthesized in basic solutions by using the radiolytic method of the partial reduction in Fe in the presence of poly-acrylate (PA), or by using the coprecipitation method of Fe and Fe salts in the presence of PA. The optical, structural, and magnetic properties of the nanoparticles were examined using UV-Vis absorption spectroscopy, high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and SQUID magnetization measurements. The HRTEM and XRD analysis confirmed the formation of ultra-small magnetite nanoparticles in a spinel structure, with a smaller size for radiation-induced particles coated by PA (5.2 nm) than for coprecipitated PA-coated nanoparticles (11 nm). From magnetization measurements, it is shown that the nanoparticles are superparamagnetic at room temperature. The magnetization saturation value = 50.1 A m kg of radiation-induced nanoparticles at 60 kGy is higher than = 18.2 A m kg for coprecipitated nanoparticles. Both values are compared with nanoparticles coated with other stabilizers in the literature.
PubMed: 38921891
DOI: 10.3390/nano14121015 -
The Journal of Physical Chemistry... Sep 2018The primary localization process of radiation-induced charges (holes (cation radical sites) and excess electrons) remains poorly understood, even at the level of...
The primary localization process of radiation-induced charges (holes (cation radical sites) and excess electrons) remains poorly understood, even at the level of monomeric DNA/RNA models, in particular, in an aqueous environment. We report the first spectroscopic study of charge transfer occurring in radiolysis of aqueous uridine 5'-monophosphate (UMP) solutions and its components: uridine, uracil, ribose, and phosphate. Our results show that prehydrated electrons effectively attach to the base site of UMP; the holes in UMP formed by either direct ionization or reaction of UMP with the radiation-mediated water cation radical (HO) facilely localize on the ribose site, despite the fact that a part of them were initially created on either the phosphate or uracil. The nature of phosphate-to-sugar hole transfer is characterized as a barrierless intramolecular electron transfer with a time constant of 2.5 ns, while the base-to-sugar hole transfer occurs much faster, within a 5 ps electron pulse.
PubMed: 30132673
DOI: 10.1021/acs.jpclett.8b02170 -
Biochemistry Dec 2014Structural models of the fibrils formed by the 40-residue amyloid-β (Aβ40) peptide in Alzheimer's disease typically consist of linear polypeptide segments, oriented... (Comparative Study)
Comparative Study
Structural models of the fibrils formed by the 40-residue amyloid-β (Aβ40) peptide in Alzheimer's disease typically consist of linear polypeptide segments, oriented approximately perpendicular to the long axis of the fibril, and joined together as parallel in-register β-sheets to form filaments. However, various models differ in the number of filaments that run the length of a fibril, and in the topological arrangement of these filaments. In addition to questions about the structure of Aβ40 monomers in fibrils, there are important unanswered questions about their structure in prefibrillar intermediates, which are of interest because they may represent the most neurotoxic form of Aβ40. To assess different models of fibril structure and to gain insight into the structure of prefibrillar intermediates, the relative solvent accessibility of amino acid residue side chains in fibrillar and prefibrillar Aβ40 preparations was characterized in solution by hydroxyl radical footprinting and structural mass spectrometry. A key to the application of this technology was the development of hydroxyl radical reactivity measures for individual side chains of Aβ40. Combined with mass-per-length measurements performed by dark-field electron microscopy, the results of this study are consistent with the core filament structure represented by two- and three-filament solid state nuclear magnetic resonance-based models of the Aβ40 fibril (such as 2LMN , 2LMO , 2LMP , and 2LMQ ), with minor refinements, but they are inconsistent with the more recently proposed 2M4J model. The results also demonstrate that individual Aβ40 fibrils exhibit structural heterogeneity or polymorphism, where regions of two-filament structure alternate with regions of three-filament structure. The footprinting approach utilized in this study will be valuable for characterizing various fibrillar and nonfibrillar forms of the Aβ peptide.
Topics: Amyloid; Amyloid beta-Peptides; Chromatography, High Pressure Liquid; Cross-Linking Reagents; Electrophoresis, Polyacrylamide Gel; Humans; Hydroxyl Radical; Microscopy, Electron, Transmission; Models, Molecular; Molecular Weight; Pepsin A; Peptide Fragments; Peptide Mapping; Protein Conformation; Proteolysis; Pulse Radiolysis; Recombinant Proteins; Surface Properties; Synchrotrons; Tandem Mass Spectrometry
PubMed: 25382225
DOI: 10.1021/bi5010409 -
IUCrJ Jan 2018Synchrotron-based X-ray structural studies of ligand-bound enzymes are powerful tools to further our understanding of reaction mechanisms. For redox enzymes, it is...
Synchrotron-based X-ray structural studies of ligand-bound enzymes are powerful tools to further our understanding of reaction mechanisms. For redox enzymes, it is necessary to study both the oxidized and reduced active sites to fully elucidate the reaction, an objective that is complicated by potential X-ray photoreduction. In the presence of the substrate, this can be exploited to construct a structural movie of the events associated with catalysis. Using the newly developed approach of serial femtosecond rotation crystallography (SF-ROX), an X-ray damage-free structure of the as-isolated copper nitrite reductase (CuNiR) was visualized. The sub-10 fs X-ray pulse length from the SACLA X-ray free-electron laser allowed diffraction data to be collected to 1.6 Å resolution in a 'time-frozen' state. The extremely short duration of the X-ray pulses ensures the capture of data prior to the onset of radiation-induced changes, including radiolysis. Unexpectedly, an O ligand was identified bound to the T2Cu in a brand-new binding mode for a diatomic ligand in CuNiRs. The observation of O in a time-frozen structure of the as-isolated oxidized enzyme provides long-awaited clear-cut evidence for the mode of O binding in CuNiRs. This provides an insight into how CuNiR from can function as an oxidase, reducing O to HO, or as a superoxide dismutase (SOD) since it was shown to have ∼56% of the dismutase activity of the bovine SOD enzyme some two decades ago.
PubMed: 29354268
DOI: 10.1107/S2052252517016128 -
The Journal of Physical Chemistry. B Aug 2021The rate of formation of dichloride anions (Cl) in dilute aqueous solutions of HCl (2-100 mmol·kg) was measured by the technique of pulse radiolysis over the...
The rate of formation of dichloride anions (Cl) in dilute aqueous solutions of HCl (2-100 mmol·kg) was measured by the technique of pulse radiolysis over the temperature range of 288-373 K. The obtained Arrhenius dependence shows a concentration averaged activation energy of 7.3 ± 1.8 kJ·mol, being half of that expected from the mechanism assuming the OHCl intermediate and supporting the ionic equilibrium-based mechanism, i.e., the formation of Cl in the reaction of OH with a hydronium-chloride (Cl·HO) contact ion pair. Assuming diffusion-controlled encounter of the hydronium and chloride ions and including the effect of the ionic atmosphere, we showed that the reciprocal of τ, the lifetime of (Cl·HO), follows an Arrhenius dependence with an activation energy of 23 ± 4 kJ·mol, independent of the acid concentration. This result indicates that the contact pair is stabilized by hydrogen bonding interaction of the solvent molecules. We also found that at a fixed temperature, τ is noticeably increased in less-concentrated solutions ( < 0.01 m). Since this concentration effect is particularly pronounced at near ambient temperatures, the increasing pair lifetime may result from the solvent cage effect enhanced by the presence of large supramolecular structures (patches) formed by continuously connected four-bonded water molecules.
PubMed: 34383496
DOI: 10.1021/acs.jpcb.1c05642 -
The Journal of Physical Chemistry. B Jul 2015Pulse radiolysis measurements of the decay of hydrated electrons in solutions containing different concentrations of the oligonucleotide GTG with and without a cisplatin...
Pulse radiolysis measurements of the decay of hydrated electrons in solutions containing different concentrations of the oligonucleotide GTG with and without a cisplatin adduct show that the presence of a cisplatin moiety accelerates the reaction between hydrated electrons and the oligonucleotide. The rate constant of the reaction is found to be 2.23 × 10(10) mol(-1) L s(-1), which indicates that it is diffusion controlled. In addition, we show for the first time the formation of a Pt(I) intermediate as a result of the reaction of hydrated electrons with GTG-cisplatin. A putative reaction mechanism is proposed, which may form the basis of the radiosensitization of cancer cells in concomitant chemoradiation therapy with cisplatin.
Topics: Cisplatin; DNA Adducts; Electrons; Hydrolysis; Kinetics; Pulse Radiolysis
PubMed: 26098937
DOI: 10.1021/acs.jpcb.5b01752