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The Journal of Physical Chemistry. B May 2024The migration of an electron-loss center (hole) in calf thymus DNA to bisbenzimidazole ligands bound in the minor groove is followed by pulse radiolysis combined with...
The migration of an electron-loss center (hole) in calf thymus DNA to bisbenzimidazole ligands bound in the minor groove is followed by pulse radiolysis combined with time-resolved spectrophotometry. The initially observed absorption spectrum upon oxidation of DNA by the selenite radical is consistent with spin on cytosine (C), as the GC pair neutral radical, followed by the spectra of oxidized ligands. The rate of oxidation of bound ligands increased with an increase in the ratio () ligands per base pair from 0.005 to 0.04. Both the rate of ligand oxidation and the estimated range of hole transfer (up to 30 DNA base pairs) decrease with the decrease in one-electron reduction potential between the GC pair neutral radical of ca. 1.54 V and that of the ligand radicals (', 0.90-0.99 V). Linear plots of log of the rate of hole transfer versus give a common intercept at = 0 and a free energy change of 12.2 ± 0.3 kcal mol, ascribed to the GC pair neutral radical undergoing a structural change, which is in competition to the observed hole transfer along DNA. The rate of hole transfer to the ligands at distance, , from the GC pair radical, , is described by the relationship = exp(constant/), where includes the rate constant for surmounting a small barrier.
Topics: DNA; Base Pairing; Free Radicals; Oxidation-Reduction; Benzimidazoles; Animals; Cattle; Ligands; Bisbenzimidazole; DNA Repair; DNA Damage; Cytosine
PubMed: 38686959
DOI: 10.1021/acs.jpcb.4c01069 -
The Journal of Physical Chemistry. B Sep 2023The decay kinetics of the hydrated electron (e) in aerosol OT (AOT)-based ternary microemulsions with pool sizes ranging from 0.34 to 4.85 nm were studied using...
Observation of Nanoconfinement Effect on the Kinetics of Hydrated Electron in the Nanoscale Water Pools of Water-AOT-Cyclohexane Microemulsions by Picosecond Pulse Radiolysis.
The decay kinetics of the hydrated electron (e) in aerosol OT (AOT)-based ternary microemulsions with pool sizes ranging from 0.34 to 4.85 nm were studied using picosecond pulse radiolysis coupled with transient absorption UV-vis spectroscopy. Electron transfer from oil to water and the subsequent solvation occurred within a time resolution of 7 ps. The decay kinetics of e were accurately modeled using a double-exponential decay model, revealing the occurrence of two types of reactions, i.e., the recombination reaction at the water-oil interface and the radical-radical reactions in the water pools. The apparent lifetimes of both types of decays decreased significantly as the size of water pools decreased, indicating the influence of nanoconfinement effects. Moreover, the importance of the water-oil interface increased with decreasing water content, regardless of the presence or absence of NO as an electron scavenger in the water pools. Our findings provide a comprehensive understanding on the kinetics of the radiation reaction in AOT-based microemulsions.
PubMed: 37681575
DOI: 10.1021/acs.jpcb.3c04302 -
International Journal of Molecular... Dec 2023In the retina, retinoids involved in vision are under constant threat of oxidation, and their oxidation products exhibit deleterious properties. Using pulse radiolysis,...
In the retina, retinoids involved in vision are under constant threat of oxidation, and their oxidation products exhibit deleterious properties. Using pulse radiolysis, this study determined that the bimolecular rate constants of scavenging cation radicals of retinoids by taurine are smaller than 2 × 10 Ms whereas lutein scavenges cation radicals of all three retinoids with the bimolecular rate constants approach the diffusion-controlled limits, while zeaxanthin is only 1.4-1.6-fold less effective. Despite that lutein exhibits greater scavenging rate constants of retinoid cation radicals than other antioxidants, the greater concentrations of ascorbate in the retina suggest that ascorbate may be the main protectant of all visual cycle retinoids from oxidative degradation, while α-tocopherol may play a substantial role in the protection of retinaldehyde but is relatively inefficient in the protection of retinol or retinyl palmitate. While the protection of retinoids by lutein and zeaxanthin appears inefficient in the retinal periphery, it can be quite substantial in the macula. Although the determined rate constants of scavenging the cation radicals of retinol and retinaldehyde by dopa-melanin are relatively small, the high concentration of melanin in the RPE melanosomes suggests they can be scavenged if they are in proximity to melanin-containing pigment granules.
Topics: Retinoids; Vitamin A; Melanins; Retinaldehyde; Lutein; Zeaxanthins; Taurine; Cations
PubMed: 38203675
DOI: 10.3390/ijms25010506 -
Physical Chemistry Chemical Physics :... Jan 2024The kinetics and mechanism of the reaction between OH radicals and ferrous ions in the temperature range 25-300 °C were studied using pulse radiolysis. At temperatures...
The kinetics and mechanism of the reaction between OH radicals and ferrous ions in the temperature range 25-300 °C were studied using pulse radiolysis. At temperatures <150 °C the rate of reaction is essentially independent of temperature, while at temperatures >150 °C the activation energy is 45.8 ± 3.0 kJ mol. The change in activation energy is attributed to a change in the dominant mechanism from hydrogen atom transfer (HAT) to dissociative ligand interchange. The kinetic isotope effect (KIE) was measured by repeating experiments in heavy water. A value of 2.9 was measured at room temperature where HAT is the dominant mechanism. The KIE decreases to zero at temperatures > 150 °C as ligand interchange becomes dominant and the O-H bond is no longer involved in the reaction.
PubMed: 38231479
DOI: 10.1039/d3cp03819j -
The Journal of Physical Chemistry. A Sep 2023Formal reduction potentials of highly oxidizing and short-lived radical cations of substituted biphenyls generated by pulse radiolysis in 1,2-dichloroethane (DCE) were...
Formal reduction potentials of highly oxidizing and short-lived radical cations of substituted biphenyls generated by pulse radiolysis in 1,2-dichloroethane (DCE) were measured using a redox equilibrium ladder method. The effect of halide ion-radical interactions on reduction potentials of biphenyls was examined by utilizing the ability of DCE to release Cl in the vicinity of the radical cation. The Hammett correlation of measured potentials across a range of over 700 mV shows saturation at high Hammett sigma values. This effect has been explained by both ion-pairing and hemicolligation interactions between biphenyl radical cations and Cl and appears to modulate reduction potentials by as much as 400 mV. This finding offers a convenient way to manipulate the energetics of electron transfer involving organic redox species.
PubMed: 37721794
DOI: 10.1021/acs.jpca.3c03817 -
Chemosphere May 2024The paper presents the results of studying the efficiency of the bisphenol A transformation in water exposed to ultraviolet radiation and a high-energy-pulse-electron...
The paper presents the results of studying the efficiency of the bisphenol A transformation in water exposed to ultraviolet radiation and a high-energy-pulse-electron beam (e-beam). It has been shown that in both cases, degradation of dissolved bisphenol A occurs, accompanied by an increase in the absorption coefficient in the wavelength region of more than 300 nm. After exposure, products were recorded that fluoresced in the region of more than λ = 400 nm. The fluorescent transformation product of bisphenol A in water (λ = 425 nm) was maximum formatted after an KrCl excilamp irradiated, and under the action of an e-beam, the accumulation of this product was minimal. Under e-beam radiation (170 keV) the efficiency of bisphenol A (1 mM) removal reached 97%. The data obtained allow us to develop ideas about photolysis and radiolysis in natural water systems when knowledge about targeted and optimal conditions for the degradation of bisphenol A is needed.
Topics: Benzhydryl Compounds; Phenols; Ultraviolet Rays; Photolysis; Water Pollutants, Chemical; Electrons; Water Purification
PubMed: 38556183
DOI: 10.1016/j.chemosphere.2024.141802 -
Advanced Science (Weinheim,... Jun 2024The 2-bit Lindqvist-type polyoxometalate (POM) [VO((OCH)CCHN)] with a diamagnetic {VO} core and azide termini shows six fully oxidized V centers in solution as well as...
The 2-bit Lindqvist-type polyoxometalate (POM) [VO((OCH)CCHN)] with a diamagnetic {VO} core and azide termini shows six fully oxidized V centers in solution as well as the solid state, according to V NMR spectroscopy. Under UV irradiation, it exhibits reversible switching between its ground S state and the energetically higher lying states in acetonitrile and water solutions. TD-DFT calculations demonstrate that this process is mainly initialized by excitation from the S to S state. Pulse radiolysis transient absorption spectroscopy experiments with a solvated electron point out photochemically induced charge disproportionation of V into V and electron communication between the POM molecules via their excited states. The existence of this unique POM-to-POM electron communication is also indicated by X-ray photoelectron spectroscopy (XPS) studies on gold-metalized silicon wafers (Au//SiO//Si) under ambient conditions. The amount of reduced vanadium centers in the "confined" environment increases substantially after beam irradiation with soft X-rays compared to non-irradiated samples. The excited state of one POM anion seems to give rise to subsequent electron transfer from another POM anion. However, this reaction is prohibited as soon as the relaxed T state of the POM is reached.
PubMed: 38868906
DOI: 10.1002/advs.202401595 -
Free Radical Research Jan 2024Bis(1-methylimidazol-2-yl) diselenide (MeImSe), a derivative of selenoneine, has been examined for bimolecular rate constants for scavenging of various radiolytically...
Bis(1-methylimidazol-2-yl) diselenide and its evaluation as a chemical radio-protector: role of kinetic rate constants for ROS scavenging and glutathione peroxidase like activity.
Bis(1-methylimidazol-2-yl) diselenide (MeImSe), a derivative of selenoneine, has been examined for bimolecular rate constants for scavenging of various radiolytically and non-radiolytically generated reactive oxygen species (ROS). Further, its potential to show glutathione peroxidase (GPx)-like activity and to protect models of DNA and lipid against radiation induced strand breakage and lipid peroxidation, respectively were studied. The results confirmed that MeImSe scavenged all major short-lived (hydroxyl radical) and long-lived (peroxyl radical, carbonate radical, nitrogen dioxide radical, hypochlorite and hydrogen peroxide) oxidants involved in the radiation toxicity either directly or through GPx-like catalytic mechanism. The rate constants of MeImSe for these oxidants were found to be comparable to analogous sulfur and selenium-based compounds. The enzyme kinetics study established that MeImSe took part in the GPx cycle through the reductive pathway. Further, MeImSe inhibited the radiation induced DNA strand cleavage and lipid peroxidation with half maximal inhibitory concentration (IC) of ∼ 60 μM and ∼100 μM, respectively. Interestingly, MeImSe treatment in the above concentration range (>100 μM) did not show any significant toxicity in normal human lung fibroblast (WI26) cells. The balance between efficacy and toxicity of MeImSe as a chemical radioprotector was attributed to the formation of less reactive intermediates during its oxidation/reduction reactions as evidenced from NMR studies.HighlightsMeImSe, a derivative of selenoneine protects DNA and lipid from radiation damageMeImSe scavenges all major short- and long-lived oxidants involved in radiation toxicityRate constants of MeImSe for ROS scavenging determined by pulse radiolysis techniqueFirst organoselenium compound reported to scavenge nitrogen dioxide radicalMeImSe exhibits GPx-like activity through reductive pathway.
Topics: Humans; Antioxidants; Reactive Oxygen Species; Glutathione Peroxidase; Nitrogen Dioxide; Organoselenium Compounds; Lipid Peroxidation; DNA; Oxidants; Lipids; Oxidation-Reduction; Histidine
PubMed: 38165076
DOI: 10.1080/10715762.2023.2299341 -
Physical Chemistry Chemical Physics :... Jan 2024Technetium is a problematic radioisotope for used nuclear fuel (UNF) and subsequent waste management owing to its high environmental mobility and coextraction in...
Technetium is a problematic radioisotope for used nuclear fuel (UNF) and subsequent waste management owing to its high environmental mobility and coextraction in reprocessing technologies as the pertechnetate anion (TcO). Consequently, several strategies are under development to control the transport of this radioisotope. A proposed approach is to use diaminoguanidine (DAG) for TcO and transuranic ion redox control. Although the initial DAG molecule is ultimately consumed in the redox process, its susceptibility to radiolysis is currently unknown under envisioned UNF reprocessing conditions, which is a critical knowledge gap for evaluating its overall suitability for this role. To this end, we report the impacts of steady-state gamma irradiation on the rate of DAG radiolysis in water, aqueous 2.0 M nitric acid (HNO), and in a biphasic solvent system composed of aqueous 2.0 M HNO in contact with 1.5 M ,-di-(2-ethylhexyl)isobutyramide (DEHiBA) dissolved in -dodecane. Additionally, we report chemical kinetics for the reaction of DAG with key transients arising from electron pulse radiolysis, specifically the hydrated electron (e), hydrogen atom (H˙), and hydroxyl (˙OH) and nitrate (NO˙) radicals. The DAG molecule exhibited significant reactivity with the ˙OH and NO˙ radicals, indicating that oxidation would be the predominant degradation pathway in radiation environments. This is consistent with its role as a reducing agent. Steady-state gamma irradiations demonstrated that DAG is readily degraded within a few hundred kilogray, the rate of which was found to increase upon going from water to HNO containing solutions and solvents systems. This was attributed to a thermal reaction between DAG and the predominant HNO radiolysis product, nitrous acid (HNO), (DAG + HNO) = 5480 ± 85 M s. Although no evidence was found for the radiolysis of DAG altering the radiation chemistry of the contacted DEHiBA/-dodecane phase in the investigated biphasic system, the utility of DAG as a redox control reagent will likely be limited by significant competition with its degradation by HNO.
PubMed: 38224090
DOI: 10.1039/d3cp04987f -
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