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Journal of Radiation Research May 2020Double-stranded oligonucleotides containing cisplatin adducts, with and without a mismatched region, were exposed to hydrated electrons generated by gamma-rays. Gel...
Double-stranded oligonucleotides containing cisplatin adducts, with and without a mismatched region, were exposed to hydrated electrons generated by gamma-rays. Gel electrophoresis analysis demonstrates the formation of cisplatin-interstrand crosslinks from the cisplatin-intrastrand species. The rate constant per base for the reaction between hydrated electrons and the double-stranded oligonucleotides with and without cisplatin containing a mismatched region was determined by pulse radiolysis to be 7 × 109 and 2 × 109 M-1 s-1, respectively. These results provide a better understanding of the radiosensitizing effect of cisplatin adducts in hypoxic tumors and of the formation of interstrand crosslinks, which are difficult for cells to repair.
Topics: Antineoplastic Agents; Cisplatin; Cross-Linking Reagents; DNA; DNA Adducts; Electrons; Humans; Hypoxia; Neoplasms; Nucleic Acid Conformation; Oligonucleotides; Pulse Radiolysis; Spectrometry, Mass, Electrospray Ionization
PubMed: 32211848
DOI: 10.1093/jrr/rraa014 -
Influence of Ionizing Radiation on Spontaneously Formed Aggregates in Proteins or Enzymes Solutions.Pharmaceutics Apr 2023We have shown that many proteins and enzymes (ovalbumin, β-lactoglobulin, lysozyme, insulin, histone, papain) undergo concentration-dependent reversible aggregation as...
We have shown that many proteins and enzymes (ovalbumin, β-lactoglobulin, lysozyme, insulin, histone, papain) undergo concentration-dependent reversible aggregation as a result of the interaction of the studied biomolecules. Moreover, irradiation of those protein or enzyme solutions under oxidative stress conditions results in the formation of stable soluble protein aggregates. We assume that protein dimers are mainly formed. A pulse radiolysis study has been made to investigate the early stages of protein oxidation by N3• or OH radicals. Reactions of the N3• radical with the studied proteins lead to the generation of aggregates stabilized by covalent bonds between tyrosine residues. The high reactivity of the OH with amino acids contained within proteins is responsible for the formation of various covalent bonds (including C-C or C-O-C) between adjacent protein molecules. In the analysis of the formation of protein aggregates, intramolecular electron transfer from the tyrosine moiety to Trp radical should be taken into account. Steady-state spectroscopic measurements with a detection of emission and absorbance, together with measurements of the dynamic scattering of laser light, made it possible to characterize the obtained aggregates. The identification of protein nanostructures generated by ionizing radiation using spectroscopic methods is difficult due to the spontaneous formation of protein aggregates before irradiation. The commonly used fluorescence detection of dityrosyl cross-linking (DT) as a marker of protein modification under the influence of ionizing radiation requires modification in the case of the tested objects. A precise photochemical lifetime measurement of the excited states of radiation-generated aggregates is useful in characterizing their structure. Resonance light scattering (RLS) has proven to be an extremely sensitive and useful technique to detect protein aggregates.
PubMed: 37242609
DOI: 10.3390/pharmaceutics15051367 -
Environmental Science & Technology May 2023Advanced reduction processes (ARP) have garnered increasing attention for the treatment of recalcitrant chemical contaminants, most notably per- and polyfluoroalkyl...
Advanced reduction processes (ARP) have garnered increasing attention for the treatment of recalcitrant chemical contaminants, most notably per- and polyfluoroalkyl substances (PFAS). However, the impact of dissolved organic matter (DOM) on the availability of the hydrated electron (e), the key reactive species formed in ARP, is not completely understood. Using electron pulse radiolysis and transient absorption spectroscopy, we measured bimolecular reaction rates constant for e reaction with eight aquatic and terrestrial humic substance and natural organic matter isolates ( ), with the resulting values ranging from (0.51 ± 0.01) to (2.11 ± 0.04) × 10 M s. measurements at varying temperature, pH, and ionic strength indicate that activation energies for diverse DOM isolates are ≈18 kJ mol and that could be expected to vary by less than a factor of 1.5 between pH 5 and 9 or from an ionic strength of 0.02 to 0.12 M. exhibited a significant, positive correlation to % carbonyl carbon for the isolates studied, but relationships to other DOM physicochemical properties were surprisingly more scattered. A 24 h UV/sulfite experiment employing chloroacetate as an e probe revealed that continued e exposure abates DOM chromophores and e scavenging capacity over a several hour time scale. Overall, these results indicate that DOM is an important e scavenger that will reduce the rate of target contaminant degradation in ARP. These impacts are likely greater in waste streams like membrane concentrates, spent ion exchange resins, or regeneration brines that have elevated DOM concentrations.
Topics: Dissolved Organic Matter; Water; Electrons; Water Pollutants, Chemical; Humic Substances
PubMed: 37141499
DOI: 10.1021/acs.est.3c00909 -
Heliyon Jul 2022Natural dietary products of health promoting and disease preventive functional relevance are gaining significant prominence. Current investigation was aimed to decipher...
Natural dietary products of health promoting and disease preventive functional relevance are gaining significant prominence. Current investigation was aimed to decipher the underlying molecular mechanism responsible for the antimutagenic action contributing to functional relevance of floral honey ('', Karanj honey) derived abscisic acid (ABA) against ethyl methanesulfonate (EMS) induced mutagenesis. Differential expression of proteins under different treatment conditions was ascertained by 2D gel electrophoresis. Selectively up-regulated characterized using MALDI-TOF MS/MS were identified as polyribonucleotide nucleotidyl transferse (PNPase), LPS-assembly lipoprotein (LptE), Outer membrane Usher protein (HtrE), ATP-dependent DNA helicase (RecG), and Phosphomethyl pyrimidine synthase (ThiC). Antimutagenicity exerted by ABA against EMS was ∼78% in wild type MG1655 strain however, in , this activity was found to be ∼60, 10, 9 and 10%, respectively. Proteomic analysis and antimutagenicity studies using single gene knockout strains thus indicated about the possible role of in observed antimutagenicity. Cyclic voltametry as well as competition kinetics through pulse radiolysis confirmed lack of antioxidant capacity in abscisic acid apparently ruling out the possibility of scavenging of electrophilic intermediates generated by ethyl methanesulfonate. It is proposed that ABA is exerting antimutagenicity through its involvement at the cellular level leading to physiological adaptation, strengthening of cell wall proteins and up-regulation of the repair proteins. This study provides a novel dimension to the functional role of abscisic acid from its nutraceutical perspective.
PubMed: 35874072
DOI: 10.1016/j.heliyon.2022.e09945 -
Astrobiology Sep 2018Hydrogen, produced by water radiolysis, has been suggested to support microbial communities on Mars. We quantitatively assess the potential magnitude of radiolytic H...
Hydrogen, produced by water radiolysis, has been suggested to support microbial communities on Mars. We quantitatively assess the potential magnitude of radiolytic H production in wet martian environments (the ancient surface and the present subsurface) based on the radionuclide compositions of (1) eight proposed Mars 2020 landing sites, and (2) three sites that individually yield the highest or lowest calculated radiolytic H production rates on Mars. For the proposed landing sites, calculated H production rates vary by a factor of ∼1.6, while the three comparison sites differ by a factor of ∼6. Rates in wet martian sediment and microfractured rock are comparable with rates in terrestrial environments that harbor low concentrations of microbial life (e.g., subseafloor basalt). Calculated H production rates for low-porosity (<35%), fine-grained martian sediment (0.12-1.2 nM/year) are mostly higher than rates for South Pacific subseafloor basalt (∼0.02-0.6 nM/year). Production rates in martian high-porosity sediment (>35%) and microfractured (1 μm) hard rock (0.03 to <0.71 nM/year) are generally similar to rates in South Pacific basalt, while yields for larger martian fractures (1 and 10 cm) are one to two orders of magnitude lower (<0.01 nM/year). If minerals or brine that amplify radiolytic H production rates are present, H yields exceed the calculated rates.
Topics: Extraterrestrial Environment; Geologic Sediments; Hydrogen; Mars; Pulse Radiolysis; Radioisotopes; Water
PubMed: 30048152
DOI: 10.1089/ast.2017.1654 -
Molecules (Basel, Switzerland) Dec 2019Oxidative damage to 2-thiouracil (2-TU) by hydroxyl (OH) and azide (N) radicals produces various primary reactive intermediates. Their optical absorption spectra and...
Oxidative damage to 2-thiouracil (2-TU) by hydroxyl (OH) and azide (N) radicals produces various primary reactive intermediates. Their optical absorption spectra and kinetic characteristics were studied by pulse radiolysis with UV-vis spectrophotometric and conductivity detection and by time-dependent density functional theory (TD-DFT) method. The transient absorption spectra recorded in the reactions of OH with 2-TU depend on the concentration of 2-TU, however, only slightly on pH. At low concentrations, they are characterized by a broad absorption band with a weakly pronounced maxima located at λ = 325, 340 and 385 nm, whereas for high concentrations, they are dominated by an absorption band with λ ≈ 425 nm. Based on calculations using TD-DFT method, the transient absorption spectra at low concentration of 2-TU were assigned to the OH-adducts to the double bond at C5 and C6 carbon atoms (3, 4) and 2c-3e bonded OH adduct to sulfur atom (1…OH) and at high concentration of 2-TU also to the dimeric 2c-3e S-S-bonded radical in neutral form (2). The dimeric radical (2) is formed in the reaction of thiyl-type radical (6) with 2-TU and both radicals are in an equilibrium with K = 4.2 × 10 M. Similar equilibrium (with K = 4.3 × 10 M) was found for pH above the pK of 2-TU which involves admittedly the same radical (6) but with the dimeric 2c-3e S-S bonded radical in anionic form (2). In turn, N-induced oxidation of 2-TU occurs via radical cation with maximum spin location on the sulfur atom which subsequently undergoes deprotonation at N1 atom leading again to thiyl-type radical (6). This radical is a direct precursor of dimeric radical (2).
Topics: Density Functional Theory; Electrons; Free Radicals; Hydrogen-Ion Concentration; Hydroxyl Radical; Kinetics; Oxidation-Reduction; Pulse Radiolysis; Radiation, Ionizing; Spectrum Analysis; Thiouracil
PubMed: 31810289
DOI: 10.3390/molecules24234402 -
Chemistry (Weinheim An Der Bergstrasse,... Aug 2020The directionality of the hole-transfer processes between DNA backbone and base was investigated by using phosphorodithioate [P(S )=S] components. ESR spectroscopy in...
The directionality of the hole-transfer processes between DNA backbone and base was investigated by using phosphorodithioate [P(S )=S] components. ESR spectroscopy in homogeneous frozen aqueous solutions and pulse radiolysis in aqueous solution at ambient temperature confirmed initial formation of G -P(S )=S. The ionization potential of G-P(S )=S was calculated to be slightly lower than that of guanine in 5'-dGMP. Subsequent thermally activated hole transfer from G to P(S )=S led to dithiyl radical (P-2S ) formation on the μs timescale. In parallel, ESR spectroscopy, pulse radiolysis, and density functional theory (DFT) calculations confirmed P-2S formation in an abasic phosphorodithioate model compound. ESR investigations at low temperatures and higher G-P(S )=S concentrations showed a bimolecular conversion of P-2S to the σ -σ* -bonded dimer anion radical [-P-2S 2S-P-] [ΔG (150 K, DFT)=-7.2 kcal mol ]. However, [-P-2S 2S-P-] formation was not observed by pulse radiolysis [ΔG° (298 K, DFT)=-1.4 kcal mol ]. Neither P-2S nor [-P-2S 2S-P-] oxidized guanine base; only base-to-backbone hole transfer occurs in phosphorodithioate.
Topics: Anions; DNA; Electron Spin Resonance Spectroscopy; Guanine; Nucleosides; Oxidation-Reduction; Phosphates; Pulse Radiolysis; Water
PubMed: 32059063
DOI: 10.1002/chem.202000247 -
Journal of Radiation Research Jun 2003Radiation-induced polymerization of vinylbenzyltrimethylammonium chloride (VBT) in aqueous solution has been investigated by steady-state and pulse radiolysis...
The role of radiolytically generated species in radiation-induced polymerization of vinylbenzyltrimethylammonium chloride (VBT) in aqueous solution: steady-state and pulse radiolysis study.
Radiation-induced polymerization of vinylbenzyltrimethylammonium chloride (VBT) in aqueous solution has been investigated by steady-state and pulse radiolysis techniques. The effects of dose, dose rate, monomer concentration, pH, and ambient conditions on steady state polymerization were investigated. The reactions of primary radicals of water radiolysis, such as OH radical, e(-)aq, and H atom, were studied. The reactions of other chemically active species such as O*-, oxidizing radicals such as N3*, Cl2(*-), Br(2*), SO4(*-), and a reducing specie such as CO2(*-) with VBT were also investigated. The reaction of VBT with OH radical and H atom were investigated by formation kinetics and by competition kinetics. The rate constant values for the reaction of OH radical with VBT were 4.7 x 10(9) dm3 mol(-1) s(-1) and 1.7 x 10(10) dm3 mol(-1) s(-1) by formation kinetics and by competition kinetics, respectively. The results indicate that OH radicals undergo electron transfer reactions (resulting in a radical cation) and addition reactions. The hydrated electron reacts with VBT with a rate constant of 1.9 x 10(10) dm3 mol(-1) s(-1) to form an anion. At pH approximately 1, H atom reaction with VBT is diffusion controlled with a rate constant of 5.1 x 10(9) dm3 mol(-1) s(-1) as determined by formation kinetics and 1.7 x 10(10) dm3 mol(-1) s(-1) as determined by competition kinetics. VBT radical anion reacts with VBT at a rate that is almost twice the rate at which VBT radical cation reacts with VBT, indicating anionic initiation of the polymerization of VBT. VBT undergoes very fast steady-state polymerization and dose rate; the presence of efficient radical quenchers such as oxygen and concentration of VBT in the aqueous solution affects the extent of polymerization. Typically, a dose of 4 kGy is sufficient to achieve 80-85% polymerization. The monomer solution shows a drastic increase in the viscosity of the solution, which finally gels to a soft rubbery mass.
Topics: Homeostasis; Polymers; Polystyrenes; Pulse Radiolysis; Quaternary Ammonium Compounds; Solutions; Water
PubMed: 13678346
DOI: 10.1269/jrr.44.161 -
Journal of Inorganic Biochemistry May 2018Iron regulatory proteins (IRPs), regulators of iron metabolism in mammalian cells, control the translation of proteins involved in iron uptake, storage and utilization...
Iron regulatory proteins (IRPs), regulators of iron metabolism in mammalian cells, control the translation of proteins involved in iron uptake, storage and utilization by binding to specific iron-responsive element (IRE) sequences of mRNAs. Two homologs of IRPs (IRP1 and IRP2) have a typical heme regulatory motif (HRM), a consensus sequence found in "heme-regulated proteins". However, specific heme binding to HRM has been reported only for IRP2, which is essential for oxidative modification and loss of binding to target mRNAs. In this paper, we confirmed that IRP1 also specifically binds two molar equivalents of heme, and found that the absorption and resonance Raman spectra of heme-bound IRP1 were quite similar to those of heme-bound IRP2. This shows that the heme environmental structures in IRP1 are close to those of proteins using heme as a regulatory molecule. Pulse radiolysis experiments, however, clearly revealed an axial ligand exchange from Cys to His immediately after the reduction of the heme iron to form a 5-coordinate His-ligated heme in heme-bound IRP2, whereas the 5-coordinate His-ligated heme was not observed after the reduction of heme-bound IRP1. Considering that the oxidative modification is only observed in heme-bound IRP2, but not IRP1, probably owing to the structural flexibility of IRP2, we propose that the transient 5-coordinate His-ligated heme is a prerequisite for oxidative modification of heme-bound IRP2, which functionally differentiates heme binding of IRP2 from that of IRP1.
Topics: Heme; Iron; Iron-Regulatory Proteins; Protein Binding
PubMed: 29449016
DOI: 10.1016/j.jinorgbio.2018.01.007 -
Nature Communications Nov 2023Time-resolved identification of surface-bound intermediates on metallic nanocatalysts is imperative to develop an accurate understanding of the elementary steps of CO...
Time-resolved identification of surface-bound intermediates on metallic nanocatalysts is imperative to develop an accurate understanding of the elementary steps of CO reduction. Direct observation on initial electron transfer to CO to form surface-bound CO radicals is lacking due to the technical challenges. Here, we use picosecond pulse radiolysis to generate CO via aqueous electron attachment and observe the stabilization processes toward well-defined nanoscale metallic sites. The time-resolved method combined with molecular simulations identifies surface-bound intermediates with characteristic transient absorption bands and distinct kinetics from nanosecond to the second timescale for three typical metallic nanocatalysts: Cu, Au, and Ni. The interfacial interactions are further investigated by varying the important factors, such as catalyst size and the presence of cation in the electrolyte. This work highlights fundamental ultrafast spectroscopy to clarify the critical initial step in the CO catalytic reduction mechanism.
PubMed: 37932333
DOI: 10.1038/s41467-023-42936-6