scholarly journals Enhancement of atmospheric H<sub>2</sub>SO<sub>4</sub>/H<sub>2</sub>O nucleation: organic oxidation products versus amines

2013 ◽  
Vol 13 (6) ◽  
pp. 16301-16335 ◽  
Author(s):  
T. Berndt ◽  
M. Sipilä ◽  
F. Stratmann ◽  
T. Petäjä ◽  
J. Vanhanen ◽  
...  
Keyword(s):  
Oxidation Products ◽  
Radical Scavenger ◽  
Oh Radicals ◽  
Oh Radical ◽  
Flow Tube ◽  
Experimental Conditions ◽  
Wide Range ◽  
Nucleation Mechanisms ◽  
Comparison Of The Results ◽  
Organic Oxidation

Abstract. Atmospheric H2SO4/H2O nucleation influencing effects have been studied in the flow tube IfT-LFT (Institute for Tropospheric Research – Laminar Flow Tube) at 293 ± 0.5 K and a pressure of 1 bar using synthetic air as the carrier gas. The presence of a possible background amine concentration in the order of 107–108 molecule cm−3 throughout the experiments has to be taken into account. In a first set of investigations, ozonolysis of olefins (tetramethylethylene, 1-methyl-cyclohexene, α-pinene and limonene) for close to atmospheric concentrations, served as the source of OH radicals and possibly other oxidants initiating H2SO4 formation starting from SO2. The oxidant generation is inevitably associated with the formation of a series of organic oxidation products arising from the parent olefins. These products (first generation mainly) showed no clear effect on the number of nucleated particles within a wide range of experimental conditions for H2SO4 concentrations higher than ~107 molecule cm−3. A comparison of the results of two different particle counters (50% cut-off size: about 1.5 nm or 2.5–3 nm) suggested that the early growth process of the nucleated particles was not significantly influenced by the organic oxidation products. An additional, H2SO4-independent process of particle (nano-CN) formation was observed in the case of α-pinene and limonene ozonolysis for H2SO4 concentrations smaller than ~10 7 molecule cm−3. Furthermore, the findings confirm the existence of an additional oxidant for SO2 beside OH radicals, very likely stabilized Criegee Intermediate (sCI). In the case of the ozonolysis of tetramethylethylene, the H2SO4 measurements in the absence and presence of an OH radical scavenger were well described by modelling using recently obtained kinetic data for the sCI reactivity in this system. A second set of experiments has been performed in the presence of added amines (trimethylamine, dimethylamine, aniline and pyridine) in the concentration range of a few 107–1010 molecule cm−3. Here, photolytic OH radical generation was applied for H2SO4 production with no addition of other organics. All amines showed a significant nucleation enhancement with increasing efficiency in the order pyridine < aniline < dimethylamine < trimethylamine. This result supports the idea of H2SO4 cluster stabilization by amines due to strong H2SO4 &amp;leftrightarrow; amine interactions. On the other hand, this study reveals that for organic oxidation products (in presence of the possible amine background as stated) a distinct H2SO4/H2O nucleation enhancement can be due to increased H2SO4 formation caused by additional organic oxidant production (sCI) rather than by stabilization of H2SO4 clusters due to H2SO4 &amp;leftrightarrow; organics interactions. However, because the molecular composition of nucleating clusters was not measured, the role of any background substances, unavoidably present in any system, to experimental data remains unclear. Also the experimental conditions do not cover fully the range of atmospheric observations, e.g., the concentration of precursor vapours represents rather the upper end of the atmospheric range. More experimental work is needed before definite conclusions about the nucleation mechanisms in the atmosphere can be drawn.

scholarly journals Enhancement of atmospheric H<sub>2</sub>SO<sub>4</sub> / H<sub>2</sub>O nucleation: organic oxidation products versus amines

2014 ◽  
Vol 14 (2) ◽  
pp. 751-764 ◽  
Author(s):  
T. Berndt ◽  
M. Sipilä ◽  
F. Stratmann ◽  
T. Petäjä ◽  
J. Vanhanen ◽  
...  
Keyword(s):  
First Generation ◽  
Oxidation Products ◽  
Oh Radicals ◽  
Flow Tube ◽  
Experimental Conditions ◽  
Criegee Intermediates ◽  
Wide Range ◽  
Independent Process ◽  
Oxidant Production ◽  
Organic Oxidation

Abstract. Atmospheric H2SO4 / H2O nucleation influencing effects have been studied in the flow tube IfT-LFT (Institute for Tropospheric Research – Laminar Flow Tube) at 293 ± 0.5 K and a pressure of 1 bar using synthetic air as the carrier gas. The presence of a possible background amine concentration in the order of 107–108 molecule cm−3 throughout the experiments has to be taken into account. In a first set of investigations, ozonolysis of olefins (tetramethylethylene, 1-methyl-cyclohexene, α-pinene and limonene) for close to atmospheric concentrations, served as the source of OH radicals and possibly other oxidants initiating H2SO4 formation starting from SO2. The oxidant generation is inevitably associated with the formation of organic oxidation products arising from the parent olefins. These products (first generation mainly) showed no clear effect on the number of nucleated particles within a wide range of experimental conditions for H2SO4 concentrations higher than ~107 molecule cm−3. Also the early growth process of the nucleated particles was not significantly influenced by the organic oxidation products in line with the expected growth by organic products using literature data. An additional, H2SO4-independent process of particle (nano-CN) formation was observed in the case of α-pinene and limonene ozonolysis for H2SO4 concentrations smaller than ~107 molecule cm−3. Furthermore, the findings confirm the appearance of an additional oxidant for SO2 beside OH radicals, very likely stabilized Criegee Intermediates (sCI). A second set of experiments has been performed in the presence of added amines in the concentrations range of a few 107–1010 molecule cm−3 applying photolytic OH radical generation for H2SO4 production without addition of other organics. All amines showed significant nucleation enhancement with increasing efficiency in the order pyridine < aniline < dimethylamine < trimethylamine. This result supports the idea of H2SO4 cluster stabilization by amines due to strong H2SO4↔amine interactions. On the other hand, this study indicates that for organic oxidation products (in presence of the possible amine background as stated) a distinct H2SO4 / H2O nucleation enhancement can be due to increased H2SO4 formation caused by additional organic oxidant production (sCI) rather than by stabilization of H2SO4 clusters due to H2SO4↔organics interactions.

Investigating the NO-dependent photooxidation of limonene by OH and O3 using the atmosphere simulation chamber SAPHIR

2021 ◽  
Author(s):  
Yat Sing Pang ◽  
Martin Kaminski ◽  
Anna Novelli ◽  
Philip Carlsson ◽  
Ismail-Hakki Acir ◽  
...  
Keyword(s):  
Organic Aerosol ◽  
Oxidation Products ◽  
Chemical Mechanism ◽  
Reaction Pathways ◽  
Oh Radicals ◽  
Oh Radical ◽  
Simulation Experiments ◽  
Master Chemical Mechanism ◽  
Simulation Results ◽  
Atmosphere Simulation Chamber

&lt;p&gt;Limonene is the fourth-most abundant monoterpene in the atmosphere, which upon oxidation leads to the formation of secondary organic aerosol (SOA) and thereby influences climate and air quality.&lt;/p&gt;&lt;p&gt;In this study, the oxidation of limonene by OH at different atmospherically relevant NO and HO&lt;sub&gt;2&lt;/sub&gt; levels (NO: 0.1 &amp;#8211; 10 ppb; HO&lt;sub&gt;2&lt;/sub&gt;: 20 ppt) was investigated in simulation experiments in the SAPHIR chamber at Forschungszentrum J&amp;#252;lich. The analysis focuses on comparing measured radical concentrations (RO&lt;sub&gt;2&lt;/sub&gt;, HO&lt;sub&gt;2&lt;/sub&gt;, OH) and OH reactivity (k&lt;sub&gt;OH&lt;/sub&gt;) with modeled values calculated using the Master Chemical Mechanism (MCM) version 3.3.1.&lt;/p&gt;&lt;p&gt;At high and medium NO concentrations, RO&lt;sub&gt;2&lt;/sub&gt; is expected to quickly react with NO. An HO&lt;sub&gt;2&lt;/sub&gt; radical is produced during the process that can be converted back to an OH radical by another reaction with NO. Consistently, for experiments conducted at medium NO levels (~0.5 ppb, RO&lt;sub&gt;2&lt;/sub&gt; lifetime ~10 s), simulated RO&lt;sub&gt;2&lt;/sub&gt;, HO&lt;sub&gt;2&lt;/sub&gt;, and OH agree with observations within the measurement uncertainties, if the OH reactivity of oxidation products is correctly described.&lt;/p&gt;&lt;p&gt;At lower NO concentrations, the regeneration of HO&lt;sub&gt;2&lt;/sub&gt; in the RO&lt;sub&gt;2&lt;/sub&gt; + NO reaction is slow and the reaction of RO&lt;sub&gt;2&lt;/sub&gt; with HO&lt;sub&gt;2&lt;/sub&gt; gains importance in forming peroxides. However, simulation results show a large discrepancy between calculated radical concentrations and measurements at low NO levels (&lt;0.1 ppb, RO&lt;sub&gt;2&lt;/sub&gt; lifetime ~ 100 s). Simulated RO&lt;sub&gt;2&lt;/sub&gt; concentrations are found to be overestimated by a factor of three; simulated HO&lt;sub&gt;2&lt;/sub&gt; concentrations are underestimated by 50 %; simulated OH concentrations are underestimated by about 35%, even if k&lt;sub&gt;OH&lt;/sub&gt; is correctly described. This suggests that there could be additional RO&lt;sub&gt;2&lt;/sub&gt; reaction pathways that regenerate HO&lt;sub&gt;2&lt;/sub&gt; and OH radicals become important, but they are not taken into account in the MCM model.&lt;/p&gt;

scholarly journals Highly Oxygenated Organic Molecules Produced by the Oxidation of Benzene and Toluene in a Wide Range of OH Exposure and NO<sub>x</sub> Conditions

2021 ◽  
Author(s):  
Xi Cheng ◽  
Qi Chen ◽  
Yong Jie Li ◽  
Yan Zheng ◽  
Keren Liao ◽  
...  
Keyword(s):  
Organic Molecules ◽  
Product Distribution ◽  
Flow Tube ◽  
Experimental Conditions ◽  
Effective Lifetime ◽  
Wide Range ◽  
Volatile Organic ◽  
Multifunctional Products ◽  
Oxidation Of Benzene ◽  
Oxygenated Products

Abstract. Oxidation of aromatic volatile organic compounds (VOCs) leads to the formation of tropospheric ozone and secondary organic aerosol, for which gaseous oxygenated products are important intermediates. We show herein experimental results of highly oxygenated organic molecules (HOMs) produced by the oxidation of benzene and toluene in a wide range of OH exposure and NOx conditions. The results suggest multi-generation OH oxidation plays an important role in the product distribution, which likely proceeds more preferably via H subtraction than OH addition for early-generation products from light aromatics. Our experimental conditions promote the formation of more oxygenated products than previous flow-tube studies. The formation of dimeric products however was suppressed and might be unfavorable under conditions of high OH exposure and low NOx in toluene oxidation. Under high-NOx conditions, nitrogen-containing multifunctional products are formed, while the formation of other HOMs is suppressed. Products containing two nitrogen atoms become more important as the NOx level increases, and the concentrations of these compounds depend significantly on NO2. The highly oxygenated nitrogen-containing products might be peroxyacylnitrates, implying a prolonged effective lifetime of RO2 that facilitates regional pollution. Our results call for further investigation on the roles of high-NO2 conditions in the oxidation of aromatic VOCs.

Importance of isomerization reactions for the OH radical regeneration from the photo-oxidation of isoprene investigated in the atmospheric simulation chamber SAPHIR

2020 ◽  
Author(s):  
Anna Novelli ◽  
Luc Vereecken ◽  
Birger Bohn ◽  
Hans-Peter Dorn ◽  
Georgios Gkatzelis ◽  
...  
Keyword(s):  
Oh Radicals ◽  
Oh Radical ◽  
Peroxy Radicals ◽  
Atmospheric Conditions ◽  
Unimolecular Reactions ◽  
Model Calculations ◽  
Hydrogen Shift ◽  
Wide Range ◽  
Regeneration Efficiency ◽  
Simulation Chamber

&lt;p&gt;Theoretical, laboratory and chamber studies have shown fast regeneration of hydroxyl radical (OH) in the photochemistry of isoprene largely due to previously disregarded unimolecular reactions which were previously thought not to be important under atmospheric conditions. Based on early field measurements, nearly complete regeneration was hypothesized for a wide range of tropospheric conditions, including areas such as the rainforest where slow regeneration of OH radicals is expected due to low concentrations of nitric oxide (NO). In this work the OH regeneration in the isoprene oxidation is directly quantified for the first time through experiments covering a wide range of atmospheric conditions (i.e. NO between 0.15 and 2 ppbv and temperature between 25 and 41&amp;#176;C) in the atmospheric simulation chamber SAPHIR. These conditions cover remote areas partially influenced by anthropogenic NO emissions, giving a regeneration efficiency of OH close to one, and areas like the Amazonian rainforest with very low NO, resulting in a surprisingly high regeneration efficiency of 0.5, i.e. a factor of 2 to 3 higher than explainable in the absence of unimolecular reactions. The measured radical concentrations were compared to model calculations and the best agreement was observed when at least 50% of the total loss of isoprene peroxy radicals conformers (weighted by their abundance) occurs via isomerization reactions for NO lower than 0.2 parts per billion (ppbv). For these levels of NO, up to 50% of the OH radicals are regenerated from the products of the 1,6 &amp;#945;-hydroxy-hydrogen shift (1,6-H shift) of Z-&amp;#948;-RO&lt;sub&gt;2 &lt;/sub&gt;radicals through photolysis of an unsaturated hydroperoxy aldehyde (HPALD) and/or through the fast aldehyde hydrogen shift (rate constant ~10 s&lt;sup&gt;-1&lt;/sup&gt; at 300K) in di-hydroperoxy carbonyl peroxy radicals (di-HPCARP-RO&lt;sub&gt;2&lt;/sub&gt;), depending on their relative yield. The agreement between all measured and modelled trace gases (hydroxyl, hydroperoxy and organic peroxy radicals, carbon monoxide and the sum of methyl vinyl ketone, methacrolein and hydroxyl hydroperoxides) is nearly independent on the adopted yield of HPALD and di-HPCARP-RO&lt;sub&gt;2&lt;/sub&gt; as both degrade relatively fast (&lt; 1 h), forming OH radical and CO among other products. Taking into consideration this and earlier isoprene studies, considerable uncertainties remain on the oxygenated products distribution, which affect radical levels and organic aerosol downwind of unpolluted isoprene dominated regions.&lt;/p&gt;

scholarly journals Investigation of the reaction of ozone with isoprene, methacrolein and methyl vinyl ketone using the HELIOS chamber

2017 ◽  
Vol 200 ◽  
pp. 289-311 ◽  
Author(s):  
Yangang Ren ◽  
Benoit Grosselin ◽  
Véronique Daële ◽  
Abdelwahid Mellouki
Keyword(s):  
Gas Phase ◽  
Organic Aerosol ◽  
Vinyl Ketone ◽  
Methyl Vinyl Ketone ◽  
Radical Scavenger ◽  
Oh Radical ◽  
Atmospheric Conditions ◽  
Experimental Conditions ◽  
Methyl Vinyl ◽  
Analytical Equipment

The rate constants for the ozonolysis of isoprene (ISO), methacrolein (MACR) and methyl vinyl ketone (MVK) have been measured using the newly built large volume atmospheric simulation chamber at CNRS-Orleans (France), HELIOS (Chambre de simulation atmosphérique à irradiation naturelle d’Orléans). The OH radical yields from the ozonolysis of isoprene, MACR and MVK have also been determined, as well as the gas phase stable products and their yields. The secondary organic aerosol yield for the ozonolysis of isoprene has been tentatively measured in the presence and absence of an OH radical scavenger. The measurements were performed under different experimental conditions with and without adding cyclohexane (cHX) as an OH radical scavenger. All experiments have been conducted at 760 torr of purified dry air (RH < 1%) and ambient temperature (T = 281–295 K). The data obtained are discussed and compared with those from the literature. The use of the HELIOS facility and its associated analytical equipment enables the derivation of kinetic parameters as well as mechanistic information under near realistic atmospheric conditions.

Oxidation of polycyclic aromatic hydrocarbons by ozone in the presence of sand

2001 ◽  
Vol 43 (5) ◽  
pp. 349-356 ◽  
Author(s):  
H. Choi ◽  
Y.-Y. Kim ◽  
H. Lim ◽  
J. Cho ◽  
J.-W. Kang ◽  
...  
Keyword(s):  
Removal Rate ◽  
Oh Radicals ◽  
Ozone Decomposition ◽  
Oh Radical ◽  
Soil Slurry ◽  
Experimental Conditions ◽  
Polycyclic Aromatic ◽  
Soil Media ◽  
The Given ◽  
Catalytic Ozone

A series of soil slurry experiments was performed to investigate the characteristics of PAHs removal by ozone in various conditions. Gaseous ozone was bottled into the aqueous phase in the presence of soil contaminated by PAHs. The effects of soil media, OH radical scavengers, ozone dosage, and humic acid were examined at the given experimental conditions. There exists a substantial difference in the removal of PAH according to the types of soil media tested. Baked sand showed the highest removal efficiency compared to the others. The descending order of removal rate was: BS&gt;S&gt;GB. This is considered to be due to the OH radical effect produced by catalytic reactions of ozone with the reactive site on the and. This is qualitatively proved by the experiment of scavenging OH radicals using tert-butanol. The comparison of half-lives of ozone in sand and glass bead columns further supports this hypothesis. It was found that about 22% of enhancement of phenanthrene destruction was accomplished by OH radicals produced by the catalytic ozone decomposition. The rate of ozone consumption for the phenanthrene oxidation was obtained as 1.88 mg/mgO3/min.

scholarly journals Importance of isomerization reactions for OH radical regeneration from the photo-oxidation of isoprene investigated in the atmospheric simulation chamber SAPHIR

2020 ◽  
Vol 20 (6) ◽  
pp. 3333-3355 ◽  
Author(s):  
Anna Novelli ◽  
Luc Vereecken ◽  
Birger Bohn ◽  
Hans-Peter Dorn ◽  
Georgios I. Gkatzelis ◽  
...  
Keyword(s):  
Relative Yield ◽  
Oh Radicals ◽  
Oh Radical ◽  
Peroxy Radicals ◽  
Unimolecular Reactions ◽  
Model Calculations ◽  
Hydrogen Shift ◽  
Wide Range ◽  
Regeneration Efficiency ◽  
Simulation Chamber

Abstract. Theoretical, laboratory, and chamber studies have shown fast regeneration of the hydroxyl radical (OH) in the photochemistry of isoprene, largely due to unimolecular reactions which were previously thought not to be important under atmospheric conditions. Based on early field measurements, nearly complete regeneration was hypothesized for a wide range of tropospheric conditions, including areas such as the rainforest where slow regeneration of OH radicals is expected due to low concentrations of nitric oxide (NO). In this work the OH regeneration in isoprene oxidation is directly quantified for the first time through experiments covering a wide range of atmospherically relevant NO levels (between 0.15 and 2 ppbv – parts per billion by volume) in the atmospheric simulation chamber SAPHIR. These conditions cover remote areas partially influenced by anthropogenic NO emissions, giving a regeneration efficiency of OH close to 1, and areas like the Amazonian rainforest with very low NO, resulting in a surprisingly high regeneration efficiency of 0.5, i.e. a factor of 2 to 3 higher than explainable in the absence of unimolecular reactions. The measured radical concentrations were compared to model calculations, and the best agreement was observed when at least 50 % of the total loss of isoprene peroxy radicals conformers (weighted by their abundance) occurs via isomerization reactions for NO lower than 0.2 ppbv. For these levels of NO, up to 50 % of the OH radicals are regenerated from the products of the 1,6 α-hydroxy-hydrogen shift (1,6-H shift) of Z-δ-RO2 radicals through the photolysis of an unsaturated hydroperoxy aldehyde (HPALD) and/or through the fast aldehydic hydrogen shift (rate constant ∼10 s−1 at 300 K) in di-hydroperoxy carbonyl peroxy radicals (di-HPCARP-RO2), depending on their relative yield. The agreement between all measured and modelled trace gases (hydroxyl, hydroperoxy, and organic peroxy radicals, carbon monoxide, and the sum of methyl vinyl ketone, methacrolein, and hydroxyl hydroperoxides) is nearly independent of the adopted yield of HPALD and di-HPCARP-RO2 as both degrade relatively fast (<1 h), forming the OH radical and CO among other products. Taking into consideration this and earlier isoprene studies, considerable uncertainties remain on the distribution of oxygenated products, which affect radical levels and organic aerosol downwind of unpolluted isoprene-dominated regions.

A new analytical method, using the dark Fenton reaction as an OH radical source to study oxidations of unsaturated (di)aldehydes in the aqueous phase

2021 ◽  
Author(s):  
Majda Mekic ◽  
Thomas Schaefer ◽  
Hartmut Herrmann
Keyword(s):  
Organic Compounds ◽  
Aqueous Phase ◽  
Phase Transfer ◽  
Catalytic Decomposition ◽  
Water Soluble ◽  
Radical Scavenger ◽  
Oh Radicals ◽  
Oh Radical ◽  
Fenton Chemistry ◽  
Typical Experiment

&lt;p&gt;Anthropogenic and biogenic sources produce numerous primary emitted gases, organic compounds, and aerosols in the atmosphere. An important group of such compounds are &amp;#945;, &amp;#946;-unsaturated carbonyl molecules, which can be formed in the atmosphere due to their secondary origin, including oxidation of their precursors such as hydrocarbons with common atmospheric oxidants such as hydroxyl radicals (&amp;#8231;OH). Since those compounds contain at least one double bond and one carbonyl group, they are characterized as water-soluble molecules, which can diffuse on the cloud droplets&amp;#8217; surface and undergo a phase transfer from the gas phase to the atmospheric aqueous phase. In the latter, the oxidized organic compounds can contribute to aerosol mass production through in-cloud processes, yielding aqueous phase secondary organic aerosols (aqSOA). Due to their strong photochemical behavior, the development of a new analytical approach for evaluating the OH radical kinetics in the aqueous phase under dark conditions was essential. One of the most studied non-photolytic reactions is Fenton chemistry (Fe(II)/H&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;2&lt;/sub&gt;), which serves as an OH radical source in the dark in the atmospheric aqueous phase after catalytic decomposition of H&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;2&lt;/sub&gt; in the presence of Fe(II) at acidic pH values. In a typical experiment, temperature-dependent second-order rate constants of OH radicals with unsaturated dialdehydes, such as (1) crotonaldehyde, and (2) 1,4-butenedial, were determined in a bulk reactor by using the competition kinetics method. In the newly developed method, the role of radical scavenger was performed by isotopically labeled 2-propanol (d8), while the OH-initiated oxidation produces deuterated acetone (d6), being analyzed with GC-MS after derivatization. The findings from our research will be incorporated in the CAPRAM model to explain discrepancies between experimentally observed and predicted aqSOA properties.&lt;/p&gt;

Strongly Coupled Redox-Linked Conformational Switching at the Active Site of the Non-Heme Iron-Dependent Dioxygenase, TauD

2019 ◽  
Author(s):  
Christopher John ◽  
Greg M. Swain ◽  
Robert P. Hausinger ◽  
Denis A. Proshlyakov
Keyword(s):  
Active Site ◽  
Structural Model ◽  
Heme Iron ◽  
Chemical Transformations ◽  
Experimental Conditions ◽  
Strongly Coupled ◽  
Non Heme Iron ◽  
Reversible Redox ◽  
Wide Range ◽  
Complex Structural

2-Oxoglutarate (2OG)-dependent dioxygenases catalyze C-H activation while performing a wide range of chemical transformations. In contrast to their heme analogues, non-heme iron centers afford greater structural flexibility with important implications for their diverse catalytic mechanisms. We characterize an <i>in situ</i> structural model of the putative transient ferric intermediate of 2OG:taurine dioxygenase (TauD) by using a combination of spectroelectrochemical and semi-empirical computational methods, demonstrating that the Fe (III/II) transition involves a substantial, fully reversible, redox-linked conformational change at the active site. This rearrangement alters the apparent redox potential of the active site between -127 mV for reduction of the ferric state and 171 mV for oxidation of the ferrous state of the 2OG-Fe-TauD complex. Structural perturbations exhibit limited sensitivity to mediator concentrations and potential pulse duration. Similar changes were observed in the Fe-TauD and taurine-2OG-Fe-TauD complexes, thus attributing the reorganization to the protein moiety rather than the cosubstrates. Redox difference infrared spectra indicate a reorganization of the protein backbone in addition to the involvement of carboxylate and histidine ligands. Quantitative modeling of the transient redox response using two alternative reaction schemes across a variety of experimental conditions strongly supports the proposal for intrinsic protein reorganization as the origin of the experimental observations.

scholarly journals Low-Energy Electron Damage to Condensed-Phase DNA and Its Constituents

2021 ◽  
Vol 22 (15) ◽  
pp. 7879
Author(s):  
Yingxia Gao ◽  
Yi Zheng ◽  
Léon Sanche
Keyword(s):  
Condensed Phase ◽  
Genetic Material ◽  
High Energy ◽  
Dna Lesions ◽  
Low Energy ◽  
Experimental Investigations ◽  
Experimental Conditions ◽  
Strand Breaks ◽  
Sequence Of Events ◽  
Wide Range

The complex physical and chemical reactions between the large number of low-energy (0–30 eV) electrons (LEEs) released by high energy radiation interacting with genetic material can lead to the formation of various DNA lesions such as crosslinks, single strand breaks, base modifications, and cleavage, as well as double strand breaks and other cluster damages. When crosslinks and cluster damages cannot be repaired by the cell, they can cause genetic loss of information, mutations, apoptosis, and promote genomic instability. Through the efforts of many research groups in the past two decades, the study of the interaction between LEEs and DNA under different experimental conditions has unveiled some of the main mechanisms responsible for these damages. In the present review, we focus on experimental investigations in the condensed phase that range from fundamental DNA constituents to oligonucleotides, synthetic duplex DNA, and bacterial (i.e., plasmid) DNA. These targets were irradiated either with LEEs from a monoenergetic-electron or photoelectron source, as sub-monolayer, monolayer, or multilayer films and within clusters or water solutions. Each type of experiment is briefly described, and the observed DNA damages are reported, along with the proposed mechanisms. Defining the role of LEEs within the sequence of events leading to radiobiological lesions contributes to our understanding of the action of radiation on living organisms, over a wide range of initial radiation energies. Applications of the interaction of LEEs with DNA to radiotherapy are briefly summarized.

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