D , O and OD desorption induced by low-energy (0–20 eV) electron impact on amorphous D2O films

Cold Plasma-Induced Modulation of Protein and Lipid Macromolecules: A Review

Nowadays, the food industry is prioritizing many innovative processing technologies that can produce minimally processed foods with superior and higher quality, lower costs, and faster operations. Among these advancements, cold plasma (CP) processing stands out for its remarkable capabilities in food preservation and extending the shelf life. Beyond its established role in microbial inactivation, CP has emerged as a transformative tool for modifying food biomolecules through reactive plasma species, addressing the versatile requirements of food industries for various applications. This review focuses on the interactions between reactive plasma species and essential food macromolecules, including proteins, lipids, and polysaccharides. The novelty lies in its detailed examination of how CP technology triggers structural, functional, and biochemical changes in proteins and lipids and explains the mechanisms involved. It connects fundamental molecular transformations to practical applications, such as enhanced protein functionality, lipid stabilization, and improved oxidative resistance. CP induces alterations in protein structure, especially in amino acid configurations, that can be applicable to the formulation of advanced gel, 3D printing, thermostable emulsions, enhanced solubility, and sensory materials. This review explores the ability of CP to modify protein allergenicity, its different effects on the mechanical and interfacial properties of proteins, and its role in the production of trans-fat-free oils. Despite its potential, a detailed understanding of the mechanism of CP's interactions with food macromolecules is also discussed. Furthermore, this review addresses key challenges and outlines future research opportunities, positioning CP as a sustainable and adaptable approach for innovating next-generation food systems. Further research is crucial to fully understand the potential of CP for food processing, followed by product development.

Synthesis of Resorcinol and Chlorophenol from Irradiation of 1,3-Dichlorobenzene in a Water Ice Environment by Low-Energy Electrons

Dichlorobenzene is beneficial to industries, however, the release of this compound into the environment causes significant damage to ecosystems and human health, as it exhibits resistance to biodegradation. Here, we show that chlorophenol and resorcinol are synthesized from 1,3-dichlorobenzene in a water ice environment (1) directly on a poly-crystalline gold surface and (2) after low-energy (<12 eV) electron irradiation of admixture films. For the latter, at energies below 5.5 eV, the electrons solely decompose the chlorinated compound into radicals that further undergo reaction with surrounding water molecules. At higher energies (i.e., >5.5 eV) additional fragments, e.g., hydroxyl radicals, produced from the dissociation of water molecules, may also be involved in the chemistry. The present results may suggest strategies for potential eco-friendly, sustainable, and scalable processes for the mitigation of these halogenated compounds such as cold plasma and radiation, in which low-energy (<10 eV) electrons are predominantly produced.

Desorption of neutrals, cations, and anions from core-excited amorphous solid water

Core-excitation of water ice releases many different molecules and ions in the gas phase. Studying these desorbed species and the underlying desorption mechanisms can provide useful information on the effects of x-ray irradiation in ice. We report a detailed study of the x-ray induced desorption of a number of neutral, cationic, and anionic species from amorphous solid water. We discuss the desorption mechanisms and the relative contributions of Auger and secondary electrons (x-ray induced electron stimulated desorption) and initial excitation (direct desorption) as well as the role of photochemistry. Anions are shown to desorb not just through processes linked with secondary electrons but also through direct dissociation of the core-excited molecule. The desorption spectra of oxygen ions (O⁺, OH⁺, H₂O⁺, O^-, and OH^-) give a new perspective on their previously reported very low desorption yields for most types of irradiations of water, showing that they mostly originate from the dissociation of photoproducts such as H₂O₂.

Electron-induced chemistry of methyl chloride caged within amorphous solid water

The interaction of low energy electrons (1.0-25 eV) with methyl-chloride (CD3Cl) molecules, caged within Amorphous Solid Water (ASW) films, 10-120 monolayer (ML) thick, has been studied on top of a Ru(0001) substrate under Ultra High Vacuum (UHV) conditions. While exposing the ASW film to 3 eV electrons a static electric field up to 8 × 10(8) V∕m is developed inside the ASW film due to the accumulation of trapped electrons that produce a plate capacitor voltage of exactly 3 V. At the same time while the electrons continuously strike the ASW surface, they are transmitted through the ASW film at currents of ca. 3 × 10(-7) A. These electrons transiently attach to the caged CD3Cl molecules leading to C-Cl bond scission via Dissociative Electron Attachment (DEA) process. The electron induced dissociation cross sections and product formation rate constants at 3.0 eV incident electrons at ASW film thicknesses of 10 ML and 40 ML were derived from model simulations supported by Thermal Programmed Desorption (TPD) experimental data. For 3.0 eV electrons the CD3Cl dissociation cross section is 3.5 × 10(-16) cm(2), regardless of ASW film thickness. TPD measurements reveal that the primary product is deuterated methane (D3CH) and the minor one is deuterated ethane (C2D6).

Influence of organic ions on DNA damage induced by 1 eV to 60 keV electrons

We report the results of a study on the influence of organic salts on the induction of single strand breaks (SSBs) and double strand breaks (DSBs) in DNA by electrons of 1 eV to 60 keV. Plasmid DNA films are prepared with two different concentrations of organic salts, by varying the amount of the TE buffer (Tris-HCl and EDTA) in the films with ratio of 1:1 and 6:1 Tris ions to DNA nucleotide. The films are bombarded with electrons of 1, 10, 100, and 60 000 eV under vacuum. The damage to the 3197 base-pair plasmid is analyzed ex vacuo by agarose gel electrophoresis. The highest yields are reached at 100 eV and the lowest ones at 60 keV. The ratios of SSB to DSB are surprisingly low at 10 eV (∼4.3) at both salt concentrations, and comparable to the ratios measured with 100 eV electrons. At all characteristic electron energies, the yields of SSB and DSB are found to be higher for the DNA having the lowest salt concentration. However, the organic salts are more efficient at protecting DNA against the damage induced by 1 and 10 eV electrons. DNA damage and protection by organic ions are discussed in terms of mechanisms operative at each electron energy. It is suggested that these ions create additional electric fields within the groove of DNA, which modify the resonance parameter of 1 and 10 eV electrons, namely, by reducing the electron capture cross-section of basic DNA units and the lifetime of corresponding transient anions. An interstrand electron transfer mechanism is proposed to explain the low ratios for the yields of SSB to those of DSB produced by 10 eV electrons.

Protection by organic ions against DNA damage induced by low energy electrons

It is well known that electrons below 15 eV induce strand breaks in DNA essentially via the formation of transient anions which decay by dissociative electron attachment (DEA) or into dissociative electronics states. The present article reports the results of a study on the influence of organic ions on this mechanism. tris and EDTA are incorporated at various concentrations within DNA films of different thicknesses. The amino group of tris molecules and the carboxylic acid function of ethylenediamine tetra-acetic acid (EDTA) molecules together can be taken as simple model for the amino acids components of proteins, such as histones, which are intimately associated with the DNA of eukaryotic cells. The yield of single strand breaks induced by 10 eV electrons is found to decrease dramatically as a function of the number of organic ions/nucleotide. As few as 2 organic ions/nucleotide are sufficient to decrease the yield of single strand breaks by 70%. This effect is partly explained by an increase in multiple inelastic electrons scattering with film thickness but changes in the resonance parameters can also contribute to DNA protection. This can occur if the electron captures cross section and the lifetime of the transient anions (i.e., core-excited resonances) formed at 10 eV are reduced by the presence of organic ions within the grooves of DNA. Moreover, it is proposed that the tris molecules may participate in the repair of DNA anions [such as G(-H)(-)] induced by DEA on DNA bases.

On the mechanism of anion desorption from DNA induced by low energy electrons

Our knowledge of the mechanisms of radiation damage to DNA induced by secondary electrons is still very limited, mainly due to the large sizes of the system involved and the complexity of the interactions. To reduce the problem to its simplest form, we investigated specific electron interactions with one of the most simple model system of DNA, an oligonucleotide tetrameter compound of the four bases. We report anion desorption yields from a thin solid film of the oligonucleotide GCAT induced by the impact of 3-15 eV electrons. All observed anions (H-, O-, OH-, CN-, and OCN-) are produced by dissociative electron attachment to the molecule, which results in desorption peaks between 6 and 12 eV. Above 14 eV nonresonant dipolar dissociation dominates the desorption yields. By comparing the shapes and relative intensities of the anion yield functions from GCAT physisorbed on a tantalum substrate with those obtained from isolated DNA basic subunits (i.e., bases, deoxyribose, and phosphate groups) from either the gas phase or condensed phase experiments, it is possible to obtain more details on the mechanisms involved in low energy electron damage to DNA, particularly on those producing single strand breaks.

Dissociative electron attachment to hydrated single DNA strands

The present experiments concern electron interactions with a film of short single strands of DNA covered by 3 monolayers of water, which corresponds to 5.25 water molecules per nucleotide. We report on the desorption of H{-}, O{-}, OH{-} from this target induced by 3-20 eV electrons. Below 15 eV, these anions emanate principally from a new type of dissociative core-excited transient anions formed via electron capture by a DNA- H2O complex. A smaller portion of the H{-} desorption signal arises from weakly bonded H2O molecules. The overall anion yield from DNA is increased by a factor of 1.6 owing to the presence of water.

Low-Energy (3−24 eV) Electron Damage to the Peptide Backbone

We report the mass spectrometric measurement of anions desorbed by 3-24 eV electron impact on thin films of formamide-1-d (DCONH2) and on the self-assembled monolayer (SAM) of two different Lys amide molecules used as a molecular model of the peptide backbone. In the present SAM configuration, the amides are elevated from a gold substrate by hydrocarbon chains to remove the effects of the metal substrate. Electron irradiation produces H- and D- from the formamide-1-d film and H-, CH3-, O-, and OH- from the SAM Lys amides. Below 13 eV, the dependence of the anion yields on the incident electron energy exhibits structures indicative of the dissociative electron attachment process, which is responsible for molecular fragmentation via the initial formation of core-excited anions. Above 13 eV, anion desorption is dominated principally by non-resonant dipolar dissociation. Our results suggest that the sensitivity of the peptide backbone to secondary electrons produced by ionizing radiation depends on the chemical environment (i.e., the amino acids sequence).

High resolution dissociative electron attachment to gas phase adenine

The dissociative electron attachment to the gas phase nucleobase adenine is studied using two different experiments. A double focusing sector field mass spectrometer is utilized for measurements requiring high mass resolution, high sensitivity, and relative ion yields for all the fragment anions and a hemispherical electron monochromator instrument for high electron energy resolution. The negative ion mass spectra are discussed at two different electron energies of 2 and 6 eV. In contrast to previous gas phase studies a number of new negative ions are discovered in the mass spectra. The ion efficiency curves for the negative ions of adenine are measured for the electron energy range from about 0 to 15 eV with an electron energy resolution of about 100 meV. The total anion yield derived via the summation of all measured fragment anions is compared with the total cross section for negative ion formation measured recently without mass spectrometry. For adenine the shape of the two cross section curves agrees well, taking into account the different electron energy resolutions; however, for thymine some peculiar differences are observed.

Mechanism and site of attack for direct damage to DNA by low-energy electrons

We report results on the desorption of OH- induced by 0-19 eV electrons incident on self-assembled monolayer films made of single and double DNA strands of different orientations with respect to a gold substrate. Such measurements make it possible to deduce the mechanism and site of OH- formation within a biomolecule as complex as DNA. This type of damage is attributed to dissociative electron attachment to the phosphate group of DNA, when it contains the counterion H+.