International Journal of Molecular Sciences

Research

20 pages, 3503 KiB

Open AccessArticle

Electron Scattering from 1-Methyl-5-Nitroimidazole: Cross-Sections for Modeling Electron Transport through Potential Radiosensitizers

by Ana I. Lozano, Lidia Álvarez, Adrián García-Abenza, Carlos Guerra, Fábris Kossoski, Jaime Rosado, Francisco Blanco, Juan Carlos Oller, Mahmudul Hasan, Martin Centurion, Thorsten Weber, Daniel S. Slaughter, Deepthy M. Mootheril, Alexander Dorn, Sarvesh Kumar, Paulo Limão-Vieira, Rafael Colmenares and Gustavo García

Int. J. Mol. Sci. 2023, 24(15), 12182; https://doi.org/10.3390/ijms241512182 - 29 Jul 2023

Cited by 3 | Viewed by 1567

Abstract

In this study, we present a complete set of electron scattering cross-sections from 1-Methyl-5-Nitroimidazole (1M5NI) molecules for impact energies ranging from 0.1 to 1000 eV. This information is relevant to evaluate the potential role of 1M5NI as a molecular radiosensitizers. The total electron [...] Read more.

In this study, we present a complete set of electron scattering cross-sections from 1-Methyl-5-Nitroimidazole (1M5NI) molecules for impact energies ranging from 0.1 to 1000 eV. This information is relevant to evaluate the potential role of 1M5NI as a molecular radiosensitizers. The total electron scattering cross-sections (TCS) that we previously measured with a magnetically confined electron transmission apparatus were considered as the reference values for the present analysis. Elastic scattering cross-sections were calculated by means of two different schemes: The Schwinger multichannel (SMC) method for the lower energies (below 15 eV) and the independent atom model-based screening-corrected additivity rule with interferences (IAM-SCARI) for higher energies (above 15 eV). The latter was also applied to calculate the total ionization cross-sections, which were complemented with experimental values of the induced cationic fragmentation by electron impact. Double differential ionization cross-sections were measured with a reaction microscope multi-particle coincidence spectrometer. Using a momentum imaging spectrometer, direct measurements of the anion fragment yields and kinetic energies by the dissociative electron attachment are also presented. Cross-sections for the other inelastic channels were derived with a self-consistent procedure by sampling their values at a given energy to ensure that the sum of the cross-sections of all the scattering processes available at that energy coincides with the corresponding TCS. This cross-section data set is ready to be used for modelling electron-induced radiation damage at the molecular level to biologically relevant media containing 1M5NI as a potential radiosensitizer. Nonetheless, a proper evaluation of its radiosensitizing effects would require further radiobiological experiments. Full article

(This article belongs to the Special Issue Electron and Radical Induced Chemistry with Radiobiological Applications)

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25 pages, 8434 KiB

Open AccessArticle

Dependence of Induced Biological Damage on the Energy Distribution and Intensity of Clinical Intra-Operative Radiotherapy Electron Beams

by Rafael Colmenares, Rebeca Carrión-Marchante, M. Elena Martín, Laura Salinas Muñoz, María Laura García-Bermejo, Juan C. Oller, Antonio Muñoz, Francisco Blanco, Jaime Rosado, Ana I. Lozano, Sofía Álvarez, Feliciano García-Vicente and Gustavo García

Int. J. Mol. Sci. 2023, 24(13), 10816; https://doi.org/10.3390/ijms241310816 - 28 Jun 2023

Cited by 2 | Viewed by 1449

Abstract

The survival fraction of epithelial HaCaT cells was analysed to assess the biological damage caused by intraoperative radiotherapy electron beams with varying energy spectra and intensities. These conditions were achieved by irradiating the cells at different depths in water using nominal 6 MeV [...] Read more.

The survival fraction of epithelial HaCaT cells was analysed to assess the biological damage caused by intraoperative radiotherapy electron beams with varying energy spectra and intensities. These conditions were achieved by irradiating the cells at different depths in water using nominal 6 MeV electron beams while consistently delivering a dose of 5 Gy to the cell layer. Furthermore, a Monte Carlo simulation of the entire irradiation procedure was performed to evaluate the molecular damage in terms of molecular dissociations induced by the radiation. A significant agreement was found between the molecular damage predicted by the simulation and the damage derived from the analysis of the survival fraction. In both cases, a linear relationship was evident, indicating a clear tendency for increased damage as the averaged incident electron energy and intensity decreased for a constant absorbed dose, lowering the dose rate. This trend suggests that the radiation may have a more pronounced impact on surrounding healthy tissues than initially anticipated. However, it is crucial to conduct additional experiments with different target geometries to confirm this tendency and quantify the extent of this effect. Full article

(This article belongs to the Special Issue Electron and Radical Induced Chemistry with Radiobiological Applications)

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23 pages, 13872 KiB

Open AccessArticle

TRAX-CHEMxt: Towards the Homogeneous Chemical Stage of Radiation Damage

by Gianmarco Camazzola, Daria Boscolo, Emanuele Scifoni, Alexander Dorn, Marco Durante, Michael Krämer, Valentino Abram and Martina C. Fuss

Int. J. Mol. Sci. 2023, 24(11), 9398; https://doi.org/10.3390/ijms24119398 - 28 May 2023

Cited by 3 | Viewed by 2076

Abstract

The indirect effect of radiation plays an important role in radio-induced biological damages. Monte Carlo codes have been widely used in recent years to study the chemical evolution of particle tracks. However, due to the large computational efforts required, their applicability is typically [...] Read more.

The indirect effect of radiation plays an important role in radio-induced biological damages. Monte Carlo codes have been widely used in recent years to study the chemical evolution of particle tracks. However, due to the large computational efforts required, their applicability is typically limited to simulations in pure water targets and to temporal scales up to the µs. In this work, a new extension of TRAX-CHEM is presented, namely TRAX-CHEMxt, able to predict the chemical yields at longer times, with the capability of exploring the homogeneous biochemical stage. Based on the species coordinates produced around one track, the set of reaction–diffusion equations is solved numerically with a computationally light approach based on concentration distributions. In the overlapping time scale (500 ns–1 µs), a very good agreement to standard TRAX-CHEM is found, with deviations below 6% for different beam qualities and oxygenations. Moreover, an improvement in the computational speed by more than three orders of magnitude is achieved. The results of this work are also compared with those from another Monte Carlo-based algorithm and a fully homogeneous code (Kinetiscope). TRAX-CHEMxt will allow for studying the variation in chemical endpoints at longer timescales with the introduction, as the next step, of biomolecules, for more realistic assessments of biological response under different radiation and environmental conditions. Full article

(This article belongs to the Special Issue Electron and Radical Induced Chemistry with Radiobiological Applications)

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17 pages, 3463 KiB

Open AccessArticle

Track Structure of Light Ions: The Link to Radiobiology

by Valeria Conte, Anna Bianchi and Anna Selva

Int. J. Mol. Sci. 2023, 24(6), 5826; https://doi.org/10.3390/ijms24065826 - 18 Mar 2023

Cited by 6 | Viewed by 1322

Abstract

It is generally recognized that the biological response to irradiation by light ions is initiated by complex damages at the DNA level. In turn, the occurrence of complex DNA damages is related to spatial and temporal distribution of ionization and excitation events, i.e., [...] Read more.

It is generally recognized that the biological response to irradiation by light ions is initiated by complex damages at the DNA level. In turn, the occurrence of complex DNA damages is related to spatial and temporal distribution of ionization and excitation events, i.e., the particle track structure. It is the aim of the present study to investigate the correlation between the distribution of ionizations at the nanometric scale and the probability to induce biological damage. By means of Monte Carlo track structure simulations, the mean ionization yield

M_{1}

and the cumulative probabilities

F_{1}

,

F_{2}

, and

F_{3}

of at least one, two and three ionizations, respectively, were calculated in spherical volumes of water-equivalent diameters equal to 1, 2, 5 and 10 nm. When plotted as a function of

M_{1}

, the quantities

F_{1}

,

F_{2}

and

F_{3}

are distributed along almost unique curves, largely independent of particle type and velocity. However, the shape of the curves depends on the size of the sensitive volume. When the site size is 1 nm, biological cross sections are strongly correlated to combined probabilities of

F_{2}

and

F_{3}

calculated in the spherical volume, and the proportionality factor is the saturation value of biological cross sections. Full article

(This article belongs to the Special Issue Electron and Radical Induced Chemistry with Radiobiological Applications)

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14 pages, 973 KiB

Open AccessArticle

Charge Transfer and Electron Production in Proton Collisions with Uracil: A Classical and Semiclassical Study

by Clara Illescas, Luis Méndez, Santiago Bernedo and Ismanuel Rabadán

Int. J. Mol. Sci. 2023, 24(3), 2172; https://doi.org/10.3390/ijms24032172 - 21 Jan 2023

Viewed by 1645

Abstract

Cross sections for charge transfer and ionization in proton–uracil collisions are studied, for collision energies

0.05 < E < 2500

keV, using two computational models. At low energies, below 20 keV, the charge transfer total cross section is calculated employing a semiclassical close-coupling [...] Read more.

Cross sections for charge transfer and ionization in proton–uracil collisions are studied, for collision energies

0.05 < E < 2500

keV, using two computational models. At low energies, below 20 keV, the charge transfer total cross section is calculated employing a semiclassical close-coupling expansion in terms of the electronic functions of the supermolecule (H-uracil)

^{+}

. At energies above 20 keV, a classical-trajectory Monte Carlo method is employed. The cross sections for charge transfer at low energies have not been previously reported and have high values of the order of 40 Å

^{2}

, and, at the highest energies of the present calculation, they show good agreement with the previous results. The classical-trajectory Monte Carlo calculation provides a charge transfer and electron production cross section in reasonable agreement with the available experiments. The individual molecular orbital contributions to the total electron production and charge transfer cross sections are analyzed in terms of their energies; this permits the extension of the results to other molecular targets, provided the values of the corresponding orbital energies are known. Full article

(This article belongs to the Special Issue Electron and Radical Induced Chemistry with Radiobiological Applications)

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22 pages, 4178 KiB

Open AccessArticle

Radical Production with Pulsed Beams: Understanding the Transition to FLASH

by Andrea Espinosa-Rodriguez, Daniel Sanchez-Parcerisa, Paula Ibáñez, Juan Antonio Vera-Sánchez, Alejandro Mazal, Luis Mario Fraile and José Manuel Udías

Int. J. Mol. Sci. 2022, 23(21), 13484; https://doi.org/10.3390/ijms232113484 - 3 Nov 2022

Cited by 11 | Viewed by 2243

Abstract

Ultra-high dose rate (UHDR) irradiation regimes have the potential to spare normal tissue while keeping equivalent tumoricidal capacity than conventional dose rate radiotherapy (CONV-RT). This has been called the FLASH effect. In this work, we present a new simulation framework aiming to study [...] Read more.

Ultra-high dose rate (UHDR) irradiation regimes have the potential to spare normal tissue while keeping equivalent tumoricidal capacity than conventional dose rate radiotherapy (CONV-RT). This has been called the FLASH effect. In this work, we present a new simulation framework aiming to study the production of radical species in water and biological media under different irradiation patterns. The chemical stage (heterogeneous phase) is based on a nonlinear reaction-diffusion model, implemented in GPU. After the first 1 μs, no further radical diffusion is assumed, and radical evolution may be simulated over long periods of hundreds of seconds. Our approach was first validated against previous results in the literature and then employed to assess the influence of different temporal microstructures of dose deposition in the expected biological damage. The variation of the Normal Tissue Complication Probability (NTCP), assuming the model of Labarbe et al., where the integral of the peroxyl radical concentration over time (AUC-ROO) is taken as surrogate for biological damage, is presented for different intra-pulse dose rate and pulse frequency configurations, relevant in the clinical scenario. These simulations yield that overall, mean dose rate and the dose per pulse are the best predictors of biological effects at UHDR. Full article

(This article belongs to the Special Issue Electron and Radical Induced Chemistry with Radiobiological Applications)

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14 pages, 2361 KiB

Open AccessArticle

Electron Attachment to 5-Fluorouracil: The Role of Hydrogen Fluoride in Dissociation Chemistry

by Eugene Arthur-Baidoo, Gabriel Schöpfer, Milan Ončák, Lidia Chomicz-Mańka, Janusz Rak and Stephan Denifl

Int. J. Mol. Sci. 2022, 23(15), 8325; https://doi.org/10.3390/ijms23158325 - 28 Jul 2022

Cited by 9 | Viewed by 1805

Abstract

We investigate dissociative electron attachment to 5-fluorouracil (5-FU) employing a crossed electron-molecular beam experiment and quantum chemical calculations. Upon the formation of the 5-FU⁻ anion, 12 different fragmentation products are observed, the most probable dissociation channel being H loss. The parent anion, [...] Read more.

We investigate dissociative electron attachment to 5-fluorouracil (5-FU) employing a crossed electron-molecular beam experiment and quantum chemical calculations. Upon the formation of the 5-FU⁻ anion, 12 different fragmentation products are observed, the most probable dissociation channel being H loss. The parent anion, 5-FU⁻, is not stable on the experimental timescale (~140 µs), most probably due to the low electron affinity of FU; simple HF loss and F⁻ formation are seen only with a rather weak abundance. The initial dynamics upon electron attachment seems to be governed by hydrogen atom pre-dissociation followed by either its full dissociation or roaming in the vicinity of the molecule, recombining eventually into the HF molecule. When the HF molecule is formed, the released energy might be used for various ring cleavage reactions. Our results show that higher yields of the fluorine anion are most probably prevented through both faster dissociation of an H atom and recombination of F⁻ with a proton to form HF. Resonance calculations indicate that F⁻ is formed upon shape as well as core-excited resonances. Full article

(This article belongs to the Special Issue Electron and Radical Induced Chemistry with Radiobiological Applications)

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25 pages, 1784 KiB

Open AccessArticle

Simulating the Feasibility of Using Liquid Micro-Jets for Determining Electron–Liquid Scattering Cross-Sections

by Dale L. Muccignat, Peter W. Stokes, Daniel G. Cocks, Jason R. Gascooke, Darryl B. Jones, Michael J. Brunger and Ronald D. White

Int. J. Mol. Sci. 2022, 23(6), 3354; https://doi.org/10.3390/ijms23063354 - 20 Mar 2022

Cited by 6 | Viewed by 4986

Abstract

The extraction of electron–liquid phase cross-sections (surface and bulk) is proposed through the measurement of (differential) energy loss spectra for electrons scattered from a liquid micro-jet. The signature physical elements of the scattering processes on the energy loss spectra are highlighted using a [...] Read more.

The extraction of electron–liquid phase cross-sections (surface and bulk) is proposed through the measurement of (differential) energy loss spectra for electrons scattered from a liquid micro-jet. The signature physical elements of the scattering processes on the energy loss spectra are highlighted using a Monte Carlo simulation technique, originally developed for simulating electron transport in liquids. Machine learning techniques are applied to the simulated electron energy loss spectra, to invert the data and extract the cross-sections. The extraction of the elastic cross-section for neon was determined within 9% accuracy over the energy range 1–100 eV. The extension toward the simultaneous determination of elastic and ionisation cross-sections resulted in a decrease in accuracy, now to within 18% accuracy for elastic scattering and 1% for ionisation. Additional methods are explored to enhance the accuracy of the simultaneous extraction of liquid phase cross-sections. Full article

(This article belongs to the Special Issue Electron and Radical Induced Chemistry with Radiobiological Applications)

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