International Journal of Molecular Sciences

Editorial

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3 pages, 204 KiB

Open AccessEditorial

Electron and Photon Interactions with Bio (Related) Molecules

by Filipe Ferreira da Silva

Int. J. Mol. Sci. 2022, 23(24), 15491; https://doi.org/10.3390/ijms232415491 - 7 Dec 2022

Viewed by 891

Abstract

Part of the energy deposited in biological tissue by high-energy radiation is converted to secondary electrons. The knowledge at the molecular level on radiation interaction with biological species has increased due to the contributions of many different scientists working on radiation physics and [...] Read more.

Part of the energy deposited in biological tissue by high-energy radiation is converted to secondary electrons. The knowledge at the molecular level on radiation interaction with biological species has increased due to the contributions of many different scientists working on radiation physics and radiation chemistry. The intention of this Special Issue on electron and photon interactions with (bio) molecules is to bring together different areas of knowledge that focus on radiation interactions with matter. Full article

(This article belongs to the Special Issue Electron and Photon Interactions with Bio(Related) Molecules)

Research

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18 pages, 4659 KiB

Open AccessArticle

HF Formation through Dissociative Electron Attachment—A Combined Experimental and Theoretical Study on Pentafluorothiophenol and 2-Fluorothiophenol

by Maicol Cipriani and Oddur Ingólfsson

Int. J. Mol. Sci. 2022, 23(5), 2430; https://doi.org/10.3390/ijms23052430 - 23 Feb 2022

Cited by 7 | Viewed by 1950

Abstract

In chemoradiation therapy, dissociative electron attachment (DEA) may play an important role with respect to the efficiency of the radiosensitizers used. The rational tailoring of such radiosensitizers to be more susceptive to DEA may thus offer a path to increase their efficiency. Potentially, [...] Read more.

In chemoradiation therapy, dissociative electron attachment (DEA) may play an important role with respect to the efficiency of the radiosensitizers used. The rational tailoring of such radiosensitizers to be more susceptive to DEA may thus offer a path to increase their efficiency. Potentially, this may be achieved by tailoring rearrangement reactions into the DEA process such that these may proceed at low incident electron energies, where DEA is most effective. Favorably altering the orbital structure of the respective molecules through substitution is another path that may be taken to promote dissociation up on electron capture. Here we present a combined experimental and theoretical study on DEA in relation to pentafluorothiophenol (PFTP) and 2-fluorothiophenol (2-FTP). We investigate the thermochemistry and dynamics of neutral HF formation through DEA as means to lower the threshold for dissociation up on electron capture to these compounds, and we explore the influence of perfluorination on their orbital structure. Fragment ion yield curves are presented, and the thermochemical thresholds for the respective DEA processes are computed as well as the minimum energy paths for HF formation up on electron capture and the underlying orbital structure of the respective molecular anions. We show that perfluorination of the aromatic ring in these compounds plays an important role in enabling HF formation by further lowering the threshold for this process and through favorable influence on the orbital structure, such that DEA is promoted. We argue that this approach may offer a path for tailoring new and efficient radiosensitizers. Full article

(This article belongs to the Special Issue Electron and Photon Interactions with Bio(Related) Molecules)

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15 pages, 2928 KiB

Open AccessArticle

Influence of Hypoxia on Radiosensitization of Cancer Cells by 5-Bromo-2′-deoxyuridine

by Magdalena Zdrowowicz, Paulina Spisz, Aleksandra Hać, Anna Herman-Antosiewicz and Janusz Rak

Int. J. Mol. Sci. 2022, 23(3), 1429; https://doi.org/10.3390/ijms23031429 - 27 Jan 2022

Cited by 6 | Viewed by 2133

Abstract

Radiotherapy is a crucial cancer treatment, but its outcome is still far from satisfactory. One of the reasons that cancer cells show resistance to ionizing radiation is hypoxia, defined as a low level of oxygenation, which is typical for solid tumors. In the [...] Read more.

Radiotherapy is a crucial cancer treatment, but its outcome is still far from satisfactory. One of the reasons that cancer cells show resistance to ionizing radiation is hypoxia, defined as a low level of oxygenation, which is typical for solid tumors. In the hypoxic environment, cancer cells are 2–3 times more resistant to ionizing radiation than normoxic cells. To overcome this important impediment, radiosensitizers should be introduced to cancer therapy. When modified with an electrophilic substituent, nucleosides may undergo efficient dissociative electron attachment (DEA) that leaves behind nucleoside radicals, which, in secondary reactions, are able to induce DNA damage, leading to cancer cell death. We report the radiosensitizing effect of one of the best-known DEA-type radiosensitizers—5-bromo-2′-deoxyuridine (BrdU)—on breast (MCF-7) and prostate (PC3) cancer cells under both normoxia and hypoxia. MCF-7 and PC3 cells were treated with BrdU to investigate the effect of hypoxia on cell proliferation, incorporation into DNA and radiosensitivity. While the oxygen concentration did not significantly affect the efficiency of BrdU incorporation into DNA or the proliferation of tumor cells, the radiosensitizing effect of BrdU on hypoxic cells was more evident than on normoxic cells. Further mechanistic studies performed with the use of flow cytometry showed that under hypoxia, BrdU increased the level of histone H2A.X phosphorylation after X-ray exposure to a greater extent than under normal oxygenation conditions. These results confirm that the formation of double-strand breaks in hypoxic BrdU-treated cancer cells is more efficient. In addition, by performing stationary radiolysis of BrdU solution in the presence of an ^●OH radical scavenger, we compared the degree of its electron-induced degradation under aerobic and anaerobic conditions. It was determined that radiodegradation under anaerobic conditions was almost twice as high as that under aerobic conditions. Full article

(This article belongs to the Special Issue Electron and Photon Interactions with Bio(Related) Molecules)

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14 pages, 5035 KiB

Open AccessArticle

Total Electron Detachment and Induced Cationic Fragmentation Cross Sections for Superoxide Anion (O₂⁻) Collisions with Benzene (C₆H₆) Molecules

by Carlos Guerra, Sarvesh Kumar, Fernando Aguilar-Galindo, Sergio Díaz-Tendero, Ana I. Lozano, Mónica Mendes, Juan C. Oller, Paulo Limão-Vieira and Gustavo García

Int. J. Mol. Sci. 2022, 23(3), 1266; https://doi.org/10.3390/ijms23031266 - 23 Jan 2022

Cited by 1 | Viewed by 2478

Abstract

In this study, novel experimental total electron detachment cross sections for O₂⁻ collisions with benzene molecules are reported for the impact energy range (10–1000 eV), as measured with a transmission beam apparatus. By analysing the positively charged species produced during the [...] Read more.

In this study, novel experimental total electron detachment cross sections for O₂⁻ collisions with benzene molecules are reported for the impact energy range (10–1000 eV), as measured with a transmission beam apparatus. By analysing the positively charged species produced during the collision events, relative total ionisation cross sections were derived in the incident energy range of 160–900 eV. Relative partial ionisation cross sections for fragments with m/z ≤ 78 u were also given in this energy range. We also confirmed that heavier compounds (m/z > 78 u) formed for impact energies between 550 and 800 eV. In order to further our knowledge about the collision dynamics governing the fragmentation of such heavier molecular compounds, we performed molecular dynamics calculations within the framework of the Density Functional Theory (DFT). These results demonstrated that the fragmentation of these heavier compounds strongly supports the experimental evidence of m/z = 39–42, 50, 60 (u) cations formation, which contributed to the broad local maximum in the total ionisation observed from 550 to 800 eV. This work reveals the reactivity induced by molecular anions colliding with hydrocarbons at high energies, processes that can take place in the interstellar medium under various local conditions. Full article

(This article belongs to the Special Issue Electron and Photon Interactions with Bio(Related) Molecules)

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19 pages, 15126 KiB

Open AccessArticle

Effect of Humid Air Exposed to IR Radiation on Enzyme Activity

by Olga I. Yablonskaya, Vladimir L. Voeikov, Kirill N. Novikov, Ekaterina V. Buravleva, Valeriy A. Menshov and Aleksei V. Trofimov

Int. J. Mol. Sci. 2022, 23(2), 601; https://doi.org/10.3390/ijms23020601 - 6 Jan 2022

Cited by 1 | Viewed by 2721

Abstract

Water vapor absorbs well in the infra-red region of the electromagnetic spectrum. Absorption of radiant energy by water or water droplets leads to formation of exclusion zone water that possesses peculiar physico-chemical properties. In the course of this study, normally functioning and damaged [...] Read more.

Water vapor absorbs well in the infra-red region of the electromagnetic spectrum. Absorption of radiant energy by water or water droplets leads to formation of exclusion zone water that possesses peculiar physico-chemical properties. In the course of this study, normally functioning and damaged alkaline phosphatase, horseradish peroxidase and catalase were treated with humid air irradiated with infrared light with a wavelength in the range of 1270 nm and referred to as coherent humidity (CoHu). One-minute long treatment with CoHu helped to partially protect enzymes from heat inactivation, mixed function oxidation, and loss of activity due to partial unfolding. Authors suggest that a possible mechanism underlying the observed effects involves altering the physicochemical properties of aqueous media while treatment of the objects with CoHu where CoHu acts as an intermediary. Full article

(This article belongs to the Special Issue Electron and Photon Interactions with Bio(Related) Molecules)

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14 pages, 3206 KiB

Open AccessArticle

Pheomelanin Effect on UVB Radiation-Induced Oxidation/Nitration of l-Tyrosine

by Alessia Mariano, Irene Bigioni, Anna Scotto d’Abusco, Alessia Baseggio Conrado, Simonetta Maina, Antonio Francioso, Luciana Mosca and Mario Fontana

Int. J. Mol. Sci. 2022, 23(1), 267; https://doi.org/10.3390/ijms23010267 - 27 Dec 2021

Cited by 6 | Viewed by 3721

Abstract

Pheomelanin is a natural yellow-reddish sulfur-containing pigment derived from tyrosinase-catalyzed oxidation of tyrosine in presence of cysteine. Generally, the formation of melanin pigments is a protective response against the damaging effects of UV radiation in skin. However, pheomelanin, like other photosensitizing substances, can [...] Read more.

Pheomelanin is a natural yellow-reddish sulfur-containing pigment derived from tyrosinase-catalyzed oxidation of tyrosine in presence of cysteine. Generally, the formation of melanin pigments is a protective response against the damaging effects of UV radiation in skin. However, pheomelanin, like other photosensitizing substances, can trigger, following exposure to UV radiation, photochemical reactions capable of modifying and damaging cellular components. The photoproperties of this natural pigment have been studied by analyzing pheomelanin effect on oxidation/nitration of tyrosine induced by UVB radiation at different pH values and in presence of iron ions. Photoproperties of pheomelanin can be modulated by various experimental conditions, ranging from the photoprotection to the triggering of potentially damaging photochemical reactions. The study of the photomodification of l-Tyrosine in the presence of the natural pigment pheomelanin has a special relevance, since this tyrosine oxidation/nitration pathway can potentially occur in vivo in tissues exposed to sunlight and play a role in the mechanisms of tissue damage induced by UV radiation. Full article

(This article belongs to the Special Issue Electron and Photon Interactions with Bio(Related) Molecules)

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11 pages, 1310 KiB

Open AccessArticle

Absolute Differential Cross-Sections for Elastic Electron Scattering from Sevoflurane Molecule in the Energy Range from 50–300 eV

by Jelena Vukalović, Jelena B. Maljković, Francisco Blanco, Gustavo García, Branko Predojević and Bratislav P. Marinković

Int. J. Mol. Sci. 2022, 23(1), 21; https://doi.org/10.3390/ijms23010021 - 21 Dec 2021

Cited by 3 | Viewed by 2481

Abstract

We report the results of the measurements and calculations of the absolute differential elastic electron scattering cross-sections (DCSs) from sevoflurane molecule (C₄H₃F₇O). The experimental absolute DCSs for elastic electron scattering were obtained for the incident electron energies [...] Read more.

We report the results of the measurements and calculations of the absolute differential elastic electron scattering cross-sections (DCSs) from sevoflurane molecule (C₄H₃F₇O). The experimental absolute DCSs for elastic electron scattering were obtained for the incident electron energies from 50 eV to 300 eV, and for scattering angles from 25° to 125° using a crossed electron/target beams setup and the relative flow technique for calibration to the absolute scale. For the calculations, we have used the IAM-SCAR+I method (independent atom model (IAM) applying the screened additivity rule (SCAR) with interference terms included (I)). The molecular cross-sections were obtained from the atomic data by using the SCAR procedure, incorporating interference term corrections, by summing all the relevant atomic amplitudes, including the phase coefficients. In this approach, we obtain the molecular differential scattering cross-section (DCS), which, integrated over the scattered electron angular range, gives the integral scattering cross-section (ICS). Calculated cross-sections agree very well with experimental results, in the whole energy and angular range. Full article

(This article belongs to the Special Issue Electron and Photon Interactions with Bio(Related) Molecules)

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13 pages, 3306 KiB

Open AccessArticle

The Role of Low-Energy Electron Interactions in cis-Pt(CO)₂Br₂ Fragmentation

by Maicol Cipriani, Styrmir Svavarsson, Filipe Ferreira da Silva, Hang Lu, Lisa McElwee-White and Oddur Ingólfsson

Int. J. Mol. Sci. 2021, 22(16), 8984; https://doi.org/10.3390/ijms22168984 - 20 Aug 2021

Cited by 5 | Viewed by 1940

Abstract

Platinum coordination complexes have found wide applications as chemotherapeutic anticancer drugs in synchronous combination with radiation (chemoradiation) as well as precursors in focused electron beam induced deposition (FEBID) for nano-scale fabrication. In both applications, low-energy electrons (LEE) play an important role with regard [...] Read more.

Platinum coordination complexes have found wide applications as chemotherapeutic anticancer drugs in synchronous combination with radiation (chemoradiation) as well as precursors in focused electron beam induced deposition (FEBID) for nano-scale fabrication. In both applications, low-energy electrons (LEE) play an important role with regard to the fragmentation pathways. In the former case, the high-energy radiation applied creates an abundance of reactive photo- and secondary electrons that determine the reaction paths of the respective radiation sensitizers. In the latter case, low-energy secondary electrons determine the deposition chemistry. In this contribution, we present a combined experimental and theoretical study on the role of LEE interactions in the fragmentation of the Pt(II) coordination compound cis-PtBr₂(CO)₂. We discuss our results in conjunction with the widely used cancer therapeutic Pt(II) coordination compound cis-Pt(NH₃)₂Cl₂ (cisplatin) and the carbonyl analog Pt(CO)₂Cl₂, and we show that efficient CO loss through dissociative electron attachment dominates the reactivity of these carbonyl complexes with low-energy electrons, while halogen loss through DEA dominates the reactivity of cis-Pt(NH₃)₂Cl₂. Full article

(This article belongs to the Special Issue Electron and Photon Interactions with Bio(Related) Molecules)

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14 pages, 2339 KiB

Open AccessArticle

Experimental and Theoretical Studies of Dissociative Electron Attachment to Metabolites Oxaloacetic and Citric Acids

by Janina Kopyra, Paulina Wierzbicka, Adrian Tulwin, Guillaume Thiam, Ilko Bald, Franck Rabilloud and Hassan Abdoul-Carime

Int. J. Mol. Sci. 2021, 22(14), 7676; https://doi.org/10.3390/ijms22147676 - 18 Jul 2021

Cited by 5 | Viewed by 2520

Abstract

In this contribution the dissociative electron attachment to metabolites found in aerobic organisms, namely oxaloacetic and citric acids, was studied both experimentally by means of a crossed-beam setup and theoretically through density functional theory calculations. Prominent negative ion resonances from both compounds are [...] Read more.

In this contribution the dissociative electron attachment to metabolites found in aerobic organisms, namely oxaloacetic and citric acids, was studied both experimentally by means of a crossed-beam setup and theoretically through density functional theory calculations. Prominent negative ion resonances from both compounds are observed peaking below 0.5 eV resulting in intense formation of fragment anions associated with a decomposition of the carboxyl groups. In addition, resonances at higher energies (3–9 eV) are observed exclusively from the decomposition of the oxaloacetic acid. These fragments are generated with considerably smaller intensities. The striking findings of our calculations indicate the different mechanism by which the near 0 eV electron is trapped by the precursor molecule to form the transitory negative ion prior to dissociation. For the oxaloacetic acid, the transitory anion arises from the capture of the electron directly into some valence states, while, for the citric acid, dipole- or multipole-bound states mediate the transition into the valence states. What is also of high importance is that both compounds while undergoing DEA reactions generate highly reactive neutral species that can lead to severe cell damage in a biological environment. Full article

(This article belongs to the Special Issue Electron and Photon Interactions with Bio(Related) Molecules)

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13 pages, 2621 KiB

Open AccessArticle

Elastic Properties of Taurine Single Crystals Studied by Brillouin Spectroscopy

by Dong Hoon Kang, Soo Han Oh, Jae-Hyeon Ko, Kwang-Sei Lee and Seiji Kojima

Int. J. Mol. Sci. 2021, 22(13), 7116; https://doi.org/10.3390/ijms22137116 - 1 Jul 2021

Cited by 4 | Viewed by 2300

Abstract

The inelastic interaction between the incident photons and acoustic phonons in the taurine single crystal was investigated by using Brillouin spectroscopy. Three acoustic phonons propagating along the crystallographic b-axis were investigated over a temperature range of −185 to 175 °C. The temperature [...] Read more.

The inelastic interaction between the incident photons and acoustic phonons in the taurine single crystal was investigated by using Brillouin spectroscopy. Three acoustic phonons propagating along the crystallographic b-axis were investigated over a temperature range of −185 to 175 °C. The temperature dependences of the sound velocity, the acoustic absorption coefficient, and the elastic constants were determined for the first time. The elastic behaviors could be explained based on normal lattice anharmonicity. No evidence for the structural phase transition was observed, consistent with previous structural studies. The birefringence in the ac-plane indirectly estimated from the split longitudinal acoustic modes was consistent with one theoretical calculation by using the extrapolation of the measured dielectric functions in the infrared range. Full article

(This article belongs to the Special Issue Electron and Photon Interactions with Bio(Related) Molecules)

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27 pages, 6979 KiB

Open AccessArticle

Excited States of Bromopyrimidines Probed by VUV Photoabsorption Spectroscopy and Theoretical Calculations

by Mónica Mendes, Fábris Kossoski, Ana I. Lozano, João Pereira-da-Silva, Rodrigo Rodrigues, João Ameixa, Nykola C. Jones, Søren V. Hoffmann and Filipe Ferreira da Silva

Int. J. Mol. Sci. 2021, 22(12), 6460; https://doi.org/10.3390/ijms22126460 - 16 Jun 2021

Cited by 1 | Viewed by 2141

Abstract

We report absolute photoabsorption cross sections for gas-phase 2- and 5-bromopyrimidine in the 3.7–10.8 eV energy range, in a joint theoretical and experimental study. The measurements were carried out using high-resolution vacuum ultraviolet synchrotron radiation, with quantum chemical calculations performed through the nuclear [...] Read more.

We report absolute photoabsorption cross sections for gas-phase 2- and 5-bromopyrimidine in the 3.7–10.8 eV energy range, in a joint theoretical and experimental study. The measurements were carried out using high-resolution vacuum ultraviolet synchrotron radiation, with quantum chemical calculations performed through the nuclear ensemble approach in combination with time-dependent density functional theory, along with additional Franck–Condon Herzberg–Teller calculations for the first absorption band (3.7–4.6 eV). The cross sections of both bromopyrimidines are very similar below 7.3 eV, deviating more substantially from each other at higher energies. In the 7.3–9.0 eV range where the maximum cross-section is found, a single and broad band is observed for 5-bromopyrimidine, while more discernible features appear in the case of 2-bromopyrimidine. Several π* ← π transitions account for the most intense bands, while weaker ones are assigned to transitions involving the nitrogen and bromine lone pairs, the antibonding σ*_Br orbital, and the lower-lying Rydberg states. A detailed comparison with the available photo-absorption data of bromobenzene is also reported. We have found significant differences regarding the main absorption band, which is more peaked in bromobenzene, becoming broader and shifting to higher energies in both bromopyrimidines. In addition, there is a significant suppression of vibrational structures and of Rydberg states in the pair of isomers, most noticeably for 2-bromopyrimidine. Full article

(This article belongs to the Special Issue Electron and Photon Interactions with Bio(Related) Molecules)

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11 pages, 2310 KiB

Open AccessArticle

Double and Triple Differential Cross Sections for Single Ionization of Benzene by Electron Impact

by Ana I. Lozano, Filipe Costa, Xueguang Ren, Alexander Dorn, Lidia Álvarez, Francisco Blanco, Paulo Limão-Vieira and Gustavo García

Int. J. Mol. Sci. 2021, 22(9), 4601; https://doi.org/10.3390/ijms22094601 - 27 Apr 2021

Cited by 11 | Viewed by 2677

Abstract

Experimental results for the electron impact ionization of benzene, providing double (DDCS) and triple differential cross sections (TDCS) at the incident energy of 90 eV, measured with a multi-particle momentum spectrometer, are reported in this paper. The most intense ionization channel is assigned [...] Read more.

Experimental results for the electron impact ionization of benzene, providing double (DDCS) and triple differential cross sections (TDCS) at the incident energy of 90 eV, measured with a multi-particle momentum spectrometer, are reported in this paper. The most intense ionization channel is assigned to the parent ion (C₆H₆⁺) formation. The DDCS values are presented for three different transferred energies, namely 30, 40 and 50 eV. The present TDCS are given for two fixed values of the ejected electron energy (E₂), at 5 and 10 eV, and an electron scattering angle (θ₁) of 10°. Different features related to the molecular orbitals of benzene from where the electron is extracted are observed. In addition, a semi-empirical formula to be used as the inelastic angular distribution function in electron transport simulations has been derived from the present DDCS result and compared with other expressions available in the literature. Full article

(This article belongs to the Special Issue Electron and Photon Interactions with Bio(Related) Molecules)

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12 pages, 2412 KiB

Open AccessArticle

Ring-Selective Fragmentation in the Tirapazamine Molecule upon Low-Energy Electron Attachment

by Eugene Arthur-Baidoo, Joao Ameixa, Milan Ončák and Stephan Denifl

Int. J. Mol. Sci. 2021, 22(6), 3159; https://doi.org/10.3390/ijms22063159 - 19 Mar 2021

Cited by 9 | Viewed by 1945

Abstract

We investigate dissociative electron attachment to tirapazamine through a crossed electron–molecule beam experiment and quantum chemical calculations. After the electron is attached and the resulting anion reaches the first excited state, D₁, we suggest a fast transition into the ground electronic [...] Read more.

We investigate dissociative electron attachment to tirapazamine through a crossed electron–molecule beam experiment and quantum chemical calculations. After the electron is attached and the resulting anion reaches the first excited state, D₁, we suggest a fast transition into the ground electronic state through a conical intersection with a distorted triazine ring that almost coincides with the minimum in the D₁ state. Through analysis of all observed dissociative pathways producing heavier ions (90–161 u), we consider the predissociation of an OH radical with possible roaming mechanism to be the common first step. This destabilizes the triazine ring and leads to dissociation of highly stable nitrogen-containing species. The benzene ring is not altered during the process. Dissociation of small anionic fragments (NO₂⁻, CN₂⁻, CN⁻, NH₂⁻, O⁻) cannot be conclusively linked to the OH predissociation mechanism; however, they again do not require dissociation of the benzene ring. Full article

(This article belongs to the Special Issue Electron and Photon Interactions with Bio(Related) Molecules)

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14 pages, 2616 KiB

Open AccessArticle

Electronic Circular Dichroism of the Cas9 Protein and gRNA:Cas9 Ribonucleoprotein Complex

by Monika Halat, Magdalena Klimek-Chodacka, Jagoda Orleanska, Malgorzata Baranska and Rafal Baranski

Int. J. Mol. Sci. 2021, 22(6), 2937; https://doi.org/10.3390/ijms22062937 - 13 Mar 2021

Cited by 4 | Viewed by 4316

Abstract

The Streptococcus pyogenes Cas9 protein (SpCas9), a component of CRISPR-based immune system in microbes, has become commonly utilized for genome editing. This nuclease forms a ribonucleoprotein (RNP) complex with guide RNA (gRNA) which induces Cas9 structural changes and triggers its cleavage activity. Here, [...] Read more.

The Streptococcus pyogenes Cas9 protein (SpCas9), a component of CRISPR-based immune system in microbes, has become commonly utilized for genome editing. This nuclease forms a ribonucleoprotein (RNP) complex with guide RNA (gRNA) which induces Cas9 structural changes and triggers its cleavage activity. Here, electronic circular dichroism (ECD) spectroscopy was used to confirm the RNP formation and to determine its individual components. The ECD spectra had characteristic features differentiating Cas9 and gRNA, the former showed a negative/positive profile with maxima located at 221, 209 and 196 nm, while the latter revealed positive/negative/positive/negative pattern with bands observed at 266, 242, 222 and 209 nm, respectively. For the first time, the experimental ECD spectrum of the gRNA:Cas9 RNP complex is presented. It exhibits a bisignate positive/negative ECD couplet with maxima at 273 and 235 nm, and it differs significantly from individual spectrum of each RNP components. Additionally, the Cas9 protein and RNP complex retained biological activity after ECD measurements and they were able to bind and cleave DNA in vitro. Hence, we conclude that ECD spectroscopy can be considered as a quick and non-destructive method of monitoring conformational changes of the Cas9 protein as a result of Cas9 and gRNA interaction, and identification of the gRNA:Cas9 RNP complex. Full article

(This article belongs to the Special Issue Electron and Photon Interactions with Bio(Related) Molecules)

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14 pages, 3966 KiB

Open AccessArticle

Elastic Electron Scattering from Methane Molecule in the Energy Range from 50–300 eV

by Jelena Vukalović, Jelena B. Maljković, Karoly Tökési, Branko Predojević and Bratislav P. Marinković

Int. J. Mol. Sci. 2021, 22(2), 647; https://doi.org/10.3390/ijms22020647 - 11 Jan 2021

Cited by 9 | Viewed by 2151

Abstract

Electron interaction with methane molecule and accurate determination of its elastic cross-section is a demanding task for both experimental and theoretical standpoints and relevant for our better understanding of the processes in Earth’s and Solar outer planet atmospheres, the greenhouse effect or in [...] Read more.

Electron interaction with methane molecule and accurate determination of its elastic cross-section is a demanding task for both experimental and theoretical standpoints and relevant for our better understanding of the processes in Earth’s and Solar outer planet atmospheres, the greenhouse effect or in plasma physics applications like vapor deposition, complex plasma-wall interactions and edge plasma regions of Tokamak. Methane can serve as a test molecule for advancing novel electron-molecule collision theories. We present a combined experimental and theoretical study of the elastic electron differential cross-section from methane molecule, as well as integral and momentum transfer cross-sections in the intermediate energy range (50–300 eV). The experimental setup, based on a crossed beam technique, comprising of an electron gun, a single capillary gas needle and detection system with a channeltron is used in the measurements. The absolute values for cross-sections are obtained by relative-flow method, using argon as a reference. Theoretical results are acquired using two approximations: simple sum of individual atomic cross-sections and the other with molecular effect taken into the account. Full article

(This article belongs to the Special Issue Electron and Photon Interactions with Bio(Related) Molecules)

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