Absolute cross sections of positive- and negative-ion production in electron collision with cytosine molecules

Abstract

Production of positive and negative ions of cytosine molecules (nucleic acid base) has been studied using a crossed electron and molecular beam technique. The method developed by the authors enabled the molecular beam intensity to be measured and the electron dependences and the absolute values of the total cross sections of production of both positive and negative cytosine ions to be determined. It has been shown that the total positive cytosine ion production cross section reaches its maximal value of 7.8 × 10−16 cm2 at the 78 eV electron energy. Dissociative ionization cross sections have also been determined. The maximum total negative cytosine ion production cross section was measured to be 4.2 × 10−18 cm2 at 1.5 eV.

Communication: Electron ionization of DNA bases

“…Our measurements on uracil 29 have also stressed the need for measurements on the DNA bases, as they gave cross sections about a factor of two larger than previously reported. 26 The limited absolute partial cross sections [23][24][25] that have been reported are also susceptible to similar uncertainties as in the total ion cross sections.…”

“…[20][21][22] So far, there exists only one set of absolute cross section measurements. [23][24][25][26] These measurements, carried out up to 200 eV of impact energies, vary from theory by a factor of 0.5-2 depending on the molecule. Even the large difference between the theory and these measurements does not show any consistency, though all of them have been made using the same experimental setup.…”

“…Even the large difference between the theory and these measurements does not show any consistency, though all of them have been made using the same experimental setup. [23][24][25][26] As a general thumb rule, for a given class of molecules like the DNA bases, one expects the cross sections to scale with the size of the molecule or molecular mass. The measured cross sections fail to conform to this thumb rule as they range from 8 A 2 for cytosine (mass = 111 amu) to 32 A 2 for guanine (mass = 151 amu).…”

Interaction of low-energy electrons with the purine bases, nucleosides, and nucleotides of DNA

“…Experimental studies of the nucleobases or their derivatives have overwhelmingly focused on dissociative attachment ͑DA͒, 7-31 though a few have examined electron-impact excitation [32][33][34][35][36][37] and ionization. 19,31,38 This effort has revealed the bond-selective nature of low-energy DA ͑Refs. 13, 16, and 23-27͒ and the important role that vibrational Feshbach resonances associated with dipole-bound anion states appear to play in driving such dissociation.…”

Quantum chemical study of the anionformation in thymidine and 5- bromouridine

“…Таким чином, радіаційно-індуковані процеси у живих клітинах мо-жуть бути змодельовані взаємодією пові-льних електронів з біомолекулами. Робо-ти, присвячені вивченню таких взаємодій з компонентами нуклеїнових кислот, вка-зують, що повільні електрони ефективно спричинюють дисоціативне збудження та іонізацію молекул [4][5][6], а також утворен-ня тимчасових негативних іонів через електронне захоплення [7][8][9][10]. Отже, аніо-ноутворення в компонентах нуклеїнових кислот, яке найбільш імовірне при міні-мальних енергіях, може служити адекват-ною моделлю для опису первинних про-цесів радіаційно-індукованого мутагенної загибелі.…”