Combined experimental and theoretical study on the elastic electron scattering cross sections of ethanol

Combined theoretical and experimental studies on the elastic scattering of electrons on ethanol were performed in the energy range of 30–800 eV. The differential elastic electron scattering cross sections (DCS) of ethanol were measured for scattering angles of 30° to 150° using the relative flow technique and nitrogen (N2) as the reference gas. From these experimental DCS, integral elastic and momentum transfer cross sections were estimated. The comparison of the experimental results from the present work to those of other groups showed good agreement within the experimental uncertainty. In addition to the experimental determination, the DCS of ethanol were calculated by applying the independent atomic model with screening-corrected additivity rule and the modified independent atomic model. These theoretical calculations reproduced the experimental data well within the experimental uncertainty, with agreement better at high electron energies as was expected. Graphical abstract: [Figure not available: see fulltext.

Radiation-Induced Formation of 2′,3′-Dideoxyribonucleosides in DNA: A Potential Signature of Low-Energy Electrons

We have identified a series of modifications of the 2′-deoxyribose moiety of DNA arising from the exposure of isolated and cellular DNA to ionizing radiation. The modifications consist of 2′,3′-dideoxyribonucleoside derivatives of T, C, A, and G, as identified by enzymatic digestion and LC-MS/MS. Under dry conditions, the yield of these products was 6- to 44-fold lower than the yield of 8-oxo-7,8-dihydroguanine. We propose that 2′,3′-dideoxyribonucleosides are generated from the reaction of low-energy electrons with DNA, leading to cleavage of the C3′–O bond and formation of the corresponding C3′-deoxyribose radical

Fundamental Mechanisms of DNA Radiosensitization: Damage Induced by Low-Energy Electrons in Brominated Oligonucleotide Trimers

The replacement of nucleobases with brominated analogs enhances DNA radiosensitivity. We examine the chemistry of low-energy electrons (LEEs) in this sensitization process by experiments with thin films of the oligonucleotide trimers TBrXT, where BrX = 5-BrU (5-bromouracil), 5-BrC (5-bromocytosine), 8-BrA (8-bromoadenine), or 8-BrG (8-bromoguanine). The products induced from irradiation of thin (∼ 2.5 nm) oligonucleotide films, with 10 eV electrons, under ultrahigh vacuum (UHV) are analyzed by HPLC-UV. The number of damaged brominated trimers ranges from about 12 to 15 × 10^–3 molecules per incident electron, whereas under the identical conditions, these numbers drop to 4–7 × 10^–3 for the same, but nonbrominated oligonucleotides. The results of HPLC analysis show that the main degradation pathway of trinucleotides containing brominated bases involve debromination (i.e., loss of the bromine atom and its replacement with a hydrogen atom). The electron-induced sum of products upon bromination increases by factors of 2.1 for the pyrimidines and 3.2 for the purines. Thus, substitution of any native nucleobase with a brominated one in simple models of DNA increases LEE-induced damage to DNA and hence its radiosensitivity. Furthermore, besides the brominated pyrimidines that have already been tested in clinical trials, brominated purines not only appear to be promising sensitizers for radiotherapy, but could provide a higher degree of radiosensitization

Measurement of total electron scattering cross-section of N2O at intermediate energy region using a new magnetized electron beam apparatus

A new electron scattering apparatus is developed based on concepts from the positron system built by Surko et al (1988). In an electron version of the system, the electron beam is provided by a cathode and the rest of the system is correspondingly modified to a simpler system. The system was tested by measuring electron scattering from argon to verify its operation. N2O is important in the atmosphere and plasma processes, and in the intermediate energy region from 5 eV to 50 eV, there are two previous results for the electron scattering total cross-section which are in disagreement. We present here a new measurement for the total electron cross-section of N2O, helping to resolve this disagreement