Low-Energy (5-25 eV) Electron Damage to Homo-Oligonucleotides

• Published in: Radiation research 1999-03, Vol.151 (3), p.325-333
• Main Authors: Dugal, Pierre-Cyrille, Huels, Michael A., Sanche, Léon
• Format: Article
• Language: English
• Subjects: Anions; Biological and medical sciences; Biological effects of radiation; Desorption; DNA Damage; Electron energy; Electrons; Electrons - adverse effects; Flood damage; Fundamental and applied biological sciences. Psychology; In Vitro Techniques; Ionizing radiations; Molecules; Oligodeoxyribonucleotides - chemistry; Oligodeoxyribonucleotides - radiation effects; Oligonucleotides; Radiation damage; Radiochemistry; Residual gas; Solvents; Space life sciences; Tissues, organs and organisms biophysics
• ISSN: 0033-7587; 1938-5404
• DOI: 10.2307/3579945

Radiation-induced damage to homo-oligonucleotides is investigated by electron-stimulated desorption of neutral fragments from chemisorbed organic films. Six and 12 mers of cytidine phosphate (poly dCs) and thymidine phosphate (poly dTs) are chemisorbed from various solutions onto a crystalline gold substrate by a thiol modification at the 3′ end and are irradiated under ultra-high vacuum conditions with 5-25 eV electrons. The mass selected neutral desorption yields consist mainly of fragments of the DNA bases, i.e. CN and OCN (and/or ${\rm H}_{2}{\rm HCN}$ for poly dCs) from both poly dCs and poly dTs, indicating that the electrons interact specifically via fragmentation of the aromatic ring of either of the bases. Other heavier fragments are also detected such as ${\rm H}_{3}{\rm CC}-{\rm CO}$ from poly dTs. The yields generally process a threshold near 5 eV and a broad maximum around 12-13 eV incident electron energy. Dissociative electron attachments as well as electronically excited neutral or cation states are believed to be responsible for the various desorption yields. The latter yields are consistently larger for oligos chemisorbed from water and acetone solutions, compared to methanol solution. The invariance of the fragment yield intensities with oligo length suggests that the molecules are likely to adsorb almost parallel to the surface.