Ion-beam radiation damage to DNA by investigation of free radical formation and base damage
Melis Kant, Pawel Jaruga, Erdem Coskun, Samuel Ward, Alexander Stark, David Becker, Amitav Adhikary, Michael Sevilla, M Miral Dizdar
This work investigated the physicochemical processes and DNA base products involved in Ne-22 ion- beam (ca. 1.4 GeV) radiation damage to hydrated (12 waters/nucleotide) highly polymerized salmon sperm DNA. For this purpose, approximately 12 small (ca. 10 mm x 4 mm x 1 mm) samples were stacked in a sample packet and then ion-beam irradiated at 77 K. Free radicals trapped in ion- beam irradiated DNA at 77 K were elucidated using ESR spectroscopy. After warming the samples to room temperature, the measurement of DNA base damage by GC-MS/MS and LC-MS/MS with isotope dilution revealed the formation of a plethora of products from all four DNA bases, and also the formation of 8,5′-cyclopurine-2′-deoxynucleosides, namely 5′R-cyclo-dAdo, 5′S-cyclo-dAdo, 5′R- cyclo-dGuo and 5′S-cyclo-dGuo. This work is the first to use the combination of ESR and mass spectrometry, enabling a better understanding of the mechanisms of radiation damage to DNA along the ion-beam track in terms of the formation of DNA free radicals and products. ESR measurements showed that, as the linear energy transfer (LET) profile of ion-beam radiation increases, the production of cation, anion and neutral radicals of DNA increases along the ion-beam track. The yields of DNA damage products along the ion-beam track were in excellent agreement with the radical production. Because the probability of recombination of DNA radicals in the core increases due to the rise in concentration of proximate ion radicals, the location of the highest energy deposition, the Bragg peak, may show different damage and may not be the location of the maximum damage. Supported by: NIH NCI grant R01CA04542, REF from CBR, OU, National Science Foundation under Grant No. CHE-1920110.
March 1-6, 2020
DNA Damage, Mutation and Cancer; Gordon Research Conference