It　is　well　known　that　electrons　below　15　eV　induce　strand　breaks　in　DNA　essentially　via　the　formation　of　transient　anions　which　decay　by　dissociative　electron　attachment　(DEA)　or　into　dissociative　electronics　states.　The　present　article　reports　the　results　of　a　study　on　the　influence　of　organic　ions　on　this　mechanism.　tris　and　EDTA　are　incorporated　at　various　concentrations　within　DNA　films　of　different　thicknesses.　The　amino　group　of　tris　molecules　and　the　carboxylic　acid　function　of　ethylenediamine　tetra-acetic　acid　(EDTA)　molecules　together　can　be　taken　as　simple　model　for　the　amino　acids　components　of　proteins,　such　as　histones,　which　are　intimately　associated　with　the　DNA　of　eukaryotic　cells.　The　yield　of　single　strand　breaks　induced　by　10　eV　electrons　is　found　to　decrease　dramatically　as　a　function　of　the　number　of　organic　ions/nucleotide.　As　few　as　2　organic　ions/nucleotide　are　sufficient　to　decrease　the　yield　of　single　strand　breaks　by　70%.　This　effect　is　partly　explained　by　an　increase　in　multiple　inelastic　electrons　scattering　with　film　thickness　but　changes　in　the　resonance　parameters　can　also　contribute　to　DNA　protection.　This　can　occur　if　the　electron　captures　cross　section　and　the　lifetime　of　the　transient　anions　(i.e.,　core-excited　resonances)　formed　at　10　eV　are　reduced　by　the　presence　of　organic　ions　within　the　grooves　of　DNA.　Moreover,　it　is　proposed　that　the　tris　molecules　may　participate　in　the　repair　of　DNA　anions　[such　as　G　(-H)-]　induced　by　DEA　on　DNA　bases.　©　2010　American　Institute　of　Physics.