Figure 2.

Details of hydroxyl–radical interactions with the nucleosomal DNA. (A) Chemical reaction of hydroxyl-radicals with DNA backbone: deoxyribose hydrogen atoms (highlighted in gray) are abstracted leading to the destruction of deoxyribose residue and DNA cleavage. Only major phosphate-terminated cleavage products are shown. (B) A segment of nucleosome viewed from the top (see inset) in solvent accessible surface area (SASA) representation. Patches of SASA belonging to deoxyribose hydrogen atoms (H-SASA) are colored in gray. (C) The asymmetry of histone–DNA contacts with respect to the dyad axis location leads to its manifestation on DNA cleavage profiles. The dyad splits the segment of a DNA strand between the two adjacent binding sites into unequal parts with ∼3:7 ratio when counted in 5′-3′ direction.