The larger retardation factor predicted from our jump model at these sites in DNA comes both from a larger excluded volume at these sites (ρ DN A T SEV /ρ RN A T SEV ∼ 1.5) and from a stronger initial Hbond (ρ DN A T SHB /ρ RN A T SHB ∼ 2), so that jumps to water acceptors are slowed down. In addition, jumps to nucleic acid acceptor sites (mainly N3(G)) also appear less favored in DNA then RNA. This can also be linked to the different double helical geometries, that position N3(G) a bit further from O2 in B-DNA than A-RNA (on average 4 vs 3.6 Å).