Fig. 1From: Middle-down electron capture dissociation and electron transfer dissociation for histone analysis a Histone lysine side chains can be acetylated via histone acetylases and deacetylated via histone deacetylases. The acetylation creates a newly formed amide bond that cannot be protonated. b Thus, acetylated histones cannot interact closely with negatively charged DNA, opening up chromatins to their active formBack to article page