Calicheamicin being the most notable enediyne antitumor antibiotics derived from the bacterium Micromonospora echinospora. Calicheamicin targets DNA and cause strand scission. Calicheamicin binds with DNA in the minor groove, wherein they then undergo a reaction analogous to the Bergman cyclization to generate a diradical species. This diradical, 1,4-didehydrobenzene, then abstracts hydrogen atoms from the deoxyribose (sugar) backbone of DNA, which ultimately leads to strand scission. The specificity of binding of Calicheamicin to the minor groove of DNA was demonstrated to be due to the aryltetrasaccharide group of the molecule.