as in enzyme-DNA complexes. [ 37 [[ http://en.wikipedia.org/wiki/Dna#cite_note-36 |]]] [ 38 [[ http://en.wikipedia.org/wiki/Dna#cite_note-37 |]]] Segments of DNA where the bases have been chemically modified by methylation may undergo a larger change in conformation and adopt the Z form . Here, the strands turn about the helical axis in a left-handed spiral,