The 601 nucleosome positioning sequence is shown in green (601* represents the introduction of 2 nt gaps at nucleotides 53 and 54 in the top and bottom strands of the 601 positioning sequence, respectively). For mononucleosome DNA constructs, the ssDNA spacer used to circumvent surface effects in single-molecule FRET measurements is underlined. Constructs referred to as ‘mononucleosome [or dinucleosome] with n bp linker DNA’ were used in single-molecule and bulk remodelling experiments. For ensemble remodelling experiments with mononucleosomes, the ssDNA spacer was omitted without any appreciable change in the overall remodelling kinetics. Constructs referred to as ‘symmetric mononucleosomes with n bp linker DNA’ were used in crosslinking experiments. Asymmetric constructs with the same linker length on one side of the nucleosome but only 3 bp of linker DNA on the other side displayed quantitatively similar crosslinking behaviour.