Fig. 1

Principle of RSE. a During the first step of RSE, the genomic template DNA (light blue) briefly gets denatured to allow capture primers (red) to hybridize. b The bound primers are enzymatically extended with biotinylated nucleotides. The extended portions of the primers, shown in green, form the “handle” to which streptavidin-coated magnetic beads bind. During this process many biotins of the same primer/target DNA complex are bound to streptavidin binding sites on the same bead, thereby forming a topological linkage that firmly locks even very long DNA segments extending in both directions from the capture point onto the surface of the magnetic bead. The primer/target DNA complex is then magnetically purified and released from the bead surface by heat. (The drawing is not to scale: the magnetic beads are approximately an order of magnitude larger than illustrated here)