High-Density Labeling of DNA: Preparation and Characterization of the Target Material for Single-Molecule Sequencing The authors are grateful to Dr. Dmitri Czerny of the Max Planck Institute for Biophysical Chemistry, Göttingen, for generating the electron micrograph. Our work was supported by the Max-Planck-Gesellschaft, the BMBF together with Roche Diagnostics (grant no.: 0311003), and the Deutsche Forschungsgemeinschaft (grant no.: Ei 411/1-1).