1. Kirchhoff-Institut für Physik Molekulare Biophysik (F15) Gerrit L. Heuvelman Atomic Force Microscope

2. Scanning Probe Microscopy STM: scanning tunneling microscope AFM: atomic force microscope MFM: magnetic force microscope SNOM: scanning near-field optical microscope y x tunneling of electrons between probe and surface measuring of the force on the probe AFM with magnetical probe probe is a fiber; tunneling of fotonen

3. STM: scanning tunneling microscope nA R piezo- element e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- < 1nm tunneling of electrons through air between probe and surface only conducting material probe x-y stage

4. STM: scanning tunneling microscope nA I control I tip ∆I R ∆I -> ∆V transfer piezo-element (changes length at different voltages)

5. AFM: atomic force microscope AFM probe scans over the surface (in contact) e.g. living cells, chromatin fibers laser photodiode piezo-element probe SFM: scanning force microscope

6. MFM: magnetic force microscope AFM with magnetic probe e.g. hard disc, tape magnetic tip laser photodiode piezo-element

7. SNOM: scanning near-field optical microscope fiber tunneling of photons between probe and surface shows the amount of light that is absorbed/transmitted for different colors sample lens detector filter e.g. fluorescent molecules metal-coated fiber tip

8. Atomic Force Microscope cantilever tip laser cantilever piezo y z x photodiode

9. tipholder motor control SPM tip sample piezo translator laser beam mirror photodiode sample x,y,z piezo translator fluid influid out fluid cell O-ring Atomic Force Microscope in air and in buffer solutions

10. path of AFM tip AFM tip superhelical DNA plasmid DNA double helix Mg 2+ negatively charged mica surface Mg 2+ movement of the AFM tip along the sample

11. AFM image of a 6.8 kb superhelical plasmid AFM tip

12. AFM image of a nucleosome on a 614 base pair DNA 2 µm x 2 µm overview scan zoom of mononucleosome complexes Kepert, F., Fejes Tóth, K., Caudron, M., Mücke, N., Langowski, J. & Rippe, K., manuscript in preparation

13. AFM image of a nucleosome on a 614 base pair DNA 2 µm x 2 µm overview scan zoom of mononucleosome complexes Kepert, F., Fejes Tóth, K., Caudron, M., Mücke, N., Langowski, J. & Rippe, K., manuscript in preparation

14. DNA entry-exit angle of nucleosomes

15. movement of a 600 bp DNA fragment by AFM

16. different levels of chromatin packing A C D E F B 300 nm 700 nm 11 nm 30 nm 2 nm 1400 nm 2 nm 11 nm 30 nm 300 nm 700 nm 1400 nm

17. chromatin structure 400 nm x 400 nm

18. chromatin structure 400 nm x 400 nm

19. chromatin structure

20. spectrin C-terminal Helix C N-terminal Helix B Helix A molecule that contributes to the mechanical properties, especially the elasticity of the cells measurement of its mechanical stability provides information about the physiological function

21. stretching spectrin with an AFM distance force 123 surface cantilever tip 4 repeated spectrin domain 1. adhesion force between cantilever tip and surface 2. dissociation from the folded state to the intermediate unfolded state 3. dissociation from the intermediate to the total unfolding state

22. 0.15 1003040 0.05 2050 0.10 0.20 0.00 unfolding force (pN) probability stretching spectrin with an AFM force (pN) 020406080 0 40 20 60 80 100 distance (nm) -20