1. Experimental data of Shore, D. et. al. PNAS 1981, 78, (8), 4833-4837. a = 0

2. Gemmen, G. J.et. al. Nucleic Acids Res 2006, 34, (10), 2864- 77.

4. a = 15 nm

5. Eigenmodes for 100 nm long DNA loop with separation of 6 nm and end-angles held fixed First eigenmodeSecond eigenmode

6. Simulation techniques

7. Force ( p N ) Extension [nm] Spring constant (pN/nm) dk/dforce (1/nm) % 5251.1392.31603 15252.082.449291.3326 25253.0012.5050.5571 55255.5392.754370.8312 Linear DNA under force – Spring constant renormalization