1. Joel Stavans’ group: Single Molecule: Detection and Manipulation Jaffar Ali Ido Braslavsky Roee Amit • Interaction Between • Membranes and Polymers Ilan Tsafrir Tamar Arzi Physics of Complex Systems - Weizmann Institute of Science

2. Single Molecule: Detection and Manipulation (Ensemble (1018) <=> Single molecule (100 Averages <=> Dynamics, Individual behavior Tools: • Optical Tweezers • Confocal fluorescence microscopy • Evanescent illumination • Molecular biology techniques

3. Infrared Light Bead Bead Microscope Objective Optical Tweezers Force (pN) Small particles (micron scale) can be trapped by the intensity gradient of focused light F=-a(E)2 Noninvasive Techniques in Cell Biology: 375 (1990)

4. Pulling on a DNA moleculewith Optical Tweezers Bead

5.  DNA : Force - Extension Curve Approximation of the Worm-like Chain Model prediction:

6. Single Molecule: Detection and Manipulation • Looping of DNA Opher Gileadi (Weizmann, Molecular Genetics) Stephen Quake (Applied Physics, Caltech) • Collapse of DNA Stephen Quake • Single Molecule Enzymatic Activity David Bensimon (ENS, Physics)

7. Transcription Regulation by looping of DNA DNA

8. Enhancer site P(L) L Science 233:889(1986) TIBS 20:500 (1995) Looping of DNA Spontaneous Gelles, Science 267:378 (1995) Looping dynamics: Time scales of bound and unbound states Dependence on length Dependence on Persistence length

9. Asymmetric Protein Induced Looping - influence of bending protein IHF IHF

10. IHF - Integrating Host Factor This protein induces a U-Turn in DNA IHF - blue/red DNA - green/yellow

11. Evanescent Illumination Microscope Objective Bead Bead

12. Summary: • Macromolecules are interesting as a complex physical system while understanding their physical properties could contribute to the understanding of their function as a biological ingredient. • The experimental tools enable us to monitor and manipulate single molecules.