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

2. Single Molecule: Detection and Manipulation Tools: Optical Tweezers Confocal fluorescence microscopy Evanescent illumination Molecular biology techniques (Ensemble (10 18 ) Single molecule (10 0 Averages Dynamics, Individual behavior

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

4. Pulling on a DNA molecule with Optical Tweezers Bead

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

6. 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) Single Molecule: Detection and Manipulation

7. Transcription Regulation by looping of DNA DNA

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

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

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

11. Evanescent Illumination Bead Bead Microscope Objective

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.