1. Lecture 2 Application of optical tweezers in single-molecule experiments with DNA DNA and RNA stretching experiments Entropic elasticity of a single DNA molecule A... T G... C C... G T... A. Nucleotides Adenine, Guanine, Cytosine, Tymine First experiment by Carlos Bustamante and co-workers Science (1992)

2. Optical Tweezers Mazolli, Maia Neto, and Nussenzveig, Proc. R. Soc. London, Ser. A 459, 3021 (2003) Viana, Rocha, Mesquita, Mazolli, Maia Neto, Nussenzveig, Appl. Phys. Lett. (2006) and PRE (2007) Neves, Fontes, Pozzo, Thomaz, Chilce, Rodriguez, Barbosa, Lenz-Cesar, Optics Express (2006) A. Ashkin, Phys. Rev. Lett. 24, 156 (1970) Recent theoretical and experimental advances

4. Visible He-Ne back-scattering profile

5. Marko-Siggia equation z= end-to-end distance A= persistence length L= contour length S. Harris et al. BJ 2005 (large scale MD, entropic effects, denaturing bubbles); G. Weber et al. Nature Phys., 2009 (microscopic elasticity). Force x extension curve

6. DNA/Ethidium Bromide Fit to the neighbor exclusion model

7. Ethidium bromideDaunomycin M. S. Rocha et al. JPC 2007

8. Psoralen

10. Circles: intercalated Squares: intercalated + UVA light Psoralen Márcio. S. Rocha, doctoral thesis UFMG (2008)

11. neighbor exclusion model Psoralen intercalated fraction Persistence length abrupt transition around r ~ 0.4

12. r = concentration of drug bound/concentration of DNA base-pairs r=0.4r=0.5 ab initio DFT calculation DNA/Psoralen

13. “DNA-psoralen: single-molecule experiments and first principles calculations” M. S. Rocha, A. D. Lúcio, S. S. Alexandre, R. W. Nunes, and O. N. Mesquita (APL, 2009)

15. Water transport in a single MDCK kidney cell How to measure the volume of a cell?

16. MDCK Kidney Cell Isoosmotic mediumHiperosmotic medium

17. Osmoregulation

18. Effect of vasopressin (AVP) on water transport Lucio, Santos, and Mesquita, PRE (2003)

19. Stretching DNA

20. Stretching RNA

25. The 3 Main Classes of Motor Proteins

29. DNA condensation

31. Fluctuation theorem PRL, 050601 (2002)

32. MORPHOLOGY-DEPENDENT RESONANCES (MDR) MODES

33. Blood 92, 2975 (1998)

34. PRL 93, 078102 (2004)

35. Acustooptical deflectors

39. Optical Tweezers is a very convenient tool to manipulate, apply and measure forces on single molecules (pN range). It can be used to measure and change transition states during protein folding, with access to the time evolution of these processes. It can be used for manipulating single cells for measurements of membrane elasticity, water transport and for manipulation of organelles inside the cell. It has been used as an interesting tool to test new ideas on Statistical Physics of small systems. It has been used for manipulation of nanowires, carbon nanotubes and silver nanoparticles. Applications of optical tweezers have increased much during the last few years.