1. Laura Innes Graduate Students: Eric Kalman, Matt Powell Prof. Zuzanna Siwy Department of Physics and Astronomy University of California, Irvine Looking at Single Molecules with Nanopores

2. Why are Nanopores Interesting? Biological channels are the basis of many physiological processes e.g. heart and muscle function and ‘wiring’ information from the brain to all the cells. Nanopores are the basis for biosensors detecting single molecules http://www1.engr.ucsb.edu/~saleh/Research/Saleh_Omar_Thesis. pdf http://en.wikipedia.org/wiki/Cell_membrane

3. Making Nanopores Creation of single nanopores starts at the GSI accelerator center in Darmstadt, Germany Irradiated with a single ion of Au or U, at 2 GeV (15% c) Deposition of energy from the swift, heavy ion creates a damage track in polymer Chemical etching – ‘developing’ of the track created by single heavy ions

4. Equipment Conductivity Cell Faraday Cage

5. Etching Current 1000 mV pA

6. Gold Replica of a Single Nanopore Scopece et al. Nanotechnology 17 (2006) 3951. Formulas R – ionic resistance of a nanopore  - specific conductivity of electrolyte L – membrane thickness D d

7. Why a Conical Pore? L L d d D I cone >> I cylinder <<

8. Graph of Voltage Profile inside a Nanopore x x x VV

9. Structure of Dendrimers ~3 nm http://www.fda.gov/NANOTECHNOLOGY/powerpoint_conversions/chbsa-nanotech-presentation06- 05_files/images/image4.png H+H+ H+H+

10. Basic Physical Chemistry of a Charged Particle in a Solution ƒ F ΔV - potential difference between two electrodes l - distance apart ƒ - frictional force u - mobility of the ion ze - charge s - drift speed When 2 a

11. I U 1.0 M KCl Dendrimer Detecting Dendrimers current time

12. Dendrimers at Various pH’s pH 6 pH 8 pH 7 pH 10

13. pH 10 - 1000 mV KCl + dendrimers KCl without dendrimers

14. pH 6 -1000 mV no dendrimers

15. pH 8 -200 mV

16. -800 mV pH 8 Occasional openings Blockage of the pore

17. -1000 mV pH 8

18. pH 7 -300 mV

19. -1000 mV pH 7

20. pH 7.5 -1000 mV

21. Close up of -1000 mV pH 7.5

22. Lower Voltages 1.Force of Friction 2.Entropy ƒ F

23. There is a Voltage Threshold for the Dendrimers to Enter a Nanopore -100 mV -1000 mV

24. Future Studies current time Continue to study the behavior of single molecules and nanopores Hopefully create an electromechanical valve

25. -700 mV Is It a Single Dendrimer?

26. - 900 mv pH 6

27. -900 mV pH 8