Laura Innes Graduate Students: Eric Kalman, Matt Powell Prof. Zuzanna Siwy

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

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 pA

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

7. Why a Conical Pore? << Icone >> Icylinder d d L L D

8. Graph of Voltage Profile inside a Nanopore DV x x x

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

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

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

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

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

14. pH 6 -1000 mV -1000 mV no dendrimers

15. pH 8 -200 mV

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

17. pH 8 -1000 mV

18. pH 7 -300 mV

19. pH 7 -1000 mV

20. pH 7.5 -1000 mV

21. pH 7.5 Close up of -1000 mV

22. Lower Voltages • Force of Friction • 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. Is It a Single Dendrimer? -700 mV

26. pH 6 - 900 mv

27. pH 8 -900 mV