1. Electric signals to reveal ion pump function Biological Research Center of the Hungarian Academy of Sciences Institute of Biophysics P. O. B. 521, H-6701 Szeged, Hungary András Dér

2. Electric signals Crucial role in life functions: Signal and energy transduction

3. Nobel prize (1963) Hodgkin, Huxley, Katz Signal transduction Propagation of the nerve impulse

4. chemiosmosis: P. Mitchell, Nobel prize, 1978 ATP-ase: Boyer, Walker, Skou, Nobel prize, 1997 mitochondrial electron transfer Energy transduction

5. Why should we measure electric signals? Direct information about kinetics, ion specificity Together with other methods: details of the molecular mechanism is expected to be revealed Physicist's approach: atomic level description - chance to design molecules for biotechnology

6. How to measure electric signals? Microelectrode techniques fail for most pump proteins Patch clamp; Nobel prize 1991: Neher and Sackmann Alternative methods. Prerequisite: electrically asymmetric sample

7. 1. Surface methods BLM method (Dancsházy et al., 1976; Bamberg et al., 1980) SSM method (Fendler et al., 1992) Advantage: ion specificity Disadvantage: limited spatio-temporal information

8. 2. Bulk methods Advantageous for kinetic experiments Suspension method (Keszthelyi and Ormos, 1980) Gel method (Dér et al., 1985) Dried samples (Nagy, 1978; Váró, 1983)

9. Bacteriorhodopsin

10. bR plays a model role among ion- transporting membrane proteins stability, absorption changes, photoelectric effects

11. polarizer exciting laser sample detector transient recorder computer trigger input 1 input 2 amplifier electrodes detectormonochromator cont. light source (mirror) Gel method

12. Correlation between electric and optical signals

13. Conditions: speed, linearity, insensitivity to geometric details

14. Modeling the electrolyte

15. Ionic relaxation

16. Properties of ionic relaxation 1. speed 2. anisotropy (F) 3. linearity (E) 4. insensitivity to geometric details (B,C,D)

17. Temporal superposition solved

18. How can we use this?

19. … …

21. Detection of the 3D electric signals Dér et al. (1999)

22. MeasurementModel Testing MD models

24. The function of a bR molecule

25. Further application examples of the bulk methods Cl - pumping (halorhodopsin, bacteriorhodopsin) Signal transduction (Chlamydomonas rhodopsin, squid rhodopsin) Primary processes of photosynthesis (plant and bacterial photosynthetic reaction centers) Bioelectronics - fast photodiode, motion sensitive camera (bacteriorhodospin)

26. Acknowledgements Lajos Keszthelyi Pál Ormos György Váró Rudolf Tóth-Boconádi László Oroszi László Fábián Szeged Stefka Taneva Sofia Sándor Suhai Nicoleta Bondar Heidelberg Walther Stoeckenius San Francisco