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E lectric signals to reveal ion pump function

E lectric signals to reveal ion pump function. András Dér. Biological Research Center of the Hungarian Academy of Sciences Institute of Biophysics. P. O. B. 521, H-6701 Szeged, Hungary. Electric signals. Crucial role in life functions:. Signal and energy transduction. Signal transduction.

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E lectric signals to reveal ion pump function

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

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

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

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

  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. Microelectrode techniques fail for most pump proteins How to measure electric signals? 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 Suspension method(Keszthelyi and Ormos, 1980) Gel method (Dér et al., 1985) Dried samples(Nagy, 1978; Váró, 1983) Advantageous for kinetic experiments

  9. Bacteriorhodopsin

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

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

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

  21. Testing MD models Measurement Model

  22. The function of a bR molecule

  23. 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)

  24. 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

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