Design Principles of Bacteriorhodopsin Imaging Systems Jussi Parkkinen Department of Computer Science University of Joensuu Finland

Co-authors Timo Jääskeläinen optics Sinikka Parkkinen molecular biology University of Joensuu Lasse Lensu information technology Lappeenranta University of Technology Michael Frydrych computational engineering Helsinki University of Technology

Outline Background Biological vision systems Basics of bacteriorhodopsin Design of bacteriorhodopsin based color vision system Conclusions

Outline Background Biological vision systems Basics of bacteriorhodopsin Design of bacteriorhodopsin based color vision system Conclusions

A description of spectral image formation

Visual pathway Detecting of the color signal – cones and rods Preprocessing in the retinal level – horizontal cells, amacrine cells, bipolar cells,... LGN level (6 layers) Visual cortex (10 8 cells) – other areas of cortex

Design of sensitivity function Sensitivity functions over spectrum – optimal functions – not realizable on molecular level Spectral band detectors – separate bands covering the spectrum – natural on molecular level

Artificial vision systems important Organic and biomolecules gaining interest in electronics Biological systems – object of research – source of innovations We study color vision systems and use biomolecules in a test system

Outline Background Biological vision systems Basics of bacteriorhodopsin Design of bacteriorhodopsin based color vision system Conclusions

Bacteriorhodopsin Membrane protein of Halobacterium salinarium Halobacterium salinarium lives in very salty waters Isolated by Oesterhelt and Stoeckenius in 1974

Why bacteriorhodopsin? photoelectric stable and long lifetime easy to produce possibility to modify the molecule > 10 6 reversible cycles Resolution > 5000 lines/mm

Bacteriorhodopsin applications Optical 3D memory Birge Optical recording media Hampp Optical sensor matrix Koyama et al. Color sensorParkkinen et al.

Outline Background Biological vision systems Basics of bacteriorhodopsin Design of bacteriorhodopsin based color vision system Conclusions

Preparation of BR/PVA-films Purple membrane was used 1. Mix Polyvinylalchohol (PVA) with BR-solution 2. Spread on a conductive glass 3. Let dry 24 hours 4. Sputter gold layer on the film to be the counter electrode

BR analogs used wild type BR 3,4-dehydro BR 4-keto BR

Outline Background Introduction to spectral color Biological vision systems Basics of bacteriorhodopsin Design of bacteriorhodopsin based color vision system Conclusions

–The photosensitivity of sensor is not very high –Differencies of timedelays between retinal analogs causes application dependend problems

Conclusions +Bacteriorhodopsin is a photoactive protein for color sensor +Protein based system is build, which learn it’s own color space +The detectors are easy to produce +Flexible shaped sensor possible +Color filter embedded in sensor

Acknowledgements Professor Dieter Oesterhelt for original BR Dr. Andrei Khodonov for retinal analogs Mr. Juha Juuti and Ms. Helvi Turkia for technical assistance The study was financially supported by Academy of Finland and TEKES/Finland