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

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 (108 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

• > 106 reversible cycles

• Resolution > 5000 lines/mm

Bacteriorhodopsin applications

• Optical 3D memory Birge

• Optical recording media Hampp

• Optical sensor matrix Koyama et al.

• Color sensor Parkkinen 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

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