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