Department of Computer Science, University of Joensuu, P.O. Box 111, FIN-80101 Joensuu, Finland
Bacteriorhodopsin is a membrane protein of Halobacterium salinarium with a photochromic and photoelectric properties. There are number of applications proposed, where bacteriorhodopsin could be used. In our studies, we have evaluated ways to use bacteriorhodopsin as a photosensitive material for a color sensor. The closest resemblance for this kind of system is found in the human eye, where rhodopsin is the photoactive material.
As a starting point in design of color sensor, the color should be understood as color spectrum. From the spectrum, one has to define the wavelength region, which cover the range, visible to the sensor. The sensor is constructed from a number of detectors with different color sensitivity functions. Depending on the accuracy needs and material available, 2 to n sensitivity functions are needed. In bacteriorhodopsin the spectral sensitivity can be modified in two different ways, by modifying the protein part through mutation or by substituting the chromophore part by a retinal analog.
In our study, we used wild type bacteriorhodopsin and three bacteriorhodopsins where the chromophore was substituted by different retinal analogs. Bacteriorhodopsin was mixed in a polyvinylalchohol matrix and fixed between two electrodes on conducting glass. The color sensitivity properties of such a system were studied.