Photosensory transduction

If flavin triplet excitation were involved in photosensory transduction of an organism, then substances that quench this excited state, and thus compete with the normal transduction sequence, should selectively inhibit photomovement in this organism. On the other hand, no effect on such an agent would be expected if the chromophore were a carotenoid. 

The different steps involved in the photosensory transduction chain of microorganisms have been investigated in recent years by several research groups, but many problems are still not clarified. It is generally accepted that the components of a stimulus-response system can be schematized as follows ... 

Fabczak, S., Fabczak, H., Xao, N., and Song, P-S., Photosensory transduction in ciliates I. An analysis of light-induced electrical and motile responses in Stentor coeruleus, Photochem. Photobiol, 57, 696, 1993. 

FIGURE 120.4 The photosensory transduction chain in photomotile microorganisms. 

Photosensory Transduction Chain Photoreceptor Pigments Dark Reactions Steps in the Sensory Transduction Chain 122-7... 

To summarize, these results could suggest that the photosensory transduction chain in these ciliates is similar to that of vertebrates. 

Foster I don t want to discuss the details of the experiments, but it is possible to show that a bleachable pigment isn t sufficient. You can get this with RGR. What you have to show is that this pigment can activate a transduction cascade in some way. This is the way to tease apart the photoisomerase as distinct from the photosensory molecule. 

Table 2 summarizes different possible applications of photoswitchable biomaterials, while detailing the nature of the biomaterial, the area of application, and, when possible, specific examples. Reversible light-induced activation and deactivation of redox proteins (enzymes) corresponds to write - read - erase functions. The photonic activation of the biomaterial corresponds to the write function, whereas the amperometric transduction of the recorded optical information represents the read function of the systems. Switching off of the redox functions of the proteins erases the stored photonic information and regenerates the photosensory biomaterial. These integrated, photoswitchable redox enzyme electrode assemblies mimic logic functions of computers, and may be considered as first step into the era of biocomputers. 

Lipson, E.D. and Horwitz, B.A., Photosensory reception and transduction, in Sensory Receptors and Signal Transduction, Spudich, J. and Satir, B., Academic Press, New York, 1991, p. 1. 

Quail, P.H. et al. Phytochromes photosensory perception and signal transduction, Science, 268, 675, 1995. 

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