Photoreceptor blue light

Amorphous (vitreous) selenium, vacuum-deposited on an aluminum substrate such as a dmm or a plate, was the first photoconductor commercially used in xerography (6). It is highly photosensitive, but only to blue light (2). Its light absorption falls off rather rapidly above 550 nm. Because of the lack of photoresponse in the red or near infrared regions, selenium photoreceptors caimot be used in laser printers having He—Ne lasers (632.8 nm), or soHd-state lasers (680—830 nm). 

Partch, C. L. et al., Postranslational regulation of mammalian circadian clock by cryptochrome and proteinphosphatase 5, Proc Aarf Acad. Sci. USA, 103, 10467, 2006. Briggs, W.R., Christie, J.M., and Salomon, M., Phototropins a new family of flavinbinding blue light receptors in plants, Antioxid. Redox Signal, 3, 775, 2001. Briggs,W.R. et al.. The phototropin family of photoreceptors. Plant Cell, 13, 993, 2001. 

Jung, A., J. Reinstein, T. Domratcheva, R. L. Shoeman, and I. Schlichting (2006). Crystal structures of the AppA BLUF domain photoreceptor provide insights into blue light-mediated signal transduction. J Mol Biol 362 717-732. 

To date, analyses of the Phycomyces light responses have remained at a rather formal level whereas the ultimate goal must be a detailed description of the chemical steps in reception, transmission and reaction to the stimulus of light. The first of these steps is excitation of the photoreceptor by light and it is therefore not unexpected that many attemps have been made to identify and isolate this compound. In spite of much effort during the past years, not only wi th Phycomyces, the blue light photo-... 

Among the many sensory reactions Phycomyces displays, the study of the photoreceptor and adaptation deserves maximal attention, since Phycomyces shares these two attributes with a variety of other blue light sensitive organisms. Action-spectroscopy indicates a flavin as the photoreceptor of Phycomyces. /3-carotene was positively ruled out as a possible receptor, since mutants with no trace amounts of )3-carotene are phototropical normal. The photoreceptor has not yet been isolated. As in other systems the difficulty consists in distinguishing the flavin photoreceptor from the bulk flavoproteins in the cell. One therefore needs unambiguous criteria for the identification of the photoreceptor. The most promising approach for an isolation would be a photoreceptor mutant and we described the properties those mutants should have. Until now there is no firm evidence that the photomutants, madA or madB are defective in the photoreceptor. 

Using blue-light photoreceptors from Bacillus subtilis and Pseudomonas putida that contain light-oxygen-voltage sensing domains, flavin mononucleotide-based fluorescent proteins were produced that can be used as fluorescent reporters in both aerobic and anaerobic biological systems. 

Bridges C 1959 The visual pigments of some common laboratory animals. Nature 184 727-728 Burns ME, Baylor DA 2001 Activation, deactivation, and adaptation in vertebrate photoreceptor cells. Annu Rev Neurosci 24 779-805 Cashmore AR, Jarillo JA, Wu Y-J, Liu D 1999 Cryptochromes blue light receptors for plants and animals. Science 284 760-765... 

Shalitin D, Yang H, Mockler TC et al 2002 Regulation of A rahidopsis cryptochrome 2 by blue-light-dependent phosphorylation. Nature 417 763—767 Stanewsky R, Kaneko M, Emery P et al 1998 The cryb mutation identifies cryptochrome as a circadian photoreceptor in Drosophila. Cell 95 681-692 Takahashi JS, DeCoursey PJ, Bauman L, Menaker M 1984 Spectral sensitivity of a novel photoreceptive system mediating entrainment of mammalian circadian rhythms. Nature 308 186-188... 

Thresher RJ, Vitatema MH, Miyamoto Y et al 1998 Role of mouse cryptochrome blue-light photoreceptor in circadian photoresponses. Science 282 1490-1494... 

Egan ES, Franklin TM, Hilderbrand-Chae MJ et al 1999 An extraretinally expressed insect cryptochrome with similarity to the blue light photoreceptors of mammals and plants. J Neurosci 19 3665-3673... 

If blue light is used for the discharge process, then the absorption is very close to the charged surface, and one can assume that the discharge process involves the transport of photogenerated holes through the bulk. Trapping of these holes in the bulk then results in the observed first residual potential Vri. In the case of amorphous selenium photoreceptor films, it has been found that Ki is predicted by the Waiter expression [16]... 

From such a viewpoint, we are examining primary processes of photoreactions of PYP [1] which functions as a blue light photoreceptor for a negative phototaxis of the purple sulfur bacterium Ectothiorhodospira halophila, some FP s [2] and Rh [3] by means of the fs fluorescence up-conversion measurements. In this article, we will discuss our latest results of fs fluorescence dynamics studies on PYP, because PYP is very stable for repeated irradiation which induces photocycles so that the very accurate experimental results can be obtained rather easily and also the preparation of the site-directed mutants as well as the PYP analogues with modified chromophores are rather easy. However, before that, we will summarize briefly results of our previous investigations. 

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