Biological photoreceptors

Such an ordered organization of biological photoreceptor molecules appears to be a common feature (which, of course, is hardly detected in more opaque, highly scattering biological material). In the vertebrate rod maximum absorption lies in membranes (discs) perpendicular to the long axis of the rods, but anisotropically within these planes47). 

Lately, the CP-MD approach has been combined with a mixed QM/MM scheme [10-12] which enables the treatment of chemical reactions in biological systems comprising tens of thousands of atoms [11, 26]. Furthermore, CP-MD and mixed QM/MM CP-MD simulations have also been extended to the treatment of excited states within a restricted open-shell Kohn-Sham approach [16, 17, 27] or within a linear response formulation of TDDFT [16, 18], enabling the study of biological photoreceptors [28] and the in situ design of optimal fluorescence probes with tailored optical properties [32]. Among the latest extensions of this method are also the calculation of NMR chemical shifts [14]. 

Photochromism was first described in the scientific literature in 1876. 7 In his famous paper entitled The Photochemistry of the Future (1912), G. Ciamician19 discussed the importance of photochromic substances and mentioned the possibility of using such compounds for fashion purposes. Photochromism is also a natural phenomenon most biologic photoreceptors exhibit photochromic behavior. 101 Until the middle of this century research on photochromic compounds was mainly carried out in academic centers, but around 1960 it was recognized that this subject is also of considerable commercial interest and since then most of the research has been done in industrial laboratories. The applications of photochromic materials can been classified as follows 7 ... 

M., Hildebrandt, P., and Murgida, D.H. (2006) Time-resolved methods in biophysics. 1. A novel pump and probe surface-enhanced resonance Raman approach for smdying biological photoreceptors. Photochemical cf Photobiological Sciences, 5,1103-1108. 

PA and PT phenomena are widely used for numerous non-spectroscopic applications such as the determination of thermal diffusivity, non-destructive testing of materials (in particular the probing of sub-surface defects) by thermal wave imaging, time-resolved studies of de-excitation processes or on biological photoreceptors, studies of phase transitions, etc. Here, only spectroscopic applications are considered that demonstrate the main characteristics and the potential of photoacoustic spectroscopy (PAS). In the following, illustrative examples are presented for solids, liquids, gases, biological and medical samples. 

The basic principle in the molecular mechanism of biological photoreceptors appears to be the interaction between a photochromic moiety and a macromolecule. The protein-ligand complex as a whole is known to be embedded in a membrane matrix. In a very general way the results of our studies can be summarized by stating that in photochemical energy transductions both features are very important. That is, the... 

To induce immune suppression the electromagnetic energy of UV radiation must first be absorbed by an epidermal photoreceptor and then converted into a biologically recognizable signal. Three epidermal photoreceptors have been identified DNA, urocanic acid (UCA) and membrane lipids. 

UV-irradiated cells. Using cell-free cytosolic keratinocyte extracts, Simon and colleagues26 confirmed the role of membrane oxidation in NF-kB activation. Particularly important aspects of the experimental design employed by Simon and colleagues was the use of keratinocytes versus cells derived from a cervical cancer patient, and the use of biologically relevant UVB (290 to 320 nm) radiation versus UVC (200 to 290 nm) radiation, which is filtered out by the atmospheric ozone layer and does not reach the earth s surface. Overall, these data indicate that the activation of cytokine transcription, a step essential for the induction of immune suppression, can occur independently of UV-induced DNA damage and suggest that membrane lipid oxidation can serve as a UV 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. 

Hubbell, W.L., 1990, Transbhayer couphng mechanism for the formation ofhpid asymmetry in biological membranes. Application to the photoreceptor disc membrane. Biophys. J. 57 ... 

Although Chi, as well as most of biological pigments isolated from living organisms, is unstable under ambient conditions, the usefulness of Chi as a photoreceptor in in vitro studies is important for the following reasons ... 

Our retina has red, green, and blue cones which include rhodopsins as photoreceptors [6-8], Phytochromes are photo-sensors of green plants [9], Biological luminescences from fireflies [10] and some jellyfishes [11] are also beautiful activities of living organism. Recently, fluorescent proteins are routinely applied as molecular markers for gene expression in the field of molecular biology [12]. 

Post-ingestion from a-, (3- y-carotene other carotenes from plant leaves a wide variety of fruit, root seed sources e.g. Daucus carota (carrot) (Apiaceae) [root] Retinal covalently linked to opsins (— light receptor Rhodopsins in vision) colour blind John Dalton (atomic theory, 1766-1844) bequeathed his eyes to science 2 centuries on molecular biology confirmed the absence of the gene for the green photoreceptor opsin... 

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