Photosensitive proteins

A recent study has focused on structural and electronic aspects of a bacteriochlorophyl derivative (methyl bacteriophorbide) in the crystal phase [45]. The calculations are in good agreement with experimental data and provide evidence of a local structural change upon electronic excitation. 

AIMD simulations have also been carried out on the chromophore present in the rhodopsin photoreceptor (retinal). In the primary event of vision, retinal passes from the ground state (GS) to an excited state (ES) and isomerizes from 11-cis to all-trans within 200 fs. A series of papers [46-50] have analyzed the GS isomerization process. More recently, calculations were extended to the first singlet ES [51] within a recently developed scheme for singlet state dynamics [52]. This work characterizes structural and energetic changes during the photoisomerization process and points to the crucial role of environment effects. 

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Given the actual scenario, one can state that the emerging field of nanotechnology represents new effort to exploit new materials as well as new technologies in the development of efficient and low-cost solar cells. In fact, the technological capabilities to manipulate matter under controlled conditions in order to assemble complex supramolecular structures within the range of 100 nm could lead to innovative devices (nano-devices) based on unconventional photovoltaic materials, namely, conducting polymers, fuUerenes, biopolymers (photosensitive proteins), and related composites. 

Keywords Drug delivery Gene therapy Macromolecule Peptide nucleic acid Photochemical internalization Photodynamic Photosensitizer Protein toxin siRNA... 

The relative complexity of the proton transfer mechanism in bR or other photosensitive proteins explain why the mechanism of photosynthesis in plants is much less understood than that performed by H. salinarum, a bacterium that is much less familiar than green leaves. 

Maksimov EG, Gostev TS, Kuz minov FI, Sluchanko NN, Stadnichuk IN, Pashchenko VZ, Rubin AB (2010) Hybrid systems of quantum dots mixed with the photosensitive protein phycoerythrin. Nanotechnol Russia 5(7-8) 531... 

Encinas, S., Miranda, M. A., Marconi, G., and Monti, S., Transient species in the photochemistry of tiaprofenic acid and its decarboxylated photoproduct, Photochem. Photobiol, 68, 633, 1998. Miranda, M. A., CasteU, J. V., Hernandez, D., Gomez-Lechon, M. J., Bosca, E, Morera I. M., and Sarabia, Z., Drug-photosensitized protein modification identification of the reactive sites and elucidation of the reaction mechanism with tiaprofenic acid/albumin as a model, Chem. Res. Toxicol, 11, 172,1998. 

Vsevolodov, N.N., Biomolecular Electronics. An Introduction via Photosensitive Proteins, Birkhauser, Boston, MA, 1998. 

Vsevolodov, N., Biomolecular Electronics An Introduction via Photosensitive Proteins, Birkhauser, Boston, MA, 1998 Stuart, A. et al, Proc. IEEE Nonvol. Mem. Tech. (INVMTC), 6, 45-51,1996. 

Dichromated Resists. The first compositions widely used as photoresists combine a photosensitive dichromate salt (usually ammonium dichromate) with a water-soluble polymer of biologic origin such as gelatin, egg albumin (proteins), or gum arabic (a starch). Later, synthetic polymers such as poly(vinyl alcohol) also were used (11,12). Irradiation with uv light (X in the range of 360—380 nm using, for example, a carbon arc lamp) leads to photoinitiated oxidation of the polymer and reduction of dichromate to Ct(III). The photoinduced chemistry renders exposed areas insoluble in aqueous developing solutions. The photochemical mechanism of dichromate sensitization of PVA (summarized in Fig. 3) has been studied in detail (13). 

Puromycin. Puromycin (19), elaborated by S. alboniger (1—4), inhibits protein synthesis by replacing aminoacyl-tRNA at the A-site of peptidyltransferase (48,49). Photosensitive analogues of (19) have been used to label the A-site proteins of peptidyltransferase and tRNA (30). Compound (19), and its carbocycHc analogue have been used to study the accumulation of glycoprotein-derived free sialooligosaccharides, accumulation of mRNA, methylase activity, enzyme transport, rat embryo development, the acceptor site of human placental 80S ribosomes, and gene expression in mammalian cells (51—60). 

In addition, Montenegro et al., (2007) determined that the photosensitized RF-mediated degradation of vitamins A, D3, and RF itself in skimmed milk was strongly reduced by the addition of small amounts of lycopene-gum arabic-sucrose microcapsules, prepared by spray-drying. Under these conditions, the bulk properties of the skimmed milk were unmodified. The main photoprotection mechanism of the milk vitamins was the efficient quenching of the 3Rf by the protein moiety of GA. Small contributions (<5%) to the total photoprotection percentage was due to both inner filter effect and 1O2 quenching by the microencapsulated lycopene. 

In plants, the photosynthesis reaction takes place in specialized organelles termed chloroplasts. The chloroplasts are bounded in a two-membrane envelope with an additional third internal membrane called thylakoid membrane. This thylakoid membrane is a highly folded structure, which encloses a distinct compartment called thylakoid lumen. The chlorophyll found in chloroplasts is bound to the protein in the thylakoid membrane. The major photosensitive molecules in plants are the chlorophylls chlorophyll a and chlorophyll b. They are coupled through electron transfer chains to other molecules that act as electron carriers. Structures of chlorophyll a, chlorophyll b, and pheophytin a are shown in Figure 7.9. 

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