Photoisomerization retinal

Dioumaev, A. K., Brown, L. S., Needleman, R., and Lanyi, J. K. (1998). Partitioning of free energy gain between the photoisomerized retinal and the protein in bacteriorhodopsin. Biochemistry 37, 9889-9893. 

These chemicaUy different chromophores undergo different, early, light-induced molecular transformations photoinduced charge transfer (flavins, stentorin, and blepharismins), cis-trans photoisomerization (retinals, 4-hydroxy-cinnamic acid), and energy transfer (pterins-ffavins). 

The first study in which a full CASSCE treatment was used for the non-adiabatic dynamics of a polyatomic system was a study on a model of the retinal chromophore [86]. The cis-trans photoisomerization of retinal is the primary event in vision, but despite much study the mechanism for this process is still unclear. The minimal model for retinal is l-cis-CjH NHj, which had been studied in an earlier quantum chemisti7 study [230]. There, it had been established that a conical intersection exists between the Si and So states with the cis-trans defining torsion angle at approximately a = 80° (cis is at 0°). Two... 

Nonadiabatic transitions definitely play crucial roles for molecules to manifest various functions. The theory of nonadiabatic transition is very helpful not only to comprehend the mechanisms, but also to design new molecular functions and enhance their efficiencies. The photochromism that is expected to be applicable to molecular switches and memories is a good example [130]. Photoisomerization of retinal is well known to be a basic mechanism of vision. In these processes, the NT type of nonadiabatic transitions play essential roles. There must be many other similar examples. Utilization of the complete reflection phenomenon can also be another candidate, as discussed in Section V.C. In this section, the following two examples are cosidered (1) photochromism due to photoisomerization between cyclohexadiene (CHD) and hexatriene (HT) as an example of photoswitching molecular functions, and (2) hydrogen transmission through a five-membered carbon ring. 

Garavelli M, Gelani P, Bernardi F, Robb MA, Olivucci M (1997) The CyHgNH protonated shiff base an ab initio minimal model for retinal photoisomerization. J Am Chem Soc 119 6891... 

Migani A, Sinicropi A, Ferr N, Cembran A, Garavelli M, Olivucci M (2004) Structure of the intersection space associated with Z/E photoisomerization of retinal in rhodopsin proteins. Faraday discuss 127 179... 

BR from H. salinarum is a light-driven proton pump, which is triggered by the photoisomerization of retinal covalently linked to its Lys216. It consists of a single polypeptide of 248 amino-acid residues, including seven a-helical TM chains A-G and interconnecting loops, as schematically illustrated in Figure 23. BR is one of the most intensively studied membrane proteins. A variety of experimental techniques have shown it to be... 

The CP MAS NMR spectroscopy has been also extensively used for studies of proteins containing retinylidene chromophore like proteorhodopsin or bacteriorhodopsin. Bacteriorhodopsin is a protein component of purple membrane of Halobacterium salinarium.71 7 This protein contains 248 amino acids residues, forming a 7-helix bundle and a retinal chromophore covalently bound to Lys-216 via a Schiff base linkage. It is a light-driven proton pump that translocates protons from the inside to the outside of the cell. After photoisomerization of retinal, the reaction cycle is described by several intermediate states (J, K, L, M, N, O). Between L and M intermediate states, a proton transfer takes place from the protonated Schiff base to the anionic Asp85 at the central part of the protein. In the M and/or N intermediate states, the global conformational changes of the protein backbone take place. 

The vibronic coupling model has been applied to a number of molecular systems, and used to evaluate the behavior of wavepackets over coupled surfaces [191]. Recent examples are the radical cation of allene [192,193], and benzene [194] (for further examples see references cited therein). It has also been used to explain the lack of structure in the S2 band of the pyrazine absorption spectrum [109,173,174,195], and recently to study the photoisomerization of retinal [196],... 

Dienes and polyenes have been a subject of great interest due to their important role in biology, materials science and organic synthesis. The mechanism of vision involves cis-trans photoisomerization of 11 -civ-retinal, an aldehyde formed from a linear polyene. Moreover, this kind of molecule exhibits high linear and non-linear electrical and optical properties. Short polyenes are also involved in pericyclic reactions, one of the most important classes of organic reactions. 

Shichi, H. and Somers, R. L. Possible involvement of reti-nyhdene phospholipids in photoisomerization of all-frans to 11-cis retinal. /. Biol. Chem. 249 6570-6577,1974. 

The evidence to-date shows that vertebrate photoreception is mediated by a closely related group of proteins termed opsins. These are G protein-coupled receptors characterized by their ability to bind a vitamin A based chromophore ( -cis-retinal) via a Schiff base linkage using a lysine residue in the 7th transmembrane a helix (Fig. 1). The primary events of image detection by the rods and cones occurs with the absorption of a photon of light by ll-r/r-retinal and its photoisomerization to the AUtrans state (Bums Baylor 2001, Menon et al 2001). Although photoreception is best understood in retinal rods and cones, photoreception is not confined to these structures. In non-mammalian... 

In such a way we were able to conclude that the illumination of suspensions of photoreceptor outer segments by 450 nm light at 77°K, which was known to result in the rhodopsin— prelumirhodopsin transition (corresponding to 11-cis-retinal— transretinal photoisomerization of chromophore), leads also to the appearance of some reduction centers and to the conformational change of membrane. 

Retinol A. can be enzymically formed from retinoic acid. B. is transported from the intestine to the liver in chylomicrons. C. is the light-absorbing portion of rhodopsin. D. is phosphorylated and dephosphorylated during the visual cycle. E. mediates most of the actions of the retinoids. Correct answer = B. Retinyf esters are incorporated into chylomicrons. Retinoic acid cannot be reduced to retinol. Retinal, the aldehyde form of retinol, is the chromophore for rhodopsin. Retinal is photoisomerized during the visual cycle. Retinoic acid, not retinol, is the most important retinoid. 

M. Garavelli, T. Vreven, P. Celani, F. Bernardi, M. A. Robb, and M. Olivucci,/. Am. Chem. Soc., 120, 1285 (1998). Photoisomerization Path for a Realistic Retinal Chromophore Model The Nonatetraeniminium Cation. 

K. A. Freedman and R. S. Becker, /. Am. Chem. Soc., 108, 1245 (1986). Comparative Investigation of the Photoisomerization of the Protonated and Unprotonated Normal-Butylamine Schiff-Bases of 9-cis-Retinals, 11-ds-Retinals, 13-cis-Retinals, and all-trans-Retinals. 

Takahashi T et al (1991) Photoisomerization of retinal at 13-ene is important for phototaxis of Chlamydomonas reinhardtii - simultaneous measurements of phototactic and photophobic responses. Biochem Biophys Res Com 178 1273-1279... 

Bacteriorhodopsin (bR) is a transmembrane protein located in the cell membrane of purple bacteria and contains in its ground state an all-trans retinal chromophore that absorbs at 570 nm. After illumination, the chromophore isomerizes, and a proton is pumped in five consecutive steps from the cytoplasm to the extracellular side of the membrane. The resulting pH gradient is then used to synthesize ATP. In the first proton-transfer step, the proton located at the retinal chromophore Schiff base is transferred to a nearby aspartate residue (Figure 14-6). Our studies on this first proton-transfer step in bacteriorhodopsin (bR) after photoisomerization [90,91,92]... 

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