Light Harvesting Antennae

With tlie development of femtosecond laser teclmology it has become possible to observe in resonance energy transfer some apparent manifestations of tire coupling between nuclear and electronic motions. For example in photosyntlietic preparations such as light-harvesting antennae and reaction centres [32, 46, 47 and 49] such observations are believed to result eitlier from oscillations between tire coupled excitonic levels of dimers (generally multimers), or tire nuclear motions of tire cliromophores. This is a subject tliat is still very much open to debate, and for extensive discussion we refer tire reader for example to [46, 47, 50, 51 and 55]. A simplified view of tire subject can nonetlieless be obtained from tire following semiclassical picture. 

Identification of Carotenoids in Photosynthetic Proteins Xanthophylls of the Light Harvesting Antenna... 

Localization and Functions of Xanthophylls in Light Harvesting Antenna of Plants.117... 

It is therefore important to bear in mind the dependency of the carotenoid spectrum upon properties of the environment for in vivo analysis, which is based on the application of optical spectroscopies. This approach is often the only way to study the composition, structure, and biological functions of carotenoids. Spectral sensitivity of xanthophylls to the medium could be a property to use for gaining vital information on their binding sites and dynamics. The next sections will provide a brief introduction to the structure of the environment with which photosynthetic xanthophylls interact—light harvesting antenna complexes (LHC). 

LOCALIZATION AND FUNCTIONS OF XANTHOPHYLLS IN LIGHT HARVESTING ANTENNA OF PLANTS... 

Ruban, A.V., Pascal, A.A., Robert, B., and Horton, P. 2001. Configuration and dynamics of carotenoids in light-harvesting antennae of the thylakoid membrane. J. Biol. Chem. 276 24862-24870. 

Polivka, T., M. Pellnor, E. Melo, T. Pascher, V. Sundstrom, A. Osuka, and K. R. Naqvi. 2007. Polarity-tuned energy transfer efficiency in artificial light-harvesting antennae containing carbonyl carotenoids peridi-nin and fucoxanthin. J. Phys. Chem. C 110 467 -76. 

Trinkunas, G., J. L. Herek, T. Polfvka, V. Sundstrom, and T. Pullerits. 2001. Exciton delocalization probed by excitation annihilation in the light-harvesting antenna LH2. Phys. Rev. Lett. 86 4167 4170. 

Supermolecular interlocked macromolecules have been paid much attention as candidates of smart materials. Polyrotaxane (PRX) is a typical example. PEG/ cyclodextrin (CD)-based polyrotaxane was firstly reported by Harada and coworkers by attachment of stoppers to pseudopolyrotaxane (pPRX) consisting of a PEG and CDs [263]. Subsequently, many CD-based PRXs have been designed and prepared as smart materials such as biomaterials, light-harvesting antennae, insulating polymers, stimuli-responsive molecular shuttles etc. [264—268]. 

Amphiphilic compounds and other chemicals used are shown in Figs. 5 [3,4] and 6 [36] together with their abbreviations. The synthetic procedures for A-S-D triad, A-S dyad, and H light harvesting antenna molecules in Fig. 5 were described previously [3,37,38]. A cationic cyanine dye with two long alkyl chains (CD) in Fig. 5 was purchased from Japanese Research Institute for Photosensitizing Dyes,... 

His research interests deal with the chemistry of cyclopropane derivatives, 1,3-dipolar cycloadditions, synthesis of natural compounds and biologically active analogues. Recently, the research activity is also dedicated to synthetic studies for the production of new materials light-harvesting antenna systems and functionalized organogelators. 

Figure 13.14 Light harvesting antenna reported by Fox and coworkers...

Nonradiative energy transfer has a major role in the process of photosynthesis. Light is absorbed by large numbers of chlorophyll molecules in light-harvesting antennae and energy is transferred in a stepwise manner to photosynthetic reaction centres, at which photochemical reactions occur. This fundamental energy-transfer process will be considered in more detail in Chapter 12. 

A current example of the value of shape persistent dendrimers in fundamental research is their use in the study of electron transfer processes between different redox centers. If one redox center is situated in the core and another redox center is located in the shell at a distinct distance from the other center, the distances which are necessary for an electron transfer to take place can be studied. This currently presents an objective of our research. Furthermore, dendrimers coated with two types of functionalities at the periphery are currently under intense investigation. The attachment of two different types of dyes at the periphery is of interest in the study of the energy transfer between these dyes (light harvesting antenna). 

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