Direct triazine herbicide detection using a self-assembled photosynthetic reaction center from purple bacterium

2000 ◽  
Vol 5 (6) ◽  
pp. 413-417 ◽  
Author(s):  
Chikashi Nakamura ◽  
Miki Hasegawa ◽  
Kazumi Shimada ◽  
Makoto Shirai ◽  
Jun Miyake
Keyword(s):  
Reaction Center ◽  
Photosynthetic Reaction Center ◽  
Purple Bacterium ◽  
Triazine Herbicide ◽  
Self Assembled

Co-facial magnesium porphyrin dimer complexed with fullerene: photosynthetic reaction center model of 'special pair' self-assembled to electron acceptor

2008 ◽  
Vol 12 (07) ◽  
pp. 857-865 ◽  
Author(s):  
Atula S. D. Sandanayaka ◽  
Navaneetha K. Subbaiyan ◽  
Raghu Chitta ◽  
Yasuyuki Araki ◽  
Osamu Ito ◽  
...  
Keyword(s):  
Reaction Center ◽  
Electron Acceptor ◽  
Photosynthetic Reaction Center ◽  
Ammonium Cation ◽  
Model Systems ◽  
Spectral Studies ◽  
Special Pair ◽  
Self Assembled ◽  
Alkyl Ammonium ◽  
Porphyrin Dimer

Using a self-assembled supramolecular approach, a closer model for the photosynthetic reaction center 'special pair' assembled with an electron acceptor conjugate, is reported. As the 'special pair' donor, magnesium meso-(benzo-15-crown-5)porphyrin was self-assembled with K + to form a highly stable Mg porphyrin dimer with a co-facial geometry arrangement, which is a better electron donor since it is nearly 130 mV easier to oxidize compared to the earlier reported Zn porphyrin dimer analog. Further, pyridine and alkyl ammonium cation-functionalized fullerene was attached via axial coordination and crown ether-alkyl ammonium cation complexation to form the four-fold, donor-acceptor complex. The self-assembled supramolecular complex, constructed using this approach, possesses defined geometry and orientation. Efficient charge separation from the singlet excited state of the Mg porphyrin dimer to the fullerene entity and a relatively slow charge recombination, were revealed by time-resolved emission and nanosecond transient absorption spectral studies, supporting the impending exploitation of these novel biomimetic model systems for light energy harvesting applications.

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