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Science 7 July 2006:
Vol. 313. no. 5783, pp. 84 - 86
DOI: 10.1126/science.1126524
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Reports

Photoproduction of Proton Gradients with {pi}-Stacked Fluorophore Scaffolds in Lipid Bilayers

Sheshanath Bhosale,1 Adam L. Sisson,1 Pinaki Talukdar,1 Alexandre Fürstenberg,2 Natalie Banerji,2 Eric Vauthey,2 Guillaume Bollot,1 Jiri Mareda,1 Cornelia Röger,3 Frank Würthner,3 Naomi Sakai,1 Stefan Matile1*

Rigid p-octiphenyl rods were used to create helical tetrameric {pi}-stacks of blue, red-fluorescent naphthalene diimides that can span lipid bilayer membranes. In lipid vesicles containing quinone as electron acceptors and surrounded by ethylenediaminetetraacetic acid as hole acceptors, transmembrane proton gradients arose through quinone reduction upon excitation with visible light. Quantitative ultrafast and relatively long-lived charge separation was confirmed as the origin of photosynthetic activity by femtosecond fluorescence and transient absorption spectroscopy. Supramolecular self-organization was essential in that photoactivity was lost upon rod shortening (from p-octiphenyl to biphenyl) and chromophore expansion (from naphthalene diimide to perylene diimide). Ligand intercalation transformed the photoactive scaffolds into ion channels.

1 Department of Organic Chemistry, University of Geneva, Geneva, Switzerland.
2 Department of Physical Chemistry, University of Geneva, Geneva, Switzerland.
3 Institut für Organische Chemie, Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany.

* To whom correspondence should be addressed. E-mail: stefan.matile{at}chiorg.unige.ch

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Science. ISSN 0036-8075 (print), 1095-9203 (online)