Realization of a four-step molecular switch in scanning tunneling microscope manipulation of single chlorophyll-a molecules
- Quantitative Biology Institute, Nanoscale and Quantum Phenomena Institute, and Department of Physics and Astronomy, Ohio University, Athens, OH 45701
-
Edited by Robert H. Austin, Princeton University, Princeton, NJ, and approved July 20, 2006 (received for review May 5, 2006)
Abstract
Single chlorophyll-a molecules, a vital resource for the sustenance of life on Earth, have been investigated by using scanning tunneling microscope manipulation and spectroscopy on a gold substrate at 4.6 K. Chlorophyll-a binds on Au(111) via its porphyrin unit while the phytyl-chain is elevated from the surface by the support of four CH3 groups. By injecting tunneling electrons from the scanning tunneling microscope tip, we are able to bend the phytyl-chain, which enables the switching of four molecular conformations in a controlled manner. Statistical analyses and structural calculations reveal that all reversible switching mechanisms are initiated by a single tunneling-electron energy-transfer process, which induces bond rotation within the phytyl-chain.
Footnotes
- *To whom correspondence should be addressed. E-mail: hla{at}ohio.edu
-
Author contributions: S.-W.H. designed research; V.I. performed research; V.I. and S.-W.H. analyzed data; and S.-W.H. wrote the paper.
-
Conflict of interest statement: No conflicts declared.
-
This paper was submitted directly (Track II) to the PNAS office.
- Abbreviation:
- STM,
- scanning tunneling microscope.
-
Freely available online through the PNAS open access option.
- © 2006 by The National Academy of Sciences of the USA
