title: Realization of a four-step molecular switch in scanning tunneling microscope manipulation of single chlorophyll-a molecules.
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 CH(3) 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.
authors.affiliation: Quantitative Biology Institute, Nanoscale and Quantum Phenomena Institute, and Department of Physics and Astronomy, Ohio University, Athens, OH 45701, USA.
authors.forename: Violeta
authors.initials: V
authors.lastname: Iancu
authors.forename: Saw-Wai
authors.initials: SW
authors.lastname: Hla
mesh_terms: D002734:Chlorophyll / Q000737:chemistry*; D004735:Energy Transfer; D006046:Gold / Q000737:chemistry; D016252:Microscopy, Scanning Tunneling; D008968:Molecular Conformation
chemical_list: D002734:Chlorophyll; D006046:Gold