title: Ultrafast photoinduced electron transfer between tetramethylrhodamine and guanosine in aqueous solution.
abstract: Photoinduced electron transfer based fluorescence correlation spectroscopy (PET-FCS) is a powerful tool to study biomolecular processes. However, some questions remain as to how to correctly interpret the PET-FCS data. In this work, we studied the PET process between tetramethylrhodamine and guanosine by means of femtosecond transient absorption spectroscopy. We derived that the charge separation rate is 4.1 × 10(9) s(-1) and the charge recombination rate is 5.2 × 10(10) s(-1) for the current system, supporting the three-state model and the interpretation on PET-FCS experiments given by Qu et al. (J. Phys Chem. B, 2010, 114, 8235). At the limit that both the charge separation and recombination rates are much faster than the process that PET-FCS reveals, the three-state model can be simplified to an equivalent two-state model with a dark state whose brightness is nonzero. We propose ways to obtain the brightness of the dark state with additional experiments, which is necessary for a PET-FCS study.
authors.affiliation: Beijing National Laboratory for Molecular Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Department of Chemical Biology, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, People's Republic of China.
authors.forename: Xun
authors.initials: X
authors.lastname: Li
authors.forename: Ruixue
authors.initials: R
authors.lastname: Zhu
authors.forename: Anchi
authors.initials: A
authors.lastname: Yu
authors.forename: Xin Sheng
authors.initials: XS
authors.lastname: Zhao
mesh_terms: D004579:Electron Transport; D006151:Guanosine / Q000737:chemistry*; D012235:Rhodamines / Q000737:chemistry*; D012996:Solutions / Q000737:chemistry; D013050:Spectrometry, Fluorescence; D014867:Water / Q000737:chemistry
chemical_list: D012235:Rhodamines; D012996:Solutions; D014867:Water; D006151:Guanosine; C005358:tetramethylrhodamine