title: Ultrafast fluorescence quenching dynamics of Atto655 in the presence of N-acetyltyrosine and N-acetyltryptophan in aqueous solution: proton-coupled electron transfer versus electron transfer.
abstract: We studied the ultrafast fluorescence quenching dynamics of Atto655 in the presence of N-acetyltyrosine (AcTyr) and N-acetyltryptophan (AcTrp) in aqueous solution with femtosecond transient absorption spectroscopy. We found that the charge-transfer rate between Atto655 and AcTyr is about 240 times smaller than that between Atto655 and AcTrp. The pH value and D2O dependences of the excited-state decay kinetics of Atto655 in the presence of AcTyr and AcTrp reveal that the quenching of Atto655 fluorescence by AcTyr in aqueous solution is via a proton-coupled electron-transfer (PCET) process and that the quenching of Atto655 fluorescence by AcTrp in aqueous solution is via an electron-transfer process. With the version of the semiclassical Marcus ET theory, we derived that the electronic coupling constant for the PCET reaction between Atto655 and AcTyr in aqueous solution is 8.3 cm(-1), indicating that the PCET reaction between Atto655 and AcTyr in aqueous solution is nonadiabatic.
authors.affiliation: Department of Chemistry, Renmin University of China, Beijing 100872, People's Republic of China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Zhang
authors.forename: Shuwei
authors.initials: S
authors.lastname: Yuan
authors.forename: Rong
authors.initials: R
authors.lastname: Lu
authors.forename: Anchi
authors.initials: A
authors.lastname: Yu
mesh_terms: D004579:Electron Transport; D004583:Electrons; D005453:Fluorescence; D005456:Fluorescent Dyes / Q000737:chemistry*; D006576:Heterocyclic Compounds, 4 or More Rings / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D056004:Molecular Dynamics Simulation; D015394:Molecular Structure; D011370:Proflavine / Q000031:analogs & derivatives; D011522:Protons; D012996:Solutions; D014364:Tryptophan / Q000031:analogs & derivatives* / Q000737:chemistry; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000737:chemistry; D014867:Water / Q000737:chemistry
chemical_list: C582139:ATTO 465; C585841:Atto655; D005456:Fluorescent Dyes; D006576:Heterocyclic Compounds, 4 or More Rings; D011522:Protons; D012996:Solutions; D014867:Water; D014443:Tyrosine; C006392:N-acetyltryptophan; D014364:Tryptophan; D011370:Proflavine; C025787:N-acetyltyrosine