title: Fluorescence kinetics of Trp-Trp dipeptide and its derivatives in water via ultrafast fluorescence spectroscopy.
abstract: Ultrafast fluorescence dynamics of Tryptophan-Tryptophan (Trp-Trp/Trp2) dipeptide and its derivatives in water have been investigated using a picosecond resolved time correlated single photon counting (TCSPC) apparatus together with a femtosecond resolved upconversion spectrophotofluorometer. The fluorescence decay profiles at multiple wavelengths were fitted by a global analysis technique. Nanosecond fluorescence kinetics of Trp2, N-tert-butyl carbonyl oxygen-N'-aldehyde group-l-tryptophan-l-tryptophan (NBTrp2), l-tryptophan-l-tryptophan methyl ester (Trp2Me), and N-acetyl-l-tryptophan-l-tryptophan methyl ester (NATrp2Me) exhibit multi-exponential decays with the average lifetimes of 1.99, 3.04, 0.72 and 1.22ns, respectively. Due to the intramolecular interaction between two Trp residues, the "water relaxation" lifetime was observed around 4ps, and it is noticed that Trp2 and its derivatives also exhibit a new decay with a lifetime of ∼100ps, while single-Trp fluorescence decay in dipeptides/proteins shows 20-30ps. The intramolecular interaction lifetime constants of Trp2, NBTrp2, Trp2Me and NATrp2Me were then calculated to be 3.64, 0.93, 11.52 and 2.40ns, respectively. Candidate mechanisms (including heterogeneity, solvent relaxation, quasi static self-quenching or ET/PT quenching) have been discussed.
authors.affiliation: State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, China.
authors.forename: Menghui
authors.initials: M
authors.lastname: Jia
authors.affiliation: State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, China.
authors.forename: Hua
authors.initials: H
authors.lastname: Yi
authors.affiliation: State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, China.
authors.forename: Mengfang
authors.initials: M
authors.lastname: Chang
authors.affiliation: State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, China.
authors.forename: Xiaodan
authors.initials: X
authors.lastname: Cao
authors.affiliation: State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, China.
authors.forename: Lei
authors.initials: L
authors.lastname: Li
authors.affiliation: State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, China.
authors.forename: Zhongneng
authors.initials: Z
authors.lastname: Zhou
authors.affiliation: State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, China.
authors.forename: Haifeng
authors.initials: H
authors.lastname: Pan
authors.affiliation: Tongji Hospital Affiliated to Tongji University, 389 Xincun Road, Shanghai 200065, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Chen
authors.affiliation: State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, China. Electronic address: sjzhang@phy.ecnu.edu.cn.
authors.forename: Sanjun
authors.initials: S
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, China.
authors.forename: Jianhua
authors.initials: J
authors.lastname: Xu
mesh_terms: D004151:Dipeptides / Q000737:chemistry*; D004579:Electron Transport; D007700:Kinetics; D013050:Spectrometry, Fluorescence; D014867:Water / Q000737:chemistry*
chemical_list: D004151:Dipeptides; C000606701:tryptophyltryptophan; D014867:Water
keywords: Decay associated spectra (DAS); Electron/proton transfer (ET/PT); Quasi static self-quenching (QSSQ); Time resolved fluorescence; Tryptophan dipeptides