Ultrafast Excited-State Dynamics of DNA Fluorescent Intercalators: New Insight into the Fluorescence Enhancement Mechanism

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• 作者：Alexandre Fü ; rstenberg ; Marc D. Julliard ; Todor G. Deligeorgiev ; Nikolai I. Gadjev ; Aleksey A. Vasilev ; and Eric Vauthey
• 刊名：Journal of the American Chemical Society
• 出版年：2006
• 出版时间：June 14, 2006
• 年：2006
• 卷：128
• 期：23
• 页码：7661 - 7669
• 全文大小：397K
• 年卷期：v.128,no.23(June 14, 2006)
• ISSN：1520-5126

文摘

The excited-state dynamics of the DNA bisintercalator YOYO-1 and of two derivatives has beeninvestigated using ultrafast fluorescence up-conversion and time-correlated single photon counting. Thefree dyes in water exist in two forms: nonaggregated dyes and intramolecular H-type aggregates, thelatter form being only very weakly fluorescent because of excitonic interaction. The excited-state dynamicsof the nonaggregated dyes is dominated by a nonradiative decay with a time constant of the order of 5 psassociated with large amplitude motion around the monomethine bridge of the cyanine chromophores.The strong fluorescence enhancement observed upon binding of the dyes to DNA is due to both the inhibitionof this nonradiative deactivation of the nonaggregated dyes and the dissociation of the aggregates andthus to the disruption of the excitonic interaction. However, the interaction between the two chromophoricmoieties in DNA is sufficient to enable ultrafast hopping of the excitation energy as revealed by the decayof the fluorescence anisotropy. Finally, these dyes act as solvation probes since a dynamic fluorescenceStokes shift was observed both in bulk water and in DNA. Very similar time scales were found in bulkwater and in DNA.