Comparison of simultaneous biexponential and compartmental analyses of fluorescence decay surfaces of intermolecular two-state excited-state processes

Meuwis, Katrien; Depuydt, Gwendoline; Boens, Noël; Schryver, F. C. De

doi:10.1016/0009-2614(95)01169-9

Cited by 9 publications

(8 citation statements)

References 15 publications

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“…Different methods and strategies of analysis have been discussed to interpret the data obtained from time-resolved experiments. ,,− In a Birks'-type kinetic scheme, the simultaneous analysis of the decays, collected in the monomer and excimer emission regions, should be the most appropriate method of decay analysis because the two decay times are identical over all of the spectra and the only varying parameters are the preexponential factors. When additional components are present, this strategy of analysis may no longer be the most appropriate.…”

Section: Resultsmentioning

confidence: 99%

Time-Resolved and Steady-State Fluorescence Studies of Hydrophobically Modified Water-Soluble Polymers

et al. 2003

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A comprehensive study of the photophysical behavior of poly(acrylic acids) randomly labeled with pyrene using steady-state and time-resolved fluorescence spectroscopy is presented. The influence of external factors, such as different solvents and pH in the aqueous solution, on the polymer photophysics has been investigated. These factors induce major changes in the polymer conformation, which are reflected in the fluorescence experiments. The random introduction of the hydrophobic pyrene groups along the macromolecule favors the coexistence of static (preformed dimers) and dynamic (excimers) monomer quenching phenomena together with a fraction of isolated monomers (not able to form excimer), as revealed by time-resolved and steady-state fluorescence data. In dioxane and methanol solvents, the global analysis of the fluorescence time profiles shows a rise time of ∼21−32 ns followed by a decay of ∼90−138 ns with an additional longer decay component with a low preexponential factor. This is consistent with the fact that in organic solvents such as methanol and dioxane, which are considered to be good solvents, the fraction of preassociated and isolated chromophores is highly reduced and excimer formation is essentially due to a dynamic mechanism. A kinetic scheme involving two types of monomers (MA and MB) and one excimer (E) is proposed. From the fluorescence decays it was possible to extract quantitatively the percentage of ground-state preformed dimers along with the percentage of isolated chromophores at room temperature. In addition, it is shown that the fraction of associated ground-state chromophores that can be excited is always larger than that of the isolated chromophores. The rate constants for excimer formation (k a), dissociation (k d), and deactivation (k E) were determined considering the absence and presence of preformed dimers. Additional photophysical and spectroscopic data consisting of wavelength shifts, peak-to-valley ratios and differences (obtained both from absorption and from excitation spectra collected at the monomer and excimer emission region), and the vibronic I 1/I 3 ratio in the pyrene monomer emission were found to be pH-dependent for the polymers in aqueous solution. Hence, by combining the results from steady-state fluorescence measurements with time-resolved fluorescence data, information is provided on how the chain conformation of the labeled PAA polymers changes depending on the solvent (water at different pH values or organic solvents). In water, the conformation changes from compact at low pH to an open polymer coil at high pH, whereas the polymers are in an extended state when in dioxane and methanol.

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Section: Resultsmentioning

confidence: 99%

Time-Resolved and Steady-State Fluorescence Studies of Hydrophobically Modified Water-Soluble Polymers

et al. 2003

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“…The main advantage of global compartmental analysis lies in the possibility of recovering directly, with high accuracy and precision, the underlying parameters of the kinetic model (i.e., rate constants and spectral parameters associated with excitation and emission). 16 The determination of the parameters of interest is done by a single-step analysis of the complete decay data surface.…”

Section: Introductionmentioning

confidence: 99%

Absorption and Emission Study of 2‘,7‘-Difluorofluorescein and Its Excited-State Buffer-Mediated Proton Exchange Reactions

et al. 2005

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2′,7′-Difluorofluorescein (Oregon Green 488) is a new fluorescein-based dye, which has found many applications, above all in biochemistry and neurosciences, and its use has become very popular in the last years. In recent years, we have been investigating the excited-state proton exchange reactions of fluorescein and the effect of suitable proton acceptors and donors which promote these reactions. The excited-state proton transfer reactions may appreciably influence the fluorescence results when using these dyes. We present steady-state emission evidence that acetate buffer species promote an excited-state proton transfer between neutral, monoanionic, and dianionic forms of 2′,7′-difluorofluorescein. The time course of the excited species in this reaction was characterized through time-resolved fluorescence measurements, and the kinetics of the reaction was solved by using the global compartmental analysis. A previous identifiability study on the compartmental system set the conditions to design the fluorescence decay surface. This is the first experimental system, studied within this kinetic model, solved under identifiability conditions through global compartmental analysis. The recovered rate constant values for deactivation were 2.94 × 10 8 s -1 for the monoanion and 2.47 × 10 8 s -1 for the dianion, whereas the rate constant values of the buffer-mediated excited-state reaction were 9.70 × 10 8 and 1.79 × 10 8 M -1 s -1 for the deprotonation and protonation, respectively. With these values, a pK a * ) 4.02 was obtained. In this work, we additionally provide an absorption study, including acid-base equilibria, determination of ground-state pK a values (1.02, 3.61, and 4.69), and recovery of molar absorption coefficients of every prototropic species, including absorption and NMR evidence for the existence of three tautomers in neutral species. Steady-state emission spectra of 2′,7′-difluorofluorescein in aqueous solution are also described, where the strong photoacid behavior of the cation is noteworthy.

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“…It has been shown 16 that global compartmental analysis is a very sensitive method for distinguishing between competing kinetic models. The steady-state (Hill plot) and time-resolved fluorescence (two decay times) data as a function of [Na + ] are compatible with the kinetic model depicted in Scheme 1.…”

Section: Discussionmentioning

confidence: 99%

Photophysics of SBFO: A Fluorescent Indicator for Na⁺

et al. 1998

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SBFO is a commercially available fluorescent indicator for the determination of Na+ concentrations. To investigate the reversible reaction of Na+ with this indicator in the ground and excited states, steady-state and time-resolved fluorescence measurements were performed. Global compartmental analysis was used to describe the fluorescence decay surfaces yielding the following values for the rate constants at room temperature in aqueous solution at pH 7.2: k 01 = 5 × 108 s-1, 2 × 107 M-1 s-1 < k 21 < 3 × 108 M-1 s-1, k 02 = 5 × 108 s-1, k 12 = 1 × 108 s-1. k 01 and k 02 denote the respective deactivation rate constants of the Na+ free and bound forms of the indicator in the excited state. k 21 represents the second-order rate constant of association of Na+ with SBFO in the excited state, whereas k 12 is the first-order rate constant of dissociation of the excited Na+−indicator complex. The effect of the reversible excited-state reaction between Na+ and the indicator on the fluorimetric determination of K d can be neglected.

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Comparison of simultaneous biexponential and compartmental analyses of fluorescence decay surfaces of intermolecular two-state excited-state processes

Cited by 9 publications

References 15 publications

Time-Resolved and Steady-State Fluorescence Studies of Hydrophobically Modified Water-Soluble Polymers

Time-Resolved and Steady-State Fluorescence Studies of Hydrophobically Modified Water-Soluble Polymers

Absorption and Emission Study of 2‘,7‘-Difluorofluorescein and Its Excited-State Buffer-Mediated Proton Exchange Reactions

Photophysics of SBFO: A Fluorescent Indicator for Na⁺

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Comparison of simultaneous biexponential and compartmental analyses of fluorescence decay surfaces of intermolecular two-state excited-state processes

Cited by 9 publications

References 15 publications

Time-Resolved and Steady-State Fluorescence Studies of Hydrophobically Modified Water-Soluble Polymers

Time-Resolved and Steady-State Fluorescence Studies of Hydrophobically Modified Water-Soluble Polymers

Absorption and Emission Study of 2‘,7‘-Difluorofluorescein and Its Excited-State Buffer-Mediated Proton Exchange Reactions

Photophysics of SBFO: A Fluorescent Indicator for Na+

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Photophysics of SBFO: A Fluorescent Indicator for Na⁺