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Noel Boens - One of the best experts on this subject based on the ideXlab platform.

  • kinetics and identifiability of intramolecular two state excited state processes with added quencher global compartmental analysis of the Fluorescence Decay surface
    1993
    Co-Authors: Noel Boens, Marcel Ameloot, R Hermans, Fc Deschryver, Ronn Andriessen
    Abstract:

    The Fluorescence Decay analysis of intramolecular two-state excited-state processes with added quencher is discussed in terms of compartments. The kinetics specifying the two excited-state species concentrations are derived. The Fluorescence Decay surface is expressed in terms of the system parameters, namely the rate constants and the spectroscopic parameters b 1 and c 1 . b 1 and c 1 are respectively the relative absorbance and the normalized spectral emission weighting factor of species 1. The report investigates the prerequisites for obtaining the unique set of system parameters

  • species associated spectra and upper and lower bounds on the rate constants of reversible intramolecular two state excited state processes with added quencher global compartmental analysis of the Fluorescence Decay surface
    1993
    Co-Authors: Luc Van Dommelen, Noel Boens, Frans C De Schryver, Marcel Ameloot, Andrzej Kowalczyk
    Abstract:

    This paper explains how, in the absence of any a priori information, upper and lower bounds can be specified for the four rate constants describing the kinetics of a reversible intramolecular two-state excited-state process. It is further shown that the steady-state spectrum can be decomposed into unique species-associated spectra. It is demonstrated theoretically that if the Fluorescence Decay surface includes at least one set of Decay traces measured at a minimum of three different quencher concentrations, it is possible to specify limits on the rate constants and to construct the species-associated spectra. The two quenching rate constants must be different. This new analysis method allows one to distinguish reversible from irreversible intramolecular two-state excited-state processes

  • compartmental analysis of the Fluorescence Decay surface of intramolecular two state excited state processes with added quencher
    1992
    Co-Authors: Noel Boens, Ronn Andriessen, Frans C De Schryver, Marcel Ameloot, Luc Van Dommelen, Bart Hermans
    Abstract:

    The Fluorescence Decay analysis of intramolecular two-state excited-state processes with added quencher is discussed in terms of compartments. The kinetic equations specifying the Fluorescence Decay and the time-course of the two excited-state species concentrations are expressed in terms of the rate constants and the spectroscopic parameters b1 and c1. b1 and c1 are respectively the relative absorbance and the normalized spectral emission weighting factor of species 1. The report investigates what has to be known beforehand to determine all relevant parameters. The results of this identifiability study indicate that the following conditions have to be satisfied in order to make an intramolecular two-state excited-state system with added quencher identifiable. First, at least three different quencher concentrations must be used. Second, the two rate constants of quenching must be different. Third, at least one parameter must be known. This parameter can be (1) one rate constant which is not a rate constant of quenching, (2) one b1 value or, (3) one c1 value. In each of these cases an alternative set of system parameters is mathematically possible. A unique solution is guaranteed when the Fluorescence Decays of a quenched model compound are included in the compartmental analysis.© (1992) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

  • photophysics of tryptophan global analysis of the Fluorescence Decay surface as a function of ph temperature quencher concentration excitation and emission wavelengths timing calibration and deuterium isotope effect
    1992
    Co-Authors: Noel Boens, Frans C De Schryver, Luc Van Dommelen, Luc Janssens, Jacques Gallay
    Abstract:

    The Fluorescence Decay surface of tryptophan measured over a very wide pH range (1.35 to 12.38) was analyzed in a single global analysis. It is clear that the Decay components remain the same over the whole pH range. This is also confirmed by the Decay-associated emission spectra. At low pH the Decays are biexponential and both Decay components contribute to the Fluorescence up to pH 11. From about pH 7.5 onwards a third component has to be taken into account which becomes the only component at pH > 11. The Decay times decrease at low pH due to quenching by H3O+. At pH > 11 the Decay times decline due to quenching by OH-. Decays collected at different temperatures at neutral pH indicate that the short Decay time is independent of temperature, both in H2O and D2O solution. Both Decay times increase by a factor of two when H2O is replaced by D2O as solvent. The Decay times and their normalized pre-exponential terms at neutral pH in H2O solution are constant as a function of excitation wavelength (from 250 to 295 nm). This indicates that the absorption spectra associated with the two ground-state species overlap completely and that the contribution of both species to the total absorption remains constant over the whole absorption spectrum.© (1992) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

  • compartmental analysis of Fluorescence Decay surfaces of excited state processes
    1992
    Co-Authors: Marcel Mameloot, Noel Boens, Ronn Andriessen, Viviane Van Den Bergh, Frans C De Schryver
    Abstract:

    Publisher Summary This chapter discusses the identifiability of two-state excited-state processes with known concentration dependence in the forward process. It is demonstrated that the Decay curves in a Fluorescence Decay surface do not need to be normalized to perform a global analysis in terms of the parameters of interest. The normalization of Decay curves is a tedious and sometimes even impossible task. The steady-state spectra can be used afterward to obtain the species-associated spectra. The chapter describes the excited-state processes with time-independent rate constants. The identifiability equations and the identifiability of a two-state excited-state process are discussed in the chapter.. The chapter discusses the way the species-associated spectra can be calculated using the information obtained from the analysis of the Decay surface and steady-state spectra. The chapter presents some indications to extend existing global analysis programs to compartmental analysis. The determination of the ground-state equilibrium constant is then discussed in the chapter.

Laura Marcu - One of the best experts on this subject based on the ideXlab platform.

  • a novel method for fast and robust estimation of Fluorescence Decay dynamics using constrained least squares deconvolution with laguerre expansion
    2012
    Co-Authors: Jing Liu, Yang Sun, Laura Marcu
    Abstract:

    We report a novel method for estimating Fluorescence impulse response function (fIRF) from noise-corrupted time-domain Fluorescence measurements of biological tissue. This method is based on the use of high-order Laguerre basis functions and a constrained least-squares approach that addresses the problem of overfitting due to increased model complexity. The new method was extensively evaluated on Fluorescence data from simulation, fluorescent standard dyes, ex vivo tissue samples of atherosclerotic plaques and in vivo oral carcinoma. Current results demonstrate that this method allows for rapid and accurate deconvolution of multiple channel Fluorescence Decays without adaptively adjusting the Laguerre scale parameter. The appropriate choice of the scale parameter is essential for accurate estimation of the fIRF. The method described here is anticipated to play an important role in the development of computational techniques for real-time analysis of time-resolved Fluorescence data from biological tissues and to support the advancement of Fluorescence lifetime instrumentation for biomedical diagnostics by providing a means for on-line robust analysis of Fluorescence Decay.

  • fast model free deconvolution of Fluorescence Decay for analysis of biological systems
    2004
    Co-Authors: Qiyin Fang, Thanassis Papaioannou, Laura Marcu
    Abstract:

    For complex biological systems, conventional analysis of Fluorescence intensity Decay in terms of discrete exponential components cannot readily provide a true representation of the underlying Fluorescence dynamics. We investigate an alternative nonparametric method for the analysis of time-resolved Fluorescence data from biochemical and biological systems based on the expansion of Fluorescence Decay in a discrete Laguerre basis. We report that a unique Laguerre expansion can be found for Fluorescence intensity Decays of arbitrary form with convergence to a correct solution significantly faster than conventional multiexponential approximation methods. The Laguerre expansion coefficients are shown to be highly correlated with intrinsic Fluorescence lifetimes and allow direct characterization of the Fluorescence dynamics. A novel method for prediction of concentrations in mixtures of biochemical components using these coefficients is developed and successfully tested (prediction error <2%) using data from different mixtures of Fluorescence lifetime standards. These findings suggest that the use of Laguerre expansion coefficients is a fast approach for the characterization and discrimination of complex biological systems such as tissues and cells, and that the method has potential for applications of Fluorescence lifetime techniques to tissue diagnostics and imaging microscopy of living cells.

Frans C De Schryver - One of the best experts on this subject based on the ideXlab platform.

  • species associated spectra and upper and lower bounds on the rate constants of reversible intramolecular two state excited state processes with added quencher global compartmental analysis of the Fluorescence Decay surface
    1993
    Co-Authors: Luc Van Dommelen, Noel Boens, Frans C De Schryver, Marcel Ameloot, Andrzej Kowalczyk
    Abstract:

    This paper explains how, in the absence of any a priori information, upper and lower bounds can be specified for the four rate constants describing the kinetics of a reversible intramolecular two-state excited-state process. It is further shown that the steady-state spectrum can be decomposed into unique species-associated spectra. It is demonstrated theoretically that if the Fluorescence Decay surface includes at least one set of Decay traces measured at a minimum of three different quencher concentrations, it is possible to specify limits on the rate constants and to construct the species-associated spectra. The two quenching rate constants must be different. This new analysis method allows one to distinguish reversible from irreversible intramolecular two-state excited-state processes

  • compartmental analysis of the Fluorescence Decay surface of intramolecular two state excited state processes with added quencher
    1992
    Co-Authors: Noel Boens, Ronn Andriessen, Frans C De Schryver, Marcel Ameloot, Luc Van Dommelen, Bart Hermans
    Abstract:

    The Fluorescence Decay analysis of intramolecular two-state excited-state processes with added quencher is discussed in terms of compartments. The kinetic equations specifying the Fluorescence Decay and the time-course of the two excited-state species concentrations are expressed in terms of the rate constants and the spectroscopic parameters b1 and c1. b1 and c1 are respectively the relative absorbance and the normalized spectral emission weighting factor of species 1. The report investigates what has to be known beforehand to determine all relevant parameters. The results of this identifiability study indicate that the following conditions have to be satisfied in order to make an intramolecular two-state excited-state system with added quencher identifiable. First, at least three different quencher concentrations must be used. Second, the two rate constants of quenching must be different. Third, at least one parameter must be known. This parameter can be (1) one rate constant which is not a rate constant of quenching, (2) one b1 value or, (3) one c1 value. In each of these cases an alternative set of system parameters is mathematically possible. A unique solution is guaranteed when the Fluorescence Decays of a quenched model compound are included in the compartmental analysis.© (1992) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

  • photophysics of tryptophan global analysis of the Fluorescence Decay surface as a function of ph temperature quencher concentration excitation and emission wavelengths timing calibration and deuterium isotope effect
    1992
    Co-Authors: Noel Boens, Frans C De Schryver, Luc Van Dommelen, Luc Janssens, Jacques Gallay
    Abstract:

    The Fluorescence Decay surface of tryptophan measured over a very wide pH range (1.35 to 12.38) was analyzed in a single global analysis. It is clear that the Decay components remain the same over the whole pH range. This is also confirmed by the Decay-associated emission spectra. At low pH the Decays are biexponential and both Decay components contribute to the Fluorescence up to pH 11. From about pH 7.5 onwards a third component has to be taken into account which becomes the only component at pH > 11. The Decay times decrease at low pH due to quenching by H3O+. At pH > 11 the Decay times decline due to quenching by OH-. Decays collected at different temperatures at neutral pH indicate that the short Decay time is independent of temperature, both in H2O and D2O solution. Both Decay times increase by a factor of two when H2O is replaced by D2O as solvent. The Decay times and their normalized pre-exponential terms at neutral pH in H2O solution are constant as a function of excitation wavelength (from 250 to 295 nm). This indicates that the absorption spectra associated with the two ground-state species overlap completely and that the contribution of both species to the total absorption remains constant over the whole absorption spectrum.© (1992) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

  • compartmental analysis of Fluorescence Decay surfaces of excited state processes
    1992
    Co-Authors: Marcel Mameloot, Noel Boens, Ronn Andriessen, Viviane Van Den Bergh, Frans C De Schryver
    Abstract:

    Publisher Summary This chapter discusses the identifiability of two-state excited-state processes with known concentration dependence in the forward process. It is demonstrated that the Decay curves in a Fluorescence Decay surface do not need to be normalized to perform a global analysis in terms of the parameters of interest. The normalization of Decay curves is a tedious and sometimes even impossible task. The steady-state spectra can be used afterward to obtain the species-associated spectra. The chapter describes the excited-state processes with time-independent rate constants. The identifiability equations and the identifiability of a two-state excited-state process are discussed in the chapter.. The chapter discusses the way the species-associated spectra can be calculated using the information obtained from the analysis of the Decay surface and steady-state spectra. The chapter presents some indications to extend existing global analysis programs to compartmental analysis. The determination of the ground-state equilibrium constant is then discussed in the chapter.

Ronn Andriessen - One of the best experts on this subject based on the ideXlab platform.

  • kinetics and identifiability of intramolecular two state excited state processes with added quencher global compartmental analysis of the Fluorescence Decay surface
    1993
    Co-Authors: Noel Boens, Marcel Ameloot, R Hermans, Fc Deschryver, Ronn Andriessen
    Abstract:

    The Fluorescence Decay analysis of intramolecular two-state excited-state processes with added quencher is discussed in terms of compartments. The kinetics specifying the two excited-state species concentrations are derived. The Fluorescence Decay surface is expressed in terms of the system parameters, namely the rate constants and the spectroscopic parameters b 1 and c 1 . b 1 and c 1 are respectively the relative absorbance and the normalized spectral emission weighting factor of species 1. The report investigates the prerequisites for obtaining the unique set of system parameters

  • compartmental analysis of the Fluorescence Decay surface of intramolecular two state excited state processes with added quencher
    1992
    Co-Authors: Noel Boens, Ronn Andriessen, Frans C De Schryver, Marcel Ameloot, Luc Van Dommelen, Bart Hermans
    Abstract:

    The Fluorescence Decay analysis of intramolecular two-state excited-state processes with added quencher is discussed in terms of compartments. The kinetic equations specifying the Fluorescence Decay and the time-course of the two excited-state species concentrations are expressed in terms of the rate constants and the spectroscopic parameters b1 and c1. b1 and c1 are respectively the relative absorbance and the normalized spectral emission weighting factor of species 1. The report investigates what has to be known beforehand to determine all relevant parameters. The results of this identifiability study indicate that the following conditions have to be satisfied in order to make an intramolecular two-state excited-state system with added quencher identifiable. First, at least three different quencher concentrations must be used. Second, the two rate constants of quenching must be different. Third, at least one parameter must be known. This parameter can be (1) one rate constant which is not a rate constant of quenching, (2) one b1 value or, (3) one c1 value. In each of these cases an alternative set of system parameters is mathematically possible. A unique solution is guaranteed when the Fluorescence Decays of a quenched model compound are included in the compartmental analysis.© (1992) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

  • compartmental analysis of Fluorescence Decay surfaces of excited state processes
    1992
    Co-Authors: Marcel Mameloot, Noel Boens, Ronn Andriessen, Viviane Van Den Bergh, Frans C De Schryver
    Abstract:

    Publisher Summary This chapter discusses the identifiability of two-state excited-state processes with known concentration dependence in the forward process. It is demonstrated that the Decay curves in a Fluorescence Decay surface do not need to be normalized to perform a global analysis in terms of the parameters of interest. The normalization of Decay curves is a tedious and sometimes even impossible task. The steady-state spectra can be used afterward to obtain the species-associated spectra. The chapter describes the excited-state processes with time-independent rate constants. The identifiability equations and the identifiability of a two-state excited-state process are discussed in the chapter.. The chapter discusses the way the species-associated spectra can be calculated using the information obtained from the analysis of the Decay surface and steady-state spectra. The chapter presents some indications to extend existing global analysis programs to compartmental analysis. The determination of the ground-state equilibrium constant is then discussed in the chapter.

Nobuhiro Ohta - One of the best experts on this subject based on the ideXlab platform.