Fluorescence decay kinetics

Fig. 2 The changes in fluorescence decay kinetics on binding the analyte, (a) The analyte is the dynamic quencher. The decay becomes shorter gradually as a function of its concentration, (b) The analyte binding changes the lifetime. Superposition of decay kinetics of bound and unbound forms is observed...

Broos J, Maddalena F, Hesp BH (2004) In vivo synthesized proteins with monoexponential fluorescence decay kinetics. J Am Chem Soc 126 22-23... 

The fluorescence decay kinetics of exemplary chosen QDs and small organic dyes are compared in Fig. 2. The size of the fluorescence parameter luminescence lifetime is determined by the electronic nature of the transitions involved. As a rule... 

J. R. Lakowicz, G. Laczko, H. Cherek, E. Gratton, and M. Limkeman, Analysis of fluorescence decay kinetics from variable-frequency phase shift and modulation data, Biophys. J. 46, 463—+77 (1984). 

K. J. Willis and A. G. Szabo, The fluorescence decay kinetics of tyrosinate and tyrosine hydrogen bonded complexes, J. Phys. Chem. 95, 1585-1589 (1991). 

J. B. A. Ross, W. R. Laws, J. C. Sutherland, A. Buku, P. G. Katsoyannis, I. L. Schwartz, and H. R. Wyssbrod, Linked-function analysis of fluorescence decay kinetics Resolution of side-chain rotamer populations of a single aromatic amino acid in small polypeptides, Photochem. Photobiol. 44, 365-370 (1986). 

In this section, the information on structure and dynamics of proteins which may be obtained from direct observations of fluorescence decay will be considered. This type of information is afforded by methods which permit fluorescence decay kinetics to be followed with picosecond and nanosecond resolution. 

Proteins having one chromophore per molecule are the simplest and most convenient in studies of fluorescence decay kinetics as well as in other spectroscopic studies of proteins. These were historically the first proteins for which the tryptophan fluorescence decay was analyzed. It was natural to expect that, for these proteins at least, the decay curves would be singleexponential. However, a more complex time dependence of the emission was observed. To describe the experimental data for almost all of the proteins studied, it was necessary to use a set of two or more exponents.(2) The decay is single-exponential only in the case of apoazurin.(41) Several authors(41,42) explained the biexponentiality of the decay by the existence of two protein conformers in equilibrium. Such an explanation is difficult to accept without additional analysis, since there are many other mechanisms leading to nonexponential decay and in view of the fact that deconvolution into exponential components is no more than a formal procedure for treatment of nonexponential curves. 

One can expect that the analysis of continuous distributions of electronic excited-state lifetimes will not only provide a higher level of description of fluorescence decay kinetics in proteins but also will allow the physical mechanisms determining the interactions of fluorophores with their environment in protein molecules to be elucidated. Two physical causes for such distributions of lifetimes may be considered ... 

In the majority of cases, fluorescent labels and probes, when studied in different liquid solvents, display single-exponential fluorescence decay kinetics. However, when they are bound to proteins, their emission exhibits more complicated, nonexponential character. Thus, two decay components were observed for the complex of 8-anilinonaphthalene-l-sulfonate (1,8-ANS) with phosphorylase(49) as well as for 5-diethylamino-l-naphthalenesulfonic acid (DNS)-labeled dehydrogenases.(50) Three decay components were determined for complexes of 1,8-ANS with low-density lipoproteins.1 51 1 On the basis of only the data on the kinetics of the fluorescence decay, the origin of these multiple decay components (whether they are associated with structural heterogeneity in the ground state or arise due to dynamic processes in the excited state) is difficult to ascertain. 

The time-resolved emission spectra were reconstructed from the fluorescence decay kinetics at a series of emission wavelengths, and the steady-state emission spectrum as described in the Theory section (37). Figure 4 shows a typical set of time-resolved emission spectra for PRODAN in a binary supercritical fluid composed of CO2 and 1.57 mol% CH3OH (T = 45 °C P = 81.4 bar). Clearly, the emission spectrum red shifts following excitation indicating that the local solvent environment is becoming more polar during the excited-state lifetime. We attribute this red shift to the reorientation of cosolvent molecules about excited-state PRODAN. 

Siemiarezuk and Ware l have reinvestigated the fluorescence decay kinetics of 1,2-di(1-pyrenyl)propane and concluded in contradiction to previous reports, that there is a distribution of short lifetimes in addition to two longer lived fluorescence components. This proposal has produced a strong dissent by Zachariasse and Striker 23 vvho on the basis of a global analysis, maintain that only three decays are observed, namely two excimer emissions and one from the monomer. 

D. L. Akins, S. Oz9elik, H. Zhu, C. Guo, Fluorescence decay kinetics and structure of aggregated tetrakis(p-sulfonatophenyl)porphyrin, J. Chem. 100,14390-14396(1996). 

KK Karukstis and K Sauer (1983) Fluorescence decay kinetics of chlorophyll in photosynthetic membranes. J Cell Biochem 23 131-158... 

The formation of intreunolecular excimers in polymer systems has aroused much interest in recent years (1). Perhaps most notable is the general observation that the reaction kinetics do not obey the accepted Birks scheme for low molecular weight systems (2)- In this scheme the fluorescence decay kinetics of the monomer (M) eind excimer (D) species Ccui be separated spectrally with fluorescence response functions of the form... 

Spectral equihbration occurs within the antenna in less than 5 ps and leads to a state characterized as a transfer equilibrium state, rather than a thermodynamic equilibrium state. By this we mean that single exponential fluorescence decay kinetics are observed at all detection wavelength on timescales longer than 5 ps. 

Fig. 4.6 The fluorescence decay kinetics of bovine rhodopsin (A), protonated Schiff base of 11-c/s-retinal (PSB11) in methanol (B), and protonated Schiff base of5-membered locked 11 -c/s retinal (5m-PSBll) in methanol (C). The data in (A) are from Kandori et al. [52], while those in (B) and (C) are from Kandori...

Beechem describes a second generation global analysis program for the recovery of complex inhomogeneous fluorescence decay kinetics. 

The complexity observed in polymer fluorescence decay kinetics is further exacerbated when fluorescent polyelectrolytes are dissolved in aqueous media [29,30,33,35,37,43,120,122,128-132] segregation of the macromolecular structure into hydrophobic and hydrophilic-rich domains results in differing degrees of water penetration which further complicates the time-resolved fluorescence [26]. Within this context, more recent attempts to describe time-resolved polymer photophysical data include use of the blob model [133,134], which accounts for the range of environments encountered in heterogeneous systems by invoking a distribution of rate constants for excimer formation. 

In the simplest case of a single type of fluorescing chromophore being depopulated by various processes, the relationships determining the fluorescence decay kinetics and their relation to steady-state parameters are given by the following equations. The excited state decay is given by a first-order differential equation ... 

Lakowicz, J. R., Cherek, H., Gryezynski, I., Joshi, N., and Johnson, M. L., 987, Analysis of fluorescence decay kinetics measured in the frequency domain using disttibution of decay times. Biophys. Chem. 28 35-50. 

Beec tem, J. M.. 1989, A second genention global anal pro gram for die recovery of complex inhomogeneous fluorescence decay kinetics, Chem. Pl. Lipids SOiZyt-251. 

Table 1. Fluorescence decay kinetics and AG(P680+Ph"-P680 ) values for D1/D2 reaction centres over the temperature range 277 K to 77 K. and are the charge...

---