Steady-State and Time-Resolved Fluorescence

Equations [1.13] and [1.14] can be used to illustrate how the decay time determines what can be observed using fluorescence. The steady-state anisotropy (r) is given by the average of r(0 wei ted by 7(0  

In this equation Ae denominator is presoit to normalize die anisotropy to be independent of total intensity, hi die niimaator the anisotropy at any time t contributes to die steady-stale anisotropy according to the intensity at time t. Substitution of Eqs. [1.13] and [1.14] intoEq. [1 15] yields the Poinn equaticNi (Eq. [1.10]). 

PMtuqis a sim da example is how die stearfy-state ioten-sity Iss is idated to the decay time. The steady-state intenaty is given by 

The value of /o can be considered to be a parametM vhidi depends on the fluorophore concentration and a number of instrumenta] parametos. Hence, in mdecular terms, the steady-state intensity is proportional to the lifetime. This 

Whereas steady- tate flucvesceoce measuimiMts are im pie, nanoscoond time-res 4ved measuremeDts ty]Ncally re quire and expulsive instnimeotation. Given the 

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The application of semiconductor lasers to a broad range of areas in spectrometry has recently been reviewed by Imasaka. 67, 68) Topics covered include photoacoustic, absorption, and thermal lens, as well as steady-state and time-resolved fluorescence. Patonay et al. have reviewed the application of diode lasers to analytical chemistry.(69) The performance of several commercially available laser diodes for fluorimetry has recently been compared. 70 ... 

Photodiodes occur in many different varieties and are useful in both steady-state and time-resolved fluorescence studies. Photodiodes designed for use in steady-state or on microsecond time-scales are inexpensive and have effective areas up to a few square millimeters, and are capable of efficiently matching to simple focusing optics. However, as the temporal resolution increases so does the cost, and the effective area has to be reduced. For example, APDs with response times in the 50 psec region have effective diameters ofca. 10 /small active area of high-speed devices is currently the primary drawback in fluorescence studies. Also, photodiodes other... 

Permyakov et alS32) have compared the effects of calcium binding upon the steady-state and time-resolved fluorescence of two different species of fish parvalbumin, one with a single tryptophan (whiting) and one with a single tyrosine (pike). The fluorescence decays of both proteins were best fit by double exponentials either in the presence or absence of calcium. We focus here on the tyrosine results from pike parvalbumin. Calcium binding causes a 50% increase in the tyrosine steady-state fluorescence quantum yield and... 

C. A. Hasselbacher, E. Waxman, L. T. Galati, P. B. Contino, J. B. A. Ross, and W. R. Laws, Investigation of hydrogen bonding and proton transfer of aromatic alcohols in non-aqueous solvents by steady-state and time-resolved fluorescence, J. Phys. Chem. 95, 2995-3005 (1991). 

E. A. Permyakov, A. V. Ostrovsky, E. A. Burstein, P. G. Pleshanov, and C. Gerday, Parvalbumin conformers revealed by steady-state and time-resolved fluorescence spectroscopy, Arch. Biochem. Biophys. 240, 781-791 (1985). 

C. D. Stubbs, K. Kinosita, Jr., F. Munkonge, P. J. Quinn, and A. Ikegami, The dynamics of lipid motion in sarcoplasmic reticulum membranes determined by steady-state and time-resolved fluorescence measurements on l,6-diphenyl-l,3,5-hexatriene and related molecules, Biochim. Biophys. Acta 775, 374-380 (1984). 

M. Vincent, J. Gallay, J. de Bony, and J.-F. Tocanne, Steady-state and time-resolved fluorescence anisotropy study of phospholipid molecular motion in the gel phase using l-palmitoyl-2-[9-(2-anthryl)-nonanoyl]-sn-glycero-3-phosphocholine as probe, Ear, J. Biochem. 250, 341-347 (1985). 

A Steady-State and Time-Resolved Fluorescence Study of Quenching Reactions of Anthracene and 1,2-Benzanthracene by Carbon Tetrabromide and Bromoethane in Supercritical Carbon Dioxide (Zhang et al., 1997)... 

Various mechanisms for the photoinduced geometrical isomerization of 9-styrylanthracenes have been proposed recently [90-93]. From steady-state and time-resolved fluorescence measurements on the parent 9-styrylanth-racenes 68a/69a and their formyl and 4-phenylsulfonyl derivatives (681/691 68j/69j), it has been concluded that the geometrical isomerization is an adiabatic process which occurs both in the excited singlet and triplet states [90]. Thus, for the conversion of the parent cis compound 68a into 69a, 85%... 

Elucidation of Solute—Fluid Interactions in Supercritical CF H by Steady-State and Time-Resolved Fluorescence Spectroscopy... 

We report on steady-state and time-resolved fluorescence of pyrene excimer emission in sub- and supercritical C02. Our experimental results show that, above a reduced density of 0.8, there is no evidence for ground-state (solute-solute) interactions. Below a reduced density of 0.8 there are pyrene solubility complications. The excimer formation process, analogous to normal liquids, only occurs for the excited-state pyrene. In addition, the excimer formation process is diffusion controlled. Thus, earlier reports on pyrene excimer emission at rather "dilute pyrene levels in supercritical fluids are simply a result of the increased diffusivity in the supercritical fluid media. There is not any anomalous solute-solute interaction beyond the diffusion-controlled limit in C02. 

In this paper, we present a preliminary analysis of the steady-state and time-resolved fluorescence of pyrene in supercritical C02. In addition, we employ steady-state absorbance spectroscopy to determine pyrene solubility and determine the ground-state interactions. Similarly, the steady-state excitation and emission spectra gives us qualitative insights into the excimer formation process. Finally, time-resolved fluorescence experiments yield the entire ensemble of rate coefficients associated with the observed pyrene emission (Figure 1). From these rates we can then determine if the excimer formation process is diffusion controlled in supercritical C02. 

This simple RNA stemloop serves as an illustration of how both steady-state and time-resolved fluorescence together provide a detailed description of the properties of an RNA (Hall and Williams, 2004). The sequence of the iron response element (IRE) RNA hairpin loop [C6A7G8U9G10C11] is phylogenetically conserved (numbered from our construct). Cytidine 6 and... 

Steady-state and time resolved fluorescence used to examine proton transfer Solubilization in anionic micelles was examined in various conditions... 

Molecular assemblies in anionic environments influence the efficiency of fluorescence quenching by electron transfer . Viseu and Costa use a combination of steady state and time resolved fluorescence quenching data to evaluate partition coefficients of fluorescent molecules into micelles. The breakdown of rod-like micelles and light induced viscosity changes in micelles are effects that can both be induced by isomerization of azo-compounds in a variety of surfactants. ... 

An unusual example of delayed fluorescence exemplifying El Sayed s rules (Section 2.1.6) was recently reported for the triplet sensitizer xanthone,127 which undergoes ultrafast ISC within 1 ps. Delayed fluorescence with a lifetime of 700 ps was observed in aqueous solution. Temperature-dependent steady-state and time-resolved fluorescence experiments indicate that the T2(n,it ) state, which is primarily accessed by ISC from Si(ji,ji ), is nearly isoenergetic with the Sj state. The delayed fluorescence is attributed to reverse ISC from T2(n,it ), in competition with internal conversion to Tl(7I,7l ). 

The spectroscopy and dynamics of the excited state double proton transfer in 2-amino-4,6-dimethylpyrimidine and 2-amino-4-methoxy-6-methylpyrimidine has been studied by steady-state and time-resolved fluorescence spectroscopy (01CP(265)233). 

The tautomerism of 2-(3,-hydroxy-2,-pyridyl)benzimidazole 215 in the ground and first excited singlet states in various solvents has been investigated by UV-vis absorption spectroscopy, by steady-state and time-resolved fluorescence spectroscopy, and by semiempirical AMI and ab initio RHF calculations. In the ground state, the tautomeric equilibrium 215a 215b was observed, the equilibrium shifting toward... 

Anilinonaphthalene-6-sulfonic acid, 4, complexation with /S- or y-CD in the presence of alcohols was studied using steady-state and time-resolved fluorescence spectroscopy [62]. The /5-CD-4 fluorescence was decreased by... 

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