Anisotropy, of fluorescence

Let us consider tire case of a donor-acceptor pair where tire acceptor, after capturing excitation from tire donor, can emit a photon of fluorescence. If tire excitation light is linearly polarized, tire acceptor emission generally has a different polarization. Common quantitative expressions of tliis effect are tire anisotropy of fluorescence, r, or tire degree of polarization,... 

Figure 8.11 (a) Fluorescence (dotted line) and fluorescence excitation spectra (b) anisotropy of fluorescence excitation of 1 (A) and 1e (B). Both samples were measured at 113 Kin 1-propanol glass. In the excitation spectra, the emission was monitored atl5900cm (1) and atl4900cm" (1e). 

Figure 8.15 (a) Steady state anisotropy of fluorescence excitation of 1 recorded in poly(vinyl butyral) film as a function of temperature. The spectra were taken at 293, 250, 215, 165, 125, 85, 65, 45, and 7.5 K. (b) The excitation spectrum at 85 K monitored at 15900cm . ... 

It is instructive to compare the significance of results obtained in studies using the emission anisotropy of fluorescent labels and medium sensitive labels to monitor polymer association. In the first case the results reflect the rotational diffusion constant of the labeled species which is reduced when a polymer complex is formed but would not be expected to be sensitive to the nature of the association. With the second technique we sample the microenvironment of the label, so that a loose and a tight association can be distinguished. This enabled us to demonstrate the swelling of the PAA-PVP complex when the pH was raised and to show that that the nature of the PAA-POE complex depends on the molecular weight of the POE. 

Lee, J., Wang, Y., and Gibson, B. G. (1990). Recovery of components of fluorescence spectra of mixtures by intensity- and anisotropy decay-associated analysis the bacterial luciferase intermediates. Anal. Biochem. 185 220-229. 

The fluorescence depolarization technique excites a fluorescent dye by linearly polarized light and measures the polarization anisotropy of the fluorescence emission. The fluorescence anisotropy, r, is defined as... 

Fluorescence polarization anisotropy of a ligand and its complexes with DNA or RNA can be given by the following expression ... 

Figure 5. Fluorescence anisotropy of F-D labelled heparin-antithrombin interaction. F-D-heparin (0.02 fluoresceins per uronic acid) at 0.1 mg/ml was incubated with different concentrations of antithrombin (open circles) or bovine serum albumin (solid diamonds) in 20 mM sodium phosphate buffer, pH 7.4.

Comparative Analysis of Fluorescence Reporter Signals Based on Intensity, Anisotropy, Time-Resolution,... 

Abstract The response signal of an immense number of fluorescence reporters with a broad variety of structures and properties can be realized through the observation in changes of a very limited number of fluorescence parameters. They are the variations in intensity, anisotropy (or polarization), lifetime, and the spectral changes that allow wavelength-ratiometric detection. Here, these detection methods are overviewed, and specific demands addressed to fluorescence emitters for optimization of their response are discussed. 

Anisotropy describes the rotational dynamics of reporter molecules or of any sensor segments to which the reporter is rigidly fixed. In the simplest case when both the rotation and the fluorescence decay can be represented by single-exponential functions, the range of variation of anisotropy (r) is determined by variation of the ratio of fluorescence lifetime (xF) and rotational correlation time ([Pg.9]

Demchenko AP (2010) Comparative analysis of fluorescence reporter signals based on intensity, anisotropy, time-resolution and wavelength-ratiometry. In Demchenko AP (ed) Advanced Fluorescence Reporters in Chemistry and Biology I. Springer Ser Fluoresc 8 3-24... 

Before being able to study the nonlinear optical properties of any material, it is necessary to have a complete understanding of its linear optical properties. Therefore, we start this section with a brief discussion of the techniques used to measure some of the most important linear properties, e.g., linear absorption, fluorescence, anisotropy, and fluorescence quantum yield. 

Dependencies of luminescence bands (both fluorescence and phosphorescence), anisotropy of emission, and its lifetime on a frequency of excitation, when fluorescence is excited at the red edge of absorption spectrum. Panel a of Fig. 5 shows the fluorescence spectra at different excitations for the solutes with the 0-0 transitions close to vI vn, and vra frequencies. Spectral location of all shown fluorescence bands is different and stable in time of experiment and during lifetime of fluorescence (panel b)... 

One of the most popular applications of molecular rotors is the quantitative determination of solvent viscosity (for some examples, see references [18, 23-27] and Sect. 5). Viscosity refers to a bulk property, but molecular rotors change their behavior under the influence of the solvent on the molecular scale. Most commonly, the diffusivity of a fluorophore is related to bulk viscosity through the Debye-Stokes-Einstein relationship where the diffusion constant D is inversely proportional to bulk viscosity rj. Established techniques such as fluorescent recovery after photobleaching (FRAP) and fluorescence anisotropy build on the diffusivity of a fluorophore. However, the relationship between diffusivity on a molecular scale and bulk viscosity is always an approximation, because it does not consider molecular-scale effects such as size differences between fluorophore and solvent, electrostatic interactions, hydrogen bond formation, or a possible anisotropy of the environment. Nonetheless, approaches exist to resolve this conflict between bulk viscosity and apparent microviscosity at the molecular scale. Forster and Hoffmann examined some triphenylamine dyes with TICT characteristics. These dyes are characterized by radiationless relaxation from the TICT state. Forster and Hoffmann found a power-law relationship between quantum yield and solvent viscosity both analytically and experimentally [28]. For a quantitative derivation of the power-law relationship, Forster and Hoffmann define the solvent s microfriction k by applying the Debye-Stokes-Einstein diffusion model (2)... 

Fixler, D., Namer, Y., Yishay, Y. and Deutsch, M. (2006). Influence of fluorescence anisotropy on fluorescence intensity and lifetime measurement theory, simulations and experiments. IEEE Trans. Biomed. Eng. 53, 1141-52. 

UV Absorption, Fluorescence Spectra, and Fluorescence Anisotropy of Optically Inactive Homopolymers... 

The chromophore environment can affect the spectral position of the absorption and emission bands, the absorption and emission intensity (eM, r), and the fluorescence lifetime as well as the emission anisotropy, e.g., in the case of rigid matrices or hydrogen bonding. Changes in temperature typically result only in small spectral shifts, yet in considerable changes in the fluorescence quantum yield and lifetime. This sensitivity can be favorably exploited for the design of fluorescent sensors and probes [24, 51], though it can unfortunately also hamper quantification from simple measurements of fluorescence intensity [116], The latter can be, e.g., circumvented by ratiometric measurements [24, 115],... 

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