Anisotropy decay

Cross A J and Fleming G R 1984 Analysis of time-resolved fluorescence anisotropy decays Blophys. J. 46 45-56... 

DIffey W M, Homoelle B J, Edington M D and Beck W F 1998 Excited-state vibrational coherence and anisotropy decay In the bacterlochlorophyll a dimer protein B820 J. Phys. Chem. B 102 2776-86... 

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. 

Energy hopping among the peryleneimide chromophores, revealed by anisotropy decay times [30], occurs with a rate constant of 4.6x10 s E When three peryleneimide and one terryleneimide chromophores are attached to the dendrimer rim, energy transfer from the former to the latter units takes place with... 

Figure 4.7 Fluorescence anisotropy decay curves for the PMMA brush swollen in benzene (filled circles) and the free PMMA chain in benzene solution at concentrations of 0.33 (triangles) and 2.9 X 10 g (open circles). The graft density of the brush is 0.46 chains nm . The solid curve indicates the instrument response function. Reproduced with permission from the American Chemical Society.

Figure 4.8 shows the fluorescence anisotropy decay curves for PMMA brushes with various graft densities swollen in benzene and acetonitrile. Benzene and acetonitrile are good and 0 solvents for PMMA. As clearly shown in this figure. 

Figure 4.9 Correlation time of the fluorescence anisotropy decay for the PMMA brush. The open and closed circles indicate the correlation times for the brush in acetonitrile and benzene, respectively.

Figure 4.12 Fluorescence image of PMMA brush layer (a) and schematic drawing of the brush chain (b). The dark region (a) corresponds to the substrate surface exposed by scratching off the brush layer. The filled and open circles indicate the points where the fluorescence anisotropy decay was acquired.

FIG. 11 Order parameter variation along acyl chains in red cell ghosts ( ), small unilamellar vesicles of egg phosphatidylcholine (V), and paraffin oil (+), as determined by the fluorescence anisotropy decay of the w-anthroyloxy fatty acid probes. (Reprinted by permission from Ref. 12.)... 

Borst JW, Flink MA, van Hoek A, Visser AJWG (2005) Effects of refractive index and viscosity on fluorescence and anisotropy decays of enhanced cyan and yellow fluorescent proteins. JFluoresc 15 153-160... 

Volkmer, A., Subramaniam, V., Birch, D. J. and Jovin, T. M. (2000). One- and two-photon excited fluorescence lifetimes and anisotropy decays of green fluorescent proteins. Biophys. J. 78, 1589-98. 

Fisz, J. J. (2007). Another look at magic-angle-detected fluorescence and emission anisotropy decays in fluorescence microscopy. J. Phys. Chem. A 111, 12867-70. 

Tleugabulova, D., Duft, A.M., Zhang, Z., Chen, Y., Brook, M.A. and Brennan, J.D. (2004) Evaluating formation and growth mechanisms of silica particles using fluorescence anisotropy decay analysis. Langmuir, 20, 5924—5932. 

Photon echo and IR pump-probe experiments can also be performed on neat water, but one needs a very small sample. Fabrication of nano-fluidic Si3Ni4 sample cells have opened up this new and exciting field, and data from these experiments, performed by the Elsaesser and Miller groups, have recently been reported [73, 74]. At room temperature, spectral evolution occurs within 50 fs, and polarization anisotropy decays within 75 fs. At temperatures just about the freezing point, spectral evolution slows down dramatically [74],... 

Theoretical calculations for ultrafast neat water spectroscopy are difficult to perform and difficult to interpret (because of the near-resonant OH stretch coupling). One classical calculation of the 2DIR spectrum even preceded the experiments [163] Torii has calculated the anisotropy decay [97], finding reasonable agreement with the experimental time scale. Mixed quantum/ classical calculations of nonlinear spectroscopy for many coupled chromo-phores is a daunting task. We developed the TAA for linear spectroscopy, and Jansen has very recently extended it to nonlinear spectroscopy [164]. We hope that this will allow for mixed quantum/classical calculations of the 2DIR spectrum for neat water and that this will provide the context for a molecular-level interpretation of these complex but fascinating experiments. 

Fast librational motions of the fluorophore within the solvation shell should also be consideredd). The estimated characteristic time for perylene in paraffin is about 1 ps, which is not detectable by time-resolved anisotropy decay measurement. An apparent value of the emission anisotropy is thus measured, which is smaller than in the absence of libration. Such an explanation is consistent with the fact that fluorescein bound to a large molecule (e.g. polyacrylamide or monoglucoronide) exhibits a larger limiting anisotropy than free fluorescein in aqueous glycerolic solutions. However, the absorption and fluorescence spectra are different for free and bound fluorescein the question then arises as to whether r0 could be an intrinsic property of the fluorophore. 

A distinction should be made between free rotation and hindered rotation. In the case of free rotation, after a (5-pulse excitation the emission anisotropy decays from ro to 0 because the rotational motions of the molecules lead to a random orientation at long times. In the case of hindered rotations, the molecules cannot become randomly oriented at long times, and the emission anisotropy does not decay to zero but to a steady value, r (Figure 5.10). These two cases of free and hindered rotations will now be discussed. 

In principle, the shape parameters of asymmetric rotors can be estimated from time-resolved anisotropy decay measurements, but in practice it is difficult to obtain accurate anisotropy decay curves over much more than one decade, which is often insufficient to determine more than two rotational correlation times. 

It is interesting to note that rc(l — r.y,/r0) is exactly the area A under [r(t) — r, /ro. Therefore, even if the anisotropy decay is not a single exponential, Dw can be determined by means of Eq. (5.50) in which tc(1 — roo/ro) is replaced by the measured area A. An example of application of the wobble-in-cone model to the study of vesicles and membranes is given in Chapter 8 (Box 8.3). More general theories have also been developed (see Box 5.4). 

The diffusion constant D with the underlying microviscosity , and the two order parameters , <(P4> reflecting the degree of orientational constraint have been successfully determined from the fluorescence anisotropy decay in... 

Lipid-protein interactions are of major importance in the structural and dynamic properties of biological membranes. Fluorescent probes can provide much information on these interactions. For example, van Paridon et al.a) used a synthetic derivative of phosphatidylinositol (PI) with a ris-parinaric acid (see formula in Figure 8.4) covalently linked on the sn-2 position for probing phospholipid vesicles and biological membranes. The emission anisotropy decays of this 2-parinaroyl-phosphatidylinositol (PPI) probe incorporated into vesicles consisting of phosphatidylcholine (PC) (with a fraction of 5 mol % of PI) and into acetylcholine receptor rich membranes from Torpedo marmorata are shown in Figure B8.3.1. 

Fig. B8.3.1. Fluorescence anisotropy decays at 4 °C of PPL A in phospholipid vesicles (PC PI, 95 5 mol %). B in Torpedo membranes. From the best fit of the /(t) and l (t) components, and by using the wobble-in-cone model, the...

Such is the newness of appreciation of near-IR fluorescence techniques that there is a dearth of examples in the literature of implementations of many of the classic fluorescence methods in the IR. Anisotropy is one striking example of this. However, in a comprehensive study of the anisotropy decay of dyes, including oxazine fluorescence at 720 nm, in mixed isotropic solvents Dutt et al.( T7 TS) have investigated the effects of viscosity on molecular rotation. 

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