Intensity trajectories

Figure 17.12 (A) Schematic presentation of deactivation and energy transfer processes in a single quantum dot placed on an Ag nanoparticle film. (B) Photoluminescence intensity trajectories of single quantum dots on a glass substrate (a) and on an Ag nanoparticle film (b). The traces in green represent background intensities. (C) Photoluminescence spectra of quantum dot solutions in the presence of...

Figure 2. Distributions / (t) of on and off times for the NC, whose intensity trajectory is shown in Fig. 1. The straight line is the fit to the off time distribution.

In the limit of long times and if the ergodic assumption holds, then we have 7 = (/), where (I) is the ensemble average. As usual, we may generate many intensity trajectories one at a time, to obtain the ensemble-averaged correlation function... 

Figure 14. Histograms of relative on times 7 1 /7 for 100 experimental (left) and 100 simulated (right) intensity trajectories, for different T. ...

Figure 24.2a shows dual fluorescence intensity trajectories simultaneously recorded from a donor-acceptor labeled T4 lysozyme in the presence of substrate at pH 7.2. The anticorrelated fluctuations (Fig. 24.2a and b) are due to spFRET, reporting the donor-acceptor distance change associated with the protein conformational motion. Likewise, fluorescence trajectories of donor-acceptor labeled T4 lysozyme without substrates did not show anticorrelated behavior (Fig. 24.2c and d). We attribute this conformational motion to an enzymatic-related motion, most likely the open-closed hinge-bending motion... 

The fluorescence intensity trajectories of the donor (/d(f)) and acceptor (/a(t)) give autocorrelation times (Fig. 24.2b) indistinguishable from fitting an exponential decay to the autocorrelation functions, (A/d (0) A/d (t)) and (A/a (0) A/a (t)), where A/d(t) is /d(t) — (Id), (Id) is the mean intensity of the overall trajectory of a donor, and A/a(t) has the same definition for an intensity trajectory of an acceptor. In contrast, the cross-correlation function between the donor and acceptor trajectories, (A/d (0) A/d (t)), is anticorrelated with the same decay time (Fig. 24.2b) which supports our assignment of anticorrelated fluctuations of the fluorescence intensities of the donor and acceptor to the spFRET process. 

To characterize the binding and the motions of the placed single T4 lysozyme molecules on cell walls, we used single-molecule fluorescence polarization measurements. The orientation of the single-molecule transition dipole can be probed by either linear polarized excitation or linear polarized emission. In this work, the excitation light was unpolarized. The emission was split into orthogonal (s polarized /i and p polarized I2) polarizations and detected by two photon detectors [22]. The intensity trajectories probed at the two orthogonal polarizations are shown in Fig. 24.9c (upper panel). The polarization P is defined as ... 

Figure 1 (a) Catalytic cycle of COx. E enzyme, (b) Fluorescence intensity trajectory of a single COx molecule during catalysis, (c) Distribution of the on-times (bars) derived from... 

Figure 5 (a) The structure of T4 lysozyme with the two dye labels schematically shown, (b) Fluorescence intensity trajectories of the TM R donor (blue) and the Texas Red acceptor (red) of a single T4 lysozyme in the presence of E coli B cell wall, (c) Distribution of the decay rate constants (/t) of the donor intensity autocorrelation functions. Reproduced with permission from Y. Chen D. Hu E. R. Vorpagel H. P. Lu, J. Phys. Chem. B. 2003,107, 7947-7956. Copyright (2003) American... 

Information contained in fluorescence intensity trajectories from single molecules... 

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