Fluorescence intensity, magnitude

In summary, the encapsulation of cyanine dyes in CB7 causes either an increase or a decrease in quantum yields and brightness but in general increases photostability. Enhancements in fluorescence intensity by about one order of magnitude or more were observed [46]. These fluorescence property changes are utilized for the development of sensors, where the fluorescent dye may serve as a probe to signal the binding of an analyte. No reports were found on the encapsulation of squaraines in CBs. 

Ho et al. were able to verify the a-helical shape of the polymer by circular dichroism (CD) spectra. No structural elements were observed until the formation of the double helical DNA at which point they observed a right-handed a-helix in the polythiophene backbone. Their work demonstrates the power of fluorometric detection as they noted a seven order of magnitude increase in detection sensitivity (20 fM in 200 pi) simply through the use of fluorometric detection as opposed to UV-vis absorption. The polymer in solution has a high fluorescence yield with a maximum at 530 nm (Fig. 11a). Upon formation of the duplex the fluorescence is significantly quenched (Fig. lib), while with the addition of the complementary DNA and triplex formation, the fluorescence intensity is enhanced by a factor of 5 (Fig. 11c). The inherent sensitivity of the spectral shift even allowed distinction between DNA with only one and two mismatched bases (Fig. lOBd, e). 

Fig. 3. Schematic diagram of the spot photobleaching method of FRAP. (A) Darkened circles represent fluorescently labeled molecules evenly distributed over a two-dimensional surface (assumed to be an infinite plane). (B) White and light gray circles represent the initial postbleach distribution of photobleached molecules within a 1-pm diameter spot. (C) Redistribution of photobleached and unbleached molecules as a consequence of random diffusion over time. (D) Curve representing the fluorescence intensity within the l-pm diameter spot monitored over time arrows a, b, and c indicate the time-points that correspond to their respective panels. The rate of recovery from point b to point c is used to determine the diffusion constant. The magnitude of the recovery is determined by comparing the fluorescence intensity at point c with the initial intensity at point a, and is used to determine the mobile fraction.

In measurements at such low pressures the fluorescence intensity is several orders of magnitude smaller than the primary light inevi-... 

In order to describe a signal by this method we will first use the classical approach. At the beginning we will ascertain how either probability density Pb(9, multipole moments ipq of the excited state 6, entering into the fluorescence intensity expressions (2.23) or (2.24), are connected to the corresponding magnitudes pa(9, ground state a. The respective kinetic balance equation for probability density and its stationary solution, assuming that the conditions supposed to hold in Eq. (3.4) are in force, is very simple indeed ... 

A series of computations based on observation of NAD(P)H fluorescence in single living cells under strong 366 nm excitation suggests that the order of magnitude of the fluorescence intensity constant K in the maximum of the fluorescence band at 470 nm is ... 

Iron K-edge EXAFS experiments were also performed on the Na,K(Fe) chabazlte and H(Fe) chabazlte samples. The experimental spectra were obtained at room temperature both In transmission and fluorescence mode at the Stanford Synchrotron Radiation laboratory. Because of the dilution of Fe in the hosts, the fluorescence data were an order of magnitude better In statistics than the absorption data. Multiple runs were taken on each sample, and the Incident and fluorescent Intensities, IQ and If, were summed respectively to Improve the signal-to-noise ratio. 

This latest expression provides in addition the magnitude of the fluorescence intensity enhancement factor at a given frequency CO. In some... 

Figure 1.3. Energy levels associated with 514.5 and 785 nm light incident on a fluorescent sample. Energy and intensity scales are not to scale, and fluorescence intensity is several orders of magnitude greater than Raman scattering. Raman shift axis is relative to the incident laser frequency.

The magnitude of threshold concentration Q and the constant K are specific to each fluorescent substance. The threshold concentration is determined from the concentration dependence of the luminescence intensity. In dilute solutions, the fluorescence intensity (I) is a linear function of concentration ... 

---