Photobleaching process

CYlionic nicthine dye u.sed to 1002 ohtaln positive colored image in an Ag-free photobleaching process... 

In the microscopic technique, photobleaching FRET (5), the intensity of fluorescence excitation is increased to cause photobleaching of the donor fluorochrome, and the decay kinetics are measured in the absence or presence of an acceptor fluorochrome. If the acceptor is in close proximity to the donor, then the availability of excited-state donors for photobleaching is reduced, thus making the photobleaching process slower. 

The quantum yields and kinetics of the photobleaching of these compounds were determined, and their thermal coloration rates and activation energies were measured. The pH dependence of the spectral absorption changes, due to both the shift in the position of the protonation equilibrium between the spiro form and its salt, and the equilibrium between the salts of the spiro form and the open form, were also measured. A detailed analysis of the extensive data led to the spectroscopic identification of the short-lived ground-state cis conformers of the open forms of the five compounds studied. The photobleaching process is a photo trans-cis isomer-... 

The absorption band (Amax 488 nm) in the transient spectrum corresponds to the pyrene radical ion (Py ) [155, 156], while the band at Amax 400 nm is assigned to the absorption of the 1-hydro-1-pyrenyl radical (Py ) [157, 158]. Steady-state photolysis of pyrene in the presence of TEA leads to its disappearance, and addition of vinyl monomers decreases the rate of pyrene photoreduction. The photobleaching process follows first-order kinetics. Encinas et al. [154] suggest that the photoinitiation of polymerization by pyrene-TEA is catalyzed by the pyrene radical ion. 

Watanabe O, Tsuchimori M, Okada A. 1996. Two step refractive index changes by photoisomerization and photobleaching processes in the films of nonlinear optical polyurethanes and a urethane urea copolymer. J Mater Chem 6(9) 1487 1492. 

FIGURE 125.3 Photobleaching process of bovine rhodopsin. The times denoted at the right-hand side of the arrows are decay time constants of the intermediates. The absorption maxima of rhodopsin and its intermediates are shown in parentheses. 

Shichida, Y., Kandori, H., Okada, X., Yoshizawa, X., Nakashima, N., and Yoshihara, K., Differences in the photobleaching process between 7-cis- and 11-c/s-rhodopsins a unique interaction change between the chromophore and the protein during the lumi-meta 1 transition. Biochemistry, 30, 5918, 1991. 

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