T/Q ratio

Equation (11.9) indicates the possibility of calculating the rotational correlation time of the fluorophore not only by varying the T/q ratio but also by adding a collisional quencher. Interaction between the quencher and fluorophore decreases the fluorescence lifetime and intensity of the fluorophore, and increases its fluorescence anisotropy. Plotting 1 /A as a function of r0 yields a straight line with a slope equal to r. If the fluorophore is tightly bound to the macromolecule and does not exhibit any residual motions, the measured 0r is equal to, and the extrapolated anisotropy is equal to that measured at a low temperature. 

The spectra of the samples prepared in the presence of PTMOS look quite different from each other. At a synthesis temperature of 25 °C, the appearance of T peaks indicates that the phenylsiloxy residues have become incorporated very effectively (T [RSiOs] unit attached to one other silicon atom, appears at ca. -61 ppm 7 [RSiOa] unit attached to two other silicon atoms, ca. -71 ppm 7 [RSiOa] unit attached to three other silicon atoms, ca. -79 ppm). The ratio of the T.Q signals is ca. 1 3 for this sample. On the other hand, for the sample synthesized at 110 °C, T signals are hardly visible, and a quantitative evaluation gives a T.Q ratio of ca. 1 12. Obviously, the phenylsiloxy residues have become incorporated into the silica walls only to a very small degree. 

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