Fluorescent transfer using SAED

The observation of selective fluorescence quenching by G C base pairs is consistent with the energetics of electron transfer (charge separation) from the bases to the singlet excited state Sa, which can be estimated using Weller s equation [26] ... 

Figure 5.27 SAED may be used to transfer the fluorescent AMCA label from the first molecule modified with the crosslinker to the second molecule crosslinked with it by reduction of its internal disulfide bond. Thus, unknown target molecules may be fluorescently tagged to follow them in vivo.

Another crosslinker, SAED (Chapter 5, Section 3.9), can be used in a similar fashion, but instead of transferring a radioactive label, it contains a fluorescent portion that is transferred to a binding molecule after cleavage. Similarly, sulfo-SBED routinely is used to study protein interaction. Cleavage of a disulfide bridge after capture of interacting proteins results in transfer of a biotin label to the unknown prey protein (Chapter 28, Section 3.1). The biotin modification then can be used to detect or isolate the unknown interactor for subsequent identification. 

Another cross-linker, SAED (Chapter 5, Section 3.9), can be used in a similar fashion, but instead of transferring a radioactive label, it contains a fluorescent portion that is transferred to a binding molecule after cleavage. 

The photophysics of solid salicylic acid (SA) has been studied by using steady-state and time-resolved spectroscopic techniques [207,208], Dimers of SA form in two possible structures (59 and 60) due to fast ground-state double proton transfer. Dual fluorescence is observed at 380 nm and 440 nm, which are ascribable to the excited-state double proton transfer between different dimeric structures of SA. The enol form is more stable in the ground state. However, in the excited singlet state, the keto form has a lower potential energy [207], This excited enol-keto tautomerism has a barrier height of -1250 cm as is calculated from the dependence of dual fluorescence on excitation wavelength in the... 

The energy E in Equation 6.86 has been replaced by the frequency v (in cm-1), FA E) has been replaced by the extinction coefficient sA v) of the acceptor, (pp is the fluorescence quantum yield, and k2 2/3 is an orientation factor. An expression similar to Equation 6.87 was deduced by Foster using a simpler mechanism of the energy transfer.41 The rate constant deduced from the dipole-quadmpole interaction is given in Equation 6.88, where a 1.266 and other parameters and functions are as defined above. 

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