Fluorescent Molecular Switches

Li, B. L., Wei, H., Dong, S. J. (2007a). Sensitive detection of protein by an aptamer-based label-free fluorescing molecular switch. Client Commun 13-15. 

Figure 6.20 Action of a fluorescent PET potassium cation sensor as a molecular switch using a macrocyclic electron donor and anthracene fluorophore...

Mangano C. (1998) Molecular Switches of Fluorescence Operating Through Metal Centred Redox Couples, Coord. Chem. Rev. 170, 31-46. 

Switching systems based on photochromic behavior,I29 43,45 77-100 optical control of chirality,175 76 1011 fluorescence,[102-108] intersystem crossing,[109-113] electro-chemically and photochemical induced changes in liquid crystals,l114-119 thin films,170,120-1291 and membranes,[130,131] and photoinduced electron and energy transfer1132-1501 have been synthesized and studied. The fastest of these processes are intramolecular and intermolecular electron and energy transfer. This chapter details research in the development and applications of molecular switches based on these processes. 

The dependence of the dissociation constant kj) and the recombination constants kjt in the reaction (a) on the optical polarization of the atoms A was predicted by Bernheim [65] and Kastler [225] and later demonstrated experimentally [7, 363]. The dependence can be understood from the obvious fact that only hydrogen-like atoms with opposite electronic spins may recombine and form a molecule A2(X1E+). Hence we have kR = kft(l — S2), where S is the degree of electron spin polarization of the atoms. A convenient indicator of dimer formation is provided by the kinetics of the laser-induced molecular fluorescence after switching on magnetic resonance which destroys the polarization of the atoms, as performed by Huber and Weber [201] for a Na — Na2 mixture. The se-... 

Scheme 4.5 A pH-responsive molecular switch that signals by color and fluorescence changes.

Bergonzi R, Fabbrizzi L, Licchelli M, Mangano C. Molecular switches of fluorescence operating through metal centred redox couples. Coord Chem Rev 1998 170 31-47. 

The suitability of fluorescent PET systems for use in the emerging field of molecular switching devices was pointed out in Sect. 4 due to their natural on-off action induced by ion input. Discussions in Sect. 6 have also illustrated the value of PET sensor ideas in the design of reagents and also of reporters on receptor-guest interactions. Such versatility of the fluorescent PET sensor logic makes this research worthwhile. 

J. Foiling et ah. Fluorescence nanoscopy with optical sectioning by two-photon induced molecular switching using continuous-wave lasers. Chem. Phys. Chem. 9, 321-326 (2008)... 

Fig. 7. A Schematic representation of a multicomponent system consisting of linked input and output units. B A pH-input fluorescence-output molecular switch. C A two-component redox-input fluorescence-output molecular switch. D A four-component redox-input fluorescence-output molecular switch. The fluorescence spectra in B, C and D are adapted from [32], [33] and [34], respectively, with permission...

Fig. 9. Molecular switching of fluorescence as a function of ion binding A with H+ ion binding and B with Na+ or K+ ion binding...

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