Charge-shift probes

Fluhler E, Burnham VG, Loew LM (1985) Spectra, membrane-binding, and potentiometric responses of new charge shift probes. Biochemistry 24(21) 5749-5755... 

Table I. Spectroscopic and Binding Properties of Charge-Shift Probes...

Loew, L.M., Cohen, L.B., Salzberg, B.M., Obaid, A.L., Bezanilla, F. Charge-shift probes of membrane potential. Characterization of aminostyrylpyridinium dyes on the squid giant axon. Biophys. J. 47, 71-77 (1985)... 

Hassner, A. Bimbaum, D. Loew, L. M. Charge-shift probes of membrane potential synthesis. J. Org. Chem. 1984, 49, 2546-2551. 

Loew LM, Bonneville GW, Surow J (1978) Charge shift optical probes of membrane-potential - theory. Biochemistry 17(19) 4f)65—4071... 

Loew LM, Scully S, Simpson L, Waggoner AS (1979) Evidence for a charge-shift electro-chromic mechanism in a probe of membrane-potential. Nature 281(5731 ) 497—499... 

Figure 3.38. Change of bond order upon charge shift for the probe 53.

Molecular dynamics simulations focused on the solvation dynamics of a hypothetical dimer probe molecule in [C2mim][PF6] and [C2mim][Cl] have been done by Kim and co-workers.The solvation dynamics were characterized by the time correlation function of the vertical energy difference of two solute states relevant to a charge shift. The vertical energy difference between an initial state i and a final state /, AEj f, is assumed to be comprised of only Coulombic terms. The time correlation function is computed as... 

Compared to oxo-squaraines or other ring-substituted squaraines, amino-squaraines 39 [45, 52, 112] have ionic character, similar to open-chain cyanine dyes, and due to the positive net charge, these dyes are to some extend water-soluble. Amino-squaraines absorb and emit at longer wavelength than the corresponding oxo-squaraines the absorption maxima are between 650-710 nm (eM = 85,000-300,000 M-1cm-1) [45, 112], The increase in solvent polarity is accompanied by a hypsochromic shift of the absorption. Amino-squaraine dyes are potentially used as fluorescent probes but because their photostability is inferior to those of oxo-squaraines and other ring substituted squaraines of similar structure, their applications are rather limited. 

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