Photoswitchable molecular probes

Liquid Membrane Ion-Selective Electrodes Response Mechanisms Studied by Optical Second Harmonic Generation and Photoswitchable lonophores as a Molecular Probe... 

IV. MOLECULAR PROBE FOR ISE MEMBRANE POTENTIALS BASED ON PHOTOSWITCHABLE AZOBIS(BENZO-15-CROWN-5) lONOPHORES [17]... 

If the photoequilibrium concentrations of the cis and trans isomers of the photoswitchable ionophore in the membrane bulk and their complexation stability constants for primary cations are known, the photoinduced change in the concentration of the complex cation in the membrane bulk can be estimated. If the same amount of change is assumed to occur for the concentration of the complex cation at the very surface of the membrane, the photoinduced change in the phase boundary potential may be correlated quantitatively to the amount of the primary cation permeated to or released from the membrane side of the interface under otherwise identical conditions. In such a manner, this type of photoswitchable ionophore may serve as a molecular probe to quantitatively correlate between the photoinduced changes in the phase boundary potential and the number of the primary cations permselectively extracted into the membrane side of the interface. Highly lipophilic derivatives of azobis(benzo-15-crown-5), 1 and 2, as well as reference compound 3 were used for this purpose (see Fig. 9 for the structures) [43]. Compared to azobenzene-modified crown ethers reported earlier [39 2], more distinct structural difference between the cis... 

It is at present still difficult to correlate the absolute intensity of the SHG with the number of cationic complexes at the membrane surface. Therefore, a quantitative discussion, showing how the permselective uptake of primary cations forming SHG active complexes into the membrane side of the phase boundary corresponds to the increase in the membrane potential, is not possible yet. Lipophilic derivatives of photoswitchable azobis(benzo-15-crown-5) were recently shown as a molecular probe to determine photoinduced changes in the amount of the primary cation uptake into the membrane phase boundary in relation to the photoinduced EMF changes under otherwise identical conditions. 

Tohda, K. Yoshiyagawa, S. Kataoka. M. Odashima. K. Umezawa, Y. Photoswitchable azobis(benzo-15-crown-5) derivatives as a molecular probe for phase boundary potentials at ion-selective poly (vinyl chloride) liquid membranes. Anal. Chem. 1997. 69, 3360-3369. 

Umezawa, Y. Liquid Membrane Ion-Selective Electrodes Response Mechanisms Studied by Optical Second Harmonic Generation and Photoswitchable lonophores as a Molecular Probe. In Liquid Interfaces in Chemical, Biological, and Pharmaceutical Applications Volkov. A.G.. Ed. Marcel Dekker, Inc. New York, 2000 439-468. 

Science is entering into the nanoscale world, and the organization of microscale or nanoscale biomaterial structures on surfaces has been demonstrated and is a subject of extensive research effort.184,851 Single biomaterial molecules have been imaged on surfaces,186 871 and the individual affinity interactions of biomaterials probed at the molecular level.188,891 While the different scanning microscopy techniques provide useful means to image and manipulate biomaterials on surfaces, the use of the near-field scanning optical microscope (NSOM) 9<) in the activation of photoswitchable biomaterials on surfaces should be emphasized specifically. One... 

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