Fluorescence-photochrome method

Theoretical considerations and existing experimental data indicate that under certain conditions, the rate of photoisomerization strongly depends on the microviscosity around the isomerized molecule and upon the effect of steric hindrance. In a viscous medium, the apparent rate constant of trans-cis photoisomerization ki o is controlled by the reorganization rate of the process in the medium (Equations 4.2 and 4.3). This method was used for the measurement of fluidity of biological membranes and microviscosity of a specific site of a protein. On this theoretical basis, fluorescence-photochrome immunoassay (FPHIA)] were used. 

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As seen in Figure 10.7, the fluorescence-photochrome method allows to measure the probe motion as a whole in temporal scale dose to the fluorescence lifetime and in the same time and the same space to detect twisting of stilbene fragment in the singlet excited states for 180° in the microsecond scale. A separation of effects of a probe rotation frequency and angle of twisting appears to be a serious problem in fluorescence and spin probing. 

Thus, the fluorescence-photochrome method may, in certain conditions, gain advantage over conventional fluorescence, and spin labeling is simpler, more sensitive, and informative. 

A Fluorescent-Photochrome Method for the Quantitative Characterization of Solid-Phase Antibody Orientation... 

The fluorescence—photochrome method is also suitable for characterizing the physical parameters of a wide range of immobilized systems, such as proteins, enzymes, lipids, and polymer films. 

In 09NJC1320, an original method was developed for the preparation of fluorescent photochrome 112, which contains both electron-donating and electron-withdrawing groups and bipyridine-bridged dithienylethene fragments, from 110 with bisphosphonate bipyridine 111 in the presence of a base (Scheme 36). 

The triplet-photochrome method is based on the above mentioned cascade scheme. Starting from ctT-stilbene, which is not fluorescent at the steady-state conditions of our... 

A new photochrome-fluorescence-spin method for the simultaneous quantitative analysis of the redox status and viscosity of a medium has been developed [20], The method of the viscosity measurement is based on the use of double fluorescence-nitroxide molecules. 

The triplet-photochrome method is based on the above-mentioned scheme. Starting from cis-stilbene, which is not fluorescent at the steady-state conditions, and measuring the rate of increase of emitted fluorescence, it has been possible to monitor the process of the sensitized cis-trans photoisomerization. The cis-stilbene concentration, which is proportional to fluorescence intensity, approaches the photo stationary level exponentially with the rate constant... 

The traditional fluorescence and electron-spin resonance methods for recording molecular collisions do not allow the study of translational diffusion and rare encounters of molecules in a viscous media because of the short characteristic times of these methods. To measure the rate constants of rare encounters between macromolecules and to investigate the translation diffusion of labelled proteins and probes in a medium of high viscosity (like biomembranes), a new triplet-photochrome labeling technique has been developed (Mekler and Likhtenshtein, 1986 Mekler and Umarova, 1988 Likhtenshtein, 1993 Papper and Likhtenshtein, 2001). 

The triplet-photochrome labeling method has been used to study very rare encounters in a system containing the Erythrosin B sensitiser and SITC photochrome probe (Mekler and Likhtenshtein, 1986). Both types of the molecules were covalently bound to a-chymotrypsin. The photoisomerisation kinetics was monitored by fluorescence decay of the frans-SITS. The rate constants of the triplet-triplet energy transfer between Erythrosin B and SITS (at room temperature and pH 7) were found k,r = 2 xlO7 NT s-1 and ktT = 107 M V. It should be emphasized that the concentration of the triplet sensitiser attached to the protein did not exceed 10 7 M in those experiments, and the collision frequencies were close to 10 s 1 which are 8-9 orders of magnitude less than those measured with the regular luminescence or ESR techniques. 

Parkhomyuk-Ben Arye, P., Strashnikova, N. V., Iikhtenshtein G. I. (2001) Stilbene photochrome-fluorescence-spin molecules covalent immobilization on silica plate and applications as redox and viscosity probes, J. Biochem. Biophys. Methods (in press)... 

Oxidation of tetramethylorthothiophenophanes with m-CPBA gave a mixture of thiophene 1,1-dioxides 55 and 56 in a ratio depending on the amount of m-CPBA used (Scheme 55) [65], The thiophene 1,1-dioxide 57 could also be easily obtained using this oxidant (Scheme 56) [66], Application of this method produced novel photochromic compounds 58-60, having relatively high fluorescence efficiencies (Scheme 57) [67], as well as the precursors 61-63 for electron-transporting materials (Scheme 58) [68],... 

Trends in Photochem. Photobiol. 1994 3 243-260 Fujii T., Mishima S., Kawauchi O. Effects of Si-Al composition on the fluorescence spectra of 1-naphthol during the sol-gel-xerogel transitions. Res. Chem. Intermed. 1997 23 143-154 Fujii T., Kodaira K., Kawauchi O., Tanaka N., Yamashita H., Anpo M. Photochromic behavior in the fluorescence spectra of 9-anthrol encapsulated in Si-Al glasses prepared by the sol-gel method. J. Phys. Chem. B 1997 101 10631-10637... 

Photochromic behavior in the fluorescence spectra of 9-anthrol encapsulated in Si-Al glasses prepared by the sol-gel method. /, Phys. Chem. B,... 

ABSTRACT. Over the past 15 years, a number of transient optical grating techniques have been developed for measurements of the transport properties of materials. Such methods have been used to measure the tracer diffusion coefficients of polymer molecules which have been labeled with photochromic or fluorescent dyes. The present paper describes the common features of these techniques, and gives an example of how Fluorescence Redistribution After Pattern Photobleaching has been used to study the diffusion of polymer molecules in the melt. 

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