Photochromic labels method

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. 

Likhtenshtein, G.I. Khudjakov, D.V., and Fogel, V.R. (1992) Photochrome-labeling methods in study of dynamics ofbiological systems, J. Biochim. Biophys Methods, 25, 219-229. 

Likhtenshtein, G. I. Khudjakov, D. V. Vogel, V. R. Photochrome-labeling method in study of dynamics... 

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). 

Papper, V., Medvedeva, N., Fishov, I., and Likhtenshtein, G.I. (2000) Quenching of cascade reaction between triplet and photochrome probes with nitroxide radicals novel labeling method in study ofmembranes and surface system, 7. Appl. Biotech. Biophys. 88, 1-17. 

A number of techniques have been employed to examine free volume properties of polymers. These include small angle x-ray scattering and neutron diffraction that have been used to determine denisty fluctuations to deduce free volume size distributions [4-7]. Photochromic labelling techniques by site specific probes have been developed to monitor the rate of photoisomerizations of the probes and from this deduce free volume distributions [8-11]. Additional probing methods used to probe voids and defects in materials such as scanning tunneling microscopy (STM) and... 

During the past decade, theoretical calculations of hyperpolarizabilities have been performed to help synthetic chemists design optimum NLO structures. Although extremely accurate calculations are still out of reach, it is now possible to predict the influence of structural changes on the NLO coefficients. In the case of photochromes, theoretical calculations may be useful for predicting 3 values of thermally unstable colored forms. The theoretical methods generally employed to calculate molecular hyperpolarizabilities are of two types those in which the electric field is explicitly included in the Haniiltonian, frequently labeled as Finite Field (FF) and those which use standard time dependent perturbation theory, labeled Sum Over State (SOS) method. 

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

A fiuorescent-photochrome method of quantifying the orientation of solid-phase antibodies immobilized on a silica plate was proposed [9]. The method is based on the measurement of fiuorescence quenching by a quencher in solution, rates of trans-cis photoisomerization and photodestruction of a stilbene-labeled hapten in an antibody binding site. These experimental parameters enable a quantitative description of the order of binding sites of antibodies immobilized on a surface and can be used to characterize the micro viscosity and steric hindrance in the vicinity of the binding site. Furthermore, a theoretical method for the determination of the depth of immersion of the fiuorescent label in a two-phase system was developed [9]. 

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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