Caged fluorescein

Fig. 2. Uniform stimulus and switching time, (a) A solution of 10 pM DMNB-caged fluorescein is transported by the flow from /effto right. Photochemical release of the dye is initiated inside the white rectangle by rapid scanning of a 405-nm laser, (b) The fluorescence intensity is measured in a small rectangular region around the position of the cell in (a). The average intensity is shown in the course of time. Less than 1 s is required for switching of the dye concentration at the location of the cell. Reproduced with permission from ref.f Copyright 2007 American Chemical Society.

For calibration, an identical photo-uncaging experiment is performed with a 10-pM solution of 4,5-dimethoxy-2-nitrobenzyl (DMNB)-caged fluorescein (dextran conjugate,... 

Fig. 13. The distribution of the symplasmic tracer (CMNB - caged fluorescein (fluorescein bis-(5-carboxymethoxy-2-nitrobenzyl ether, dipotassium salt) within the Ambidopsis somatic embryo, showing a border in symplasmic communication between the root meristem and other parts of the somatic embryo, which indicates that the symplasmic subdomains correspond with the main morphological parts of the embryo (fluorescence microscope h - hypocotyl, c - cotyledon, r - root bar = 150 pm author - Wrobel, PhD thesis).

The dynamics of proton binding to the extra cellular and the cytoplasmic surfaces of the purple membranes were measured by the pH jump methods [125], The purple membranes selectively labeled by fluorescein Lys-129 of bacteri-orhodopsin were pulsed by protons released in the aqueous bulk from excited pyranine and the reaction of the protons with the indicators was measured. Kinetic analysis of the data implied that the two faces of the membrane differ in then-buffer capacities and in their rates of interaction with bulk protons. The extracellular surfaces of the purple membrane contains one anionic proton binding site per protein molecule with pA" 5.1. This site is within a Coulomb cage radius from Lys-129. The cytoplasmic surface of the purple membrane bears four to five pro-tonable moieties that, due to close proximity, function as a common proton binding site. The reaction of the proton with this cluster is at a very fast rate (3 X 1010 M-1 sec ). The proximity between the elements is sufficiently high that even in 100 mM NaCl, they still function as a cluster. Extraction of the chromophore retinal from the protein has a marked effect on the carboxylates of the cytoplasmic surface, and two to three of them assume positions that almost bar their reaction with bulk protons. Quantitative evaluation of the dynamics of proton transfer from photoactivated bacteriorhodopsin to the bulk has been done by using numerical... 

In composite plastic microchannels, there is an additional problem of extra dispersion (Taylor dispersion) in EOF which is caused by the difference in zeta potentials of the different materials forming the channels [258]. Caged fluorescent dye (fluorescein bis[5-carboxymethyoxy-2-nitrobenzyl]ether dipotassium salt) was used to visualize the greater dispersion obtained in acrylic or composite channels due to non-uniformity in the surface charge density [259]. 

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