Eosin structure

Quantitative analysis of the results obtained has shown that a single eosin guest is sufficient to completely quench the fluorescence of any excited dansyl unit of the hosting dendrimer. Fluorescence lifetime measurements indicated that the dye molecules can occupy two different sites (or two families of substantially different sites) in the interior of the dendritic structure. 

Fig. 6 General structure of xanthene dyes containing fluorescein, eosin, and rhodamine...

Other zinc solutions, free of formaldehyde, have been proposed.29 31 All of these simple buffered salt solutions preserve immunoreactivity well and are suitable for DNA, RNA, and proteomics research. Judging by published photomicrographs of hematoxylin and eosin-stained specimens, cytological detail is inferior to that achieved with standard formalin. Nuclei are condensed to the point where many lack chromatin patterns.3132 Such zinc salt solutions may be good for specialized purposes but are best used as special fixatives. To get good structural detail as well, specimens should be split so that a portion can... 

To obtain tissue preparations whose constituents were maintained as closely as possible to their state in vivo, the material had to be fixed, i.e. the enzymes inactivated so that cell structures were instantaneously preserved, an almost unattainable ideal. Formalin was the favored fixative, but others (e.g. picric acid), were also employed. Different methods of fixation caused sections to have different appearances. Further artifacts were introduced because of the need to dehydrate the preparations so that they could be stained by dyes, many of which were lipid-soluble organic molecules. Paraffin wax was used to impregnate the fixed, dehydrated material. The block of tissue was then sectioned, originally by hand with a cut-throat razor, and later by a mechanical microtome. The sections were stained and mounted in balsam for examination. Hematoxylin (basophilic) and eosin (acidophilic) (H and E staining) were the commonest stains, giving blue nuclei and pink cytoplasm. Eosinophils in the blood were recognized in this way. 

Figure 14.2. Chemical structures of some commonly used organic fluorescent probes 1, fluorescein-5-isothiocyanate (FITC) 2, tetramethylrhodamine-5-isothiocyanate (TRITC) 3, 5-carboxyrhodamine B 4, rhodamine X isothiocyanate (XRITC) 5, malachite green isothiocyanate 6, eosin-5-isothiocyanate 7, 1-pyreneisothiocyanate 8, 7-dimethylaminocoumarin-4-acetic acid 9, CY5.180Su.

Fig. 25.2 Survival of a split-thickness skin graft applied over Permacol paste. SSG day 0, assessed 6 days post grafting, haematoxylin and eosin, xlOO. Epithelium of a split-thickness skin graft (SSG) was viable and well-structured. Dermal component of the graft was intimately attached to the well-cellularised Permacol paste PP) with minimal signs of the inflammatory reaction. Dermal substitute biomaterial integrated into the full-thickness wound via granulation tissue in growth present at the paste and wound bed (WB) interface...

Eosin Y stands for Eosin Yellowish and it is the disodium salt of tetrabromofluorescein. There are a number of other fluorescein derivatives which are also referred to as Eosins. Eosin B or bluish is 4,5-dibromo-3,7-dinitrofluorescein. The investigator is best advised to buy dyes on the basis of structure rather than name. In the case of the other dyes in the table the literature confusion is less imposing. 

We have also used the Eosin-triethanolamine system to design a two-photon system based on visible laser-induced photopolymerization followed by UV-induced crosslinking as a means of building a three-dimensional network structure aimed at three-dimensional imaging. The key to our design, shown in Scheme 4 below, is incorporation of an acrylate monomer... 

The hole formation in the liposomal membrane after treating the vesicles with reducing agents can be demonstrated by the fast and complete release of eosin, a fluorescent marker. Final proof that the polymeric backbone of the uncorked vesicles does not collapse comes from scanning electron microscopy. Fig. 56 shows the spherical structure of the liposomes with holes. 

Certain fluorescent compounds, such as formycin nucleotides and eosin, behave as noncovalently binding ATP analogs, and their fluorescence increases upon association with the ATPases. The transition from the Na+-form to the K+-form of Na+-K+-ATPase gives rise to a decrease in fluorescence from these probes. The fluorescence of fluorescein isothiocyanate (FITC) bound covalently at the nucleotide site of Na+-K+-ATPase (Table 3) also decreases in relation to transition from the Na+-form to the K+-form. With the noncovalent as well as with the covalently-binding probes the fluorescence decrease probably reflects the structural change in the nucleotide site associated with the reduced nucleotide affinity in the E2 form (see above). By contrast, when FITC is attached to the SR Ca2+-ATPase (at the residue homologous to the FITC-binding residue in Na+-K+-ATPase) the fluorescence increases upon removal of Ca2+. Most likely this relates to the above discussed difference between Na+-K+-ATPase and Ca2+-ATPase with respect to the existence of a stable E2 form with low affinity for nucleotide. 

Poly(propyleneamine) dendrimers of generations 1 and 4 (89) functionalized with azobenzene groups were investigated as hosts for eosin Y (eosin = 2, 4, 5, 7 -tetrabromofluorescein dianion) in DMF solution [159]. The peripheral azobenzene groups can be switched by light excitation from the E to the Z form. The fluorescent excited state of eosin is reductively quenehed by the tertiary amine units present in the dendrimer structure. This electron transfer quenching takes place with a static... 

The formation of donor-acceptor complexes between bipyridinium salts (electron acceptors) and xanthene dyes (electron donors) (e.g., eosin. Rose Bengal) has been studied extensively. Crystal structures of these complexes have been identified, and the structural features of the donor-acceptor complexes in solutions have been characterized using NMR spectroscopy. The xanthene dye/bipyridinium donor-acceptor complexes are stabilized by... 

Wilber, I., Eichen, Y., Rabinovitz, M., Hoffman, R., and Cohen, S. Structure and thermodynamic and kinetic properties of eosin biptridinium complexes. J. Am. Chem. Snc. 1992, 114,637-644. 

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