Fluorescence study, hydrophobically

Harrsch, C., Leo, A. Hoekman, D. (1995) Exploring QSAR Hydrophobic, Electronic, and Steric Constants, Washington DC, American Chemical Society Herrrrrrirrki, K. (1979) Fluorescence study of DNA alkylation by epoxides. Chem.-biol. Interact, 28, 269-278... 

Fluorescence emission spectrum of Mb shows a peak located at 629 nm. The fluorescence lifetime is dominated by decay equal to 17.8 ns with fractional contribution equal to 98%. The peak of the first emission band is close to that of the emission occurring when protoporphyrin is dissolved in water. This could indicate that the heme pocket is polar, altliough X-ray diffraction studies (Fraunenfelder et al. 1979) and fluorescence studies using TNS as a probe (Lakowicz and Keating-Nakamoto, 1984) have indicated that heme pocket of myoglobin is hydrophobic. Anyway, this hydrophobic feature of the heme pocket is characteristic to all hemoproteins. Therefore, one may conclude that porphyrin cannot be an indicator of the polarity of the heme pocket. 

The third example concerns a series of our LS and fluorescence studies on the structure and dynamics of micellar shells formed by weak PEs [90, 91] and the effects caused by the hydrophobic modification of shell-forming blocks [92-96]. 

We addressed the above problem by studying a system of modified PS-PMA micelles with long PMA blocks end-tagged by a strongly hydrophobic molecule in mixtures of water with organic solvents and in purely aqueous media where electrostatic effects dominate the behavior [93-96]. We used anthracene (An) as the end-attached hydrophobic group, which allowed for fluorescence study. When we started the study, it was not a priori clear what would happen when such slightly modified micelles were dispersed in aqueous media. 

Fluorescence studies of volume phase transition of polyacrylamide (PAAM) in mixed acetone/ water solvent, with incorporated dansyl group and pyrenyl probe were reported by Hu and co-workers [70, 71]. They observed an increase in the fluorescence lifetime of the probe with increase of acetone content in the solvent. They reported that gradual increase of fluorescence lifetime accompanies the volume phase transition of the PAAM gels from the swollen to collapsed state with increasing hydrophobicity of the microenvironment. 

Interactions of Hydrophobically Modified Poly(A -Isopropylacrylamides) with Liposomes Fluorescence Studies... 

While hydrophobically modified nonionic polymers are encountered far less frequently than their ionic counterparts, one can find several fluorescence studies of their interaction with surfactants. These include investigations of the HM-HEC/SDS system by Dualeh and Steiner (100) and by Sivadasan and Somasundaran (117) of the same polymer with added SDS and also the nonionic surfactant CnEOg. A comprehensive study. 

Carboxylic acids, salts, and esters can also be prepared by treatment of anion 3 with CO2. (19) The 50% substituted salt 6 (where x = y) is the first water soluble derivative of a poly(alkyl/arylphos-phazene). The salts are readily converted to the corresponding carboxylic acids upon protonation or to esters when treated with an activated species such as 4-N02CgH5CH2Br. Fluorescence studies of these simple acids indicate that they form a moderately hydrophobic environment in aqueous media. (20)... 

Hydrophobic associations in random copolymers of AMPS and iV-d ecylmethacrylamide (DodMAm) were investigated by viscometry, QELS, capillary electrophoresis (CE), NMR relaxation, and various fluorescence techniques (24,48), For fluorescence studies, the polymers that are singly-labeled with pyrene or naphthalene or doubly-labeled with pyrene and naphthalene (Chart 2) were employed (48). In this section, the self-association behavior of AMPS-DodMAm co lymers in water will be discussed with a focus on intra- and interpolymer self-associations as a function of the DodMAm content (/bod) in Ae copolymer. 

This chapter describes the most important fluorescence studies of the behavior of polymer chains in solutions, gels, and melts and in the bulk amorphous state. Because the book contains several chapters devoted to specific systems and methods, we try to avoid duphcities concerning, e.g., self-assembled core-shell nanoparticles, the behavior of hydrophobically modified chains, and PCS studies of polymers in solutions, and turn our attention to other aspects. Nevertheless, it was sometimes necessary to mention some topics treated in the other chapters. 

The excimer fluorescence studies of hydrophobically modified polymers, developed by Winnik, Yekta, Duhamel, and others, which have been widely used also by other groups for solution of various problems, are treated in a chapter Pyrene-Labeled Water-Soluble Macromolecules as Huorescent Mimics of Associative Thickeners. ... 

Since synthetic copolymers seldom exhibit intrinsic fluorescence, either covalently bound fluorescent labels or non-covalently bound fluorescent probes are necessary for the vast majority of fluorescence studies of block copolymer micelles. The former are mostly attached during the synthesis of the copolymer [18]. This could be done conveniently by using a fluorescent initiator and/or fluorescent terminating agent. In such cases, the labels are located at the ends of the blocks or in between of them. Fluorescent probes can be used for studies of amphiphilic block copolymer micelles in aqueous solutions where strong hydrophobic effect allows for binding of the probe either in the micellar core (hydrophobic probes) [19] or in the iruier part of the shell close to the core/shell interface (amphiphilic probes) [20]. The latter, developed mainly for membrane studies, are derivatives of... 

Ringsdorf H, Venzmer J, Winnik FM (1991) Fluorescence studies of hydrophobically modified poly(Af-isopropylacrylamide) or how to play accordion on a liposome. Makromol Chem Macromol Symp 46 427-431... 

Hu Y-Z, Zhao C-L, Winnik MA, Sundararajan PR (1990) Fluorescence studies of the interaction of sodium dodecyl sulfate with hydrophobically modified poly(ethylene oxide). Langmuir 6 880-883... 

More recently, the problem has been attacked by Chance and his associates using the fluorescent probes successfully employed in the study of the conformational changes of proteins. These dyes do not fluoresce in water, but become fluorescent in hydrophobic environments. They can be bound to mitochondria, or to... 

Comparative fluorescence studies by Harris show that while there is no measurable difference in the mobility of a fluorescent probe in the interior of ethanol-treated membranes of the LS and SS mice, there is a difference in the mobility of a surface probe, with the greater mobility at the surface of the LS mice membranes . While the strains show a difference in their sensitivity to ethanol, they show the same sensitivity to the more hydrophobic alcohol butanol, even though both alcohols elicit the same disordering effects at the interior of the bilayer, albeit at different concentrations. ... 

---