Hydrophobic chromophore

We will be concerned in Chapter 6 with photoinduced ET of hydrophobic chromophores that are confined to the microphase structure of amphiphilic polyeletrolytes. 

More recently, several groups have investigated electrostatic effects on the fluorescence quenching of hydrophobic chromophores covalently attached to various polyanions. The photophysics of the chromophores incorporated in the polyeletrolytes at small mole fractions is relatively simple, because no interaction is expected to occur between the incorporated chromophores. For this reason, most of the studies have focused on amphiphilic polyeletrolytes loaded with a low amount of hydrophobic chromophores. 

More recently, Webber et al. [125, 126] have extensively studied photoinduced ET for various hydrophobic chromophores covalently bound to PMA by using... 

In Edman sequencing, the N-terminal amino acids are sequentially cleaved and labeled with a hydrophobic chromophore. Then, the labeled... 

The NMR structures of PYP lacking the N-terminal 25 residues were reported under the dark and illuminated conditions [34]. In the NMR structure of the M intermediate, the three regions at residues 42-58, 63-78, and 96-103 (the amino-acid positions in intact PYP) are highly disordered to bring the exposure of the hydrophobic chromophore to the solvent. Although the structural changes in the a4 helix (residues 55-58) and the loop connecting... 

Is Inversely proportional to solvent viscosity In non-protonic solvents, as expected for a diffusion-controlled process. (14) However, In water and methanol the extent of exclmer emission and the rate of Intramolecular exclmer formation were substantially greater than one would Infer on the basis of solvent viscosity alone. They suggested that the hydrophobic chromophore Is undoubtedly better solvated by the environment within the polymer coll than If the pyrene were surrounded completely by water or methanol. This situation would be expected to lead to an Increased due to a reduced distance of separation between pyrenes. 

The chromophore-stabilizing mechanism of neocarzinostatin had been discussed mainly based on a hydrophobic interaction of the highly hydrophobic chromophore molecule in its binding site.62 On the basis of the new findings of the solution structure, a new mechanism in addition to the hydrophobic... 

Recently, spiropyran-initiated hyperbranched polyglycerol (SP-hb-PG) micelles were reported [70]. These carriers responded to UV/visible light and could dissociate due to conversion of the hydrophobic chromophore SP to zwitterionic and hydrophilic merocyanine (ME). In addition, chromophores such as coumarin, o-nitrobenzyl, stilbene, dithienylethene and 2-diazo-l,2-napthoquinone (DNQ) have been employed in light-responsive micelles, which can respond either to UV/ visible or NIR irradiation to undergo structural or phase changes and trigger the drug release from micelles [71-74]. 

PouLTER, L. Burlingame, A. L. Desorption mass spectrometry of oligosaccharides coupled with hydrophobic chromophores. Methods Enzymol. 1990, 193, 661-689. 

Phthalocyanine Dyes. The phthalocyanine molecule is much too big to be used on hydrophobic fibers and therefore is only used in its sulfonated form as the basis for direct and reactive dyes (see Phthalocyanine compounds). Its forces of attraction are different from a small linear yeUow a2o dye with which it is used to form bright greens. CompatibiHty between the two is likely to be a problem in practice and to overcome this, green dyestuffs containing a phthalocyanine dye linked via a saturated chromophore blocker (—x—) have been made, eg,... 

Humic materials fractionated on the basis of hydrophobicity and proton affinity continue to exhibit two fluorophores as discussed in the section "Exciation-Emission Spectra. Strong evidence to establish the existence of at least two chromophores is seen in the phase-resolved spectra. These spectra are shown in Figures 4 a-f. They consist of the phase-resolved emission spectrum of each of the two fluorophores plotted separately and the normal emission spectrum of the humic fraction. If the nulling out of one fluorophore is exact then the sum of the two separate phase resolved spectra should be additive to equal the normal spectrum. In these figures the normal emission spectrum was measured separately from the two phase resolved emision spectra. The phase resolved spectra were then superimposed onto the scan of the normal emission spectrum. 

Water-soluble polymeric dyes have been prepared from water-insoluble chromophores, viz., anthraquinone derivatives. Unreacted chromophore and its simple derivatives, which are all water-insoluble, remain in solution due to solubilization by the polymeric dye. A method has been developed to separate and quantitate the polymeric dye and these hydrophobic impurities using Sephadex column packing. The solvent developed has the property of debinding the impiirities from the polymer, and further allows a separation of the imp irities into discrete species. This latter separation is based on the functional groups on the impurity molecules, having a different interaction with the Sephadex surface in the presence of this solvent. The polymer elutes at the void volume... 

Owing to their chemical structure, carotenes as polyterpenoids are hydrophobic in nature (Britton et al., 2004). Therefore, as it might be expected, the carotenes are bound within the hydrophobic core of the lipid membranes. Polar carotenoids, with the molecules terminated on one or two sides with the oxygen-bearing substitutes, also bind to the lipid bilayer in such a way that the chromophore, constituted by the polyene backbone is embedded in the hydrophobic core of the membrane. There are several lines of evidence for such a localization of carotenoids with respect to the lipid bilayers. 

Fluorescence probes possessing the PyU base 46 selectively emit fluorescence only when the complementary base is adenine. In this case, the chromophore of is extruded to the outside of the duplex because of Watson-Crick base pair formation, and exposed to a highly polar aqueous phase. On the contrary, the duplex containing a PyU/N (N = G, C and T) mismatched base pair shows a structure in which the glycosyl bond of uridine is rotated to the syn conformation. In this conformation, the fluorophore is located at a hydrophobic site of the duplex. The control of base-specific fluorescence emission is based on the polarity change in the microenvironment where the fluorophore locates are dependent on the l>yU/A base-pair formation. 

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