Fluorophores pyrene

FRET has been used in [66] to probe dynamic behavior of the hexaresorcinarene ligands 402 and 403, and their cage complexes. The resor-cinarenes 183 and 184 with donor and acceptor fluorophore pyrene- and perylene-containing... 

In two other studies, it was observed that C60 in LB films can quench the fluorescence of pyrene [293] and of 16-(9-anthroyloxy)palmitic acid [294] by photoinduced electron transfer. In these studies, both C60 and the electron-donating fluorophore were incorporated into a tricosanoic acid LB film in different ratios. 

Pyrene fluorophores are also used as probes. Derivatives of pyrene show /.max/ Xem 340/376 nm, e 4.3 x 104 M 1 cm-1, and environmental sensitivity, this fluorophore can be used to report on RNA folding [102]. Pyrene also displays a long-lived excited state (x > 100 ns), which allows for an excited pyrene molecule to associate with a pyrene in the ground state. The resulting eximer exhibits a red-shift in fluorescence intensity (A,em 490 nm). This characteristic can be used to study important biomolecular processes, such as protein conformation [103]. 

Masuko M, Ohtani H, Ebatal K, Shimadzu A (1998) Optimization of excimer-forming two-probe nucleic acid hybridization method with pyrene as a fluorophore. Nucleic Acids Res 26 5409-5416... 

Kool and co-workers recently reported a multicolor set of water-soluble dyes synthesized through the combination of three to five individual fluorophores assembled on a DNA-like backbone [94, 95]. As a continuation of their previous works on various DNA analogs [96-99], they synthesized the oligodeoxyfluoro-side (ODF) with seven fluorescent monomers, such as pyrene, perylene, dimethy-laminostilbene, and three stilbene derivatives, and they assembled these fluorescent DNA monomers into oligofluor chains using a DNA synthesizer (Fig. 26). Using... 

Cascade Blue cadaverine and Cascade Blue ethylenediamine both contain a carboxamide-linked diamine spacer off the 8-methoxy group of the pyrene trisulfonic acid backbone. The cadaverine version contains a 5-carbon spacer, while the ethylenediamine compound has only a 2-carbon arm. Both can be coupled to carboxylic acid-containing molecules using a carbodiimide reaction (Chapter 3, Section 1). Since Cascade Blue derivatives are water-soluble, the carbodiimide EDC can be used to couple these fluorophores to proteins and other carboxylate-containing molecules in aqueous solutions at a pH range of 4.5-7.5. The reaction forms amide bond linkages (Figure 9.39). 

A first generation poly(amido amine) dendrimer has been functionalized with three calyx[4]arenes, each carrying a pyrene fluorophore (4) [30]. In acetonitrile solution the emission spectrum shows both the monomer and the excimer emission band, typical of the pyrene chromophore. Upon addition of Al3+ as perchlorate salt, a decrease in the excimer emission and a consequent revival of the monomer emission is observed. This can be interpreted as a change in the dendrimer structure and flexibility upon metal ion complexation that inhibits close proximity of pyrenyl units, thus decreasing the excimer formation probability. 1H NMR studies of dendrimer 4 revealed marked differences upon Al3+ addition only in the chemical shifts of the CH2 protons linked to the central amine group, demonstrating that the metal ion is coordinated by the dendrimer core. MALDI-TOF experiments gave evidence of a 1 1 complex. Similar results have been obtained for In3+, while other cations such as Ag+, Cd2+, and Zn2+ do not affect the luminescence properties of... 

The width of a band in the absorption or emission spectrum of a fluorophore located in a particular microenvironment is a result of two effects homogeneous and inhomogeneous broadening. Homogeneous broadening is due to the existence of a continuous set of vibrational sublevels in each electronic state. Absorption and emission spectra of moderately large and rigid fluorophores in solution could therefore be almost structureless at room temperature. However, in some cases, many of the vibrational modes are not active, neither in absorption nor in emission, so that a dear vibrational structure is observed (e.g. naphthalene, pyrene). 

E-3 (Figure 10.26) is the first example of an ionophoric calixarene with appended fluorophores, demonstrating the interest in this new class of fluorescent sensors. The lower rim contains two pyrene units that can form excimers in the absence of cation. Addition of alkali metal ions affects the monomer versus excimer emission. According to the same principle, E-4 was designed for the recognition of Na+ the Na+/K+ selectivity, as measured by the ratio of stability constants of the complexes, was indeed found to be 154, while the affinity for Li+ was too low to be determined. 

The Na+ sensor M-9 has a structure analogous to that of compound E-4, but instead of two identical pyrene fluorophores, it contains two different fluorophores with a pyrene group and an anthroyloxy group. Resonance energy transfer (see Chapter 9) from the former to the latter is then possible because of the spectral overlap between the fluorescence spectrum of the pyrene moiety and the absorption spectrum of the anthroyloxy moiety. Upon addition of Na+ to a solution of M-9 in a mixture of MeOH and THF (15 1 v/v), the fluorescence of the anthroyloxy group increases significantly compared with that of the pyrene group, which permits a ratiometric measurement. 

In compound 28,(59) the conformational change induced by sodium binding reduces the probability of collision between the pyrene fluorophore and the nitrobenzene quencher, both attached to the calixarene ring. 

In multicomponent systems A"0 can be written as a sum of the individual absorption coefficients A ot = 2TA , where each AT,(A ) depends in a different way on the wavelength. If one or more of the components are fluorescent, their excitation spectra are mutually attenuated by absorption filters of the other compounds. This effect is included in Eqs. (8.27) and (8.28) so that examples like that of Figure 8.4 can be quantified. The two fluorescent components are monomeric an aggregated pyrene, Mi and Mn. The fluorescence spectra of these species are clearly different from each other but the absorption spectra overlap strongly. Thus the excitation spectrum of the minority component M is totally distorted by the Mi filter (absorption maxima of Mi appear as a minima in the excitation spectrum ofM see Figure 8.4, top). In transparent samples this effect can be reduced by dilution. However, this method is not very efficient in scattering media as can be seen by solving Eqs. (8.27 and 8.28) for bSd — 0. Only the limit d 0 will produce the desired relation where fluorescence intensity and absorption coefficient of the fluorophore are linearly proportional to each other in a multicomponent system. 

Relatively few probes have been widely applied to FlAs. Fluorescein and rho-damine, their derivatives, and to some extent phycoerythrin have dominated immunoassays that are based on steady-state measurements. Dansyl, umbelliferone, coumarins, and pyrenes are among others that have been used. Several more commonly used dyes are shown in Figure 14.2. Shorter-wavelength dyes tend to be less useful since they excite at wavelengths where endogenous chromophores, fluorophores, and... 

Although many hydrocarbons exhibit fluorescence, often they are colourless and the fluorescence is only just into the blue, e.g. the linear terphenyl and quaterphenyl. Polycyclic ring systems such as terrylene and rubicene are used in analytical methods and OLEDs but a large number are ruled out of commercial use because of their potential to act as carcinogens. However, as mentioned in section 3.5.1.3, pery-lene is a useful fluorophore in a variety of outlets and pyrene is another polycyclic compound of interest. One derivative of pyrene (3.27) is a yellow-green fluorescent dye used in textile applications (Cl Solvent Green 7) and in analysis and sensors (see section 3.5.6.4). 

Pyrene shown a number of photophysical features that made it an attractive fluorophore to probe the microenvironment in micellar aggregates [19]. For the peaks of pyrene PL, two important peaks at about 373 nm and 390 nm among the five dominant peaks of pyrene fluorescence were numbered as 1 and III, respectively [20]. It has been known that intensity ratio of peak 111 to I (III/I) increased as the polarity at the solubilization site of pyrene decreases. Figure 6 shows fluorescence spectra (A.ex = 310 nm) of pyrene in precursor gel containing TPA and I-IV samples denoted as (a), (b), (c), (d) and (e), respectively. The value of 111/1 of pyrene does not change under silicalite-1 gel due to no formation of micelle. However, in the Fig. 6d (sample II), III/I ratio is rapidly increased, while sample III and IV are decreased slightly again. Previously, Park et al. have reported that 111/1 ratio of pyrene for... 

Complexants other than alcohols (e.g., amines, nitriles, tert-butyl compounds, surfactants, and multiple fluorophores) can also be detected by the method of Scheme 2 [279-284], Bohne and Yang have replaced alcohols with amino acids [285], although the zwitterionic charge distribution and increased steric requirements of the former lead to smaller stability constants of the ternary complex. Notwithstanding, tryptophan, leucine, and phenylalanine produce measurable changes in the I III ratio of pyrene emission, thereby allowing for their detection at mM levels. 

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