Acridine, fluorescence spectrum

When acridane 1 is oxidized by dibenzoyl peroxide in propanol/ water in acid or neutral medium, there occurs chemiluminescence whose emission spectrum matches the fluorescence spectrum of acridinium cation (protonated acridine) 2. As radical scavengers have no influence... 

The fluorescence spectrum of the tris-acridine cryptand A-13 shows the characteristic monomer and excimer bands. Upon complexation with various organic anions (carboxylates, sulfonates, phosphates), the monomer band increases at the expense of the excimer band. The stability of the complexes depends on the contribution of the electrostatic and hydrophobic forces and on the structural complementarity. Stability constants of the complexes ranging from 103 to 107 have been measured. In particular, A-13 binds tightly to mono- and oligonucleotides, and it can discriminate by its optical response between a pyridimic and a purinic sequence. 

Acridine adsorbed on SG800A shows a similar fluorescence spectrum with that on SG200A. The apparent fluorescence intensity is reduced but the spectral shape is quite identical with that of acridine adsorbed on SG200A. These observations are consistent with the decrease in silanol groups in SG800A than in SG200A. 

Fluorescence studies of the commercially important l,3-diphenyl-2-pyrazoline derivatives have been extended to a wide range of phenyl- and methyl-substituted derivatives. The fluorescence yields in non-polar solvents are all close to unity, with the exception of l,3,5,5-tetraphenyl-2-pyrazoline. This is not the case in methanol, when a large variation in yields is observed.85 (See the section on oxidation for other photochemical processes in these compounds.) By an examination of the fluorescence spectra and fluorescence excitation spectra of 9-amino-acridine at 4.2 K, the fine-structure fluorescence spectrum of the neutral molecule has been identified and investigated using laser excitation.88... 

Another method, also applicable to the first excited singlet state, depends upon the variation of the fluorescence spectrum with pH, and is best illustrated by an example. The acridinium ion, AcrH", has pK — 5.45 in its normal state. It exhibits a green fluorescence in acid solution, attributable to the cation, and this remains unchanged with increasing pH up to about pH = 10, although the acridine has been converted almost entirely into the free base. This is explicable if the pK of the excited state is much greater than 5, so that in the pH range 7-10 the process is... 

Anthracene has also been used as an acceptor (Fig. 10). In solution, 26 emits a single fluorescence band that is somewhat structured in nonpolar solvents and becomes broad and structureless with increasing polarity [58]. The strongly hindered molecule 27 also exhibits a similar behavior, but its absorption spectrum is better structured [59]. The rate of formation of a charge transfer state is higher for 27 than for 26. Based on this observation, it appears that the twist around the anthryl-phenyl C-C bond plays a significant role in the fluorescence profile of the probes [60]. Acridines, such as 28, behave similarly to anthracene except that acridine is a better electron acceptor [61]. 

The film remaining after extensive bleaching (where the bleaching curves of Figure 5 are flat) still contains some acridine as judged by the weak blue fluorescence, but the absorption spectrum shows only a small bump near 250nm on top of an otherwise featureless curve. 

The fluorescence excitation spectrum of acridine in O.IN sulfuric acid has a band characteristic of acridinium cation at about 25000 cm, but on the other hand, acridine in ethanol has no band below 25000 cm" (see Fig. 8). The fluorescence excitation spectra of acridine both on SG200V and SG200A have a band near 25000 cra . These findings indicate that a proton is transferred to acridone from silanol groups in its ground state as a result of adsorption on the silica gel surface. The emission of acridine adsorbed on silica gel are reasonably assigned to the protonated species of acridine. 

Fusion of a benzene ring to a heterocyclic nucleus causes a bathochromic shift and increases the intensity of absorption. Thus, quinoline, isoquinoline, indole and quinolium and isoqumolium ions fluoresce in the ultra-violet. Acridine, acridone and carbazole exhibit visible fluorescence. Porphyrin18 and some of its derivatives are characterized by narrow well-defined vibrational bands and their fluorescence bands are in the red region of the spectrum. 

One of the few examples of lipid domains observed in living cells is the detection of CL in membranes of E. coli by the fluorescent dye 10-/V-nonyl acridine orange [1]. This reagent has a higher affinity for CL than other anionic lipids and association with CL induces a shift from green to red in the emission spectrum of the compound. Spectral shift upon... 

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