Eximer fluorescence studies

The self-assembly of this fundamental building block of chromatin is a topic of enduring interest. DNase I digestion experiments as well as spectroscopic studies indicate that nucleosome core particles can be reconstituted by salt-jump (i.e., diluting NaCl concentration from 2.0 to 0.2 M) or by direct mixing of histones and DNA at the lower salt concentration. Daban and Cantor used the increase in eximer fluorescence to investigate the reassembly process in terms of a two-state model ... 

Eximer Fluorescence. Since Forster and Kasper discovered concentration-dependent long-wavelength emission resulting from association of an electronically excited pyrene molecule with another ground state pyrene molecule,39 the phenomenon of excimer fluorescence has been studied extensively.40 The mechanism for excimer formation and emission can be represented by... 

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]. 

Nearly all the nonfluorescent emission bands reported in these studies have been found at longer wavelengths than the expected fluorescence. They have been variously ascribed to eximers6,15 or to phosphorescence1315 of the electroactive substance. Some apparently do not arise from the electroactive compound itself.16 On oxidation of the pyrene anion radical with Wurster s blue perchlorate, an emission band was obtained which corresponded closely to the known pyrene eximer emission.15 Several spectra obtained from polycyclic aromatic hydrocarbons by electrochemical treatment at constant applied voltage have... 

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