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Bisimidazoacridones: Effect of Molecular Environment on Conformation and Photophysical Properties
Author(s) -
Tarasov Sergey G.,
CasasFinet Jose R.,
Cholody Wieslaw M.,
Michejda Christopher J.
Publication year - 1999
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1999.tb08253.x
Subject(s) - chromophore , chemistry , fluorescence , photochemistry , intramolecular force , fluorescence spectroscopy , micelle , time resolved spectroscopy , aqueous solution , spectroscopy , förster resonance energy transfer , macromolecule , molecule , chemical physics , stereochemistry , organic chemistry , biochemistry , physics , quantum mechanics
Bisimidazoacridones (BIA) are highly selective antineoplastic and antiviral agents. Ultraviolet‐visible spectroscopy and steady‐state and time‐resolved fluorescence spectroscopy studies were carried out to probe the behavior of BIA in aqueous and nonaqueous (organic solvents, colloid micelles) solutions. Three ranges of fluorescence lifetimes were revealed: ˜0.2‐0.5 ns (presumably reflecting the chromophore–chromophore interaction), ˜1–5 ns (interpreted as linker‐perturbed chromophore decay) and ˜6–12 ns (nonperturbed chromophore decay). The pre‐exponential and steady‐state contributions of these components to the decay signal as well as the data on steady‐state fluorescence intensities, wavelength maxima and bandwidths showed that the BIA conformations in solution were sensitive to the environment and influenced strongly by their propensity to minimize hydrophobic interactions. In water, the molecules tend to adopt condensed conformations that bring the two imi‐dazoacridone moieties into close proximity (resulting in intramolecular fluorescence energy transfer), while in nonaqueous systems the conformations become more relaxed. The transfer from a polar to more lipophilic environment of macromolecules is suggested to be the main driving force for binding of BIA to biomacromolecules, such as nucleic acids.