I. Gryczynski, Z. Gryczynski, J. Lakowicz
Apr 1, 1999
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0
Influential Citations
30
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Quality indicators
Journal
Photochemistry and Photobiology
Abstract
Abstract— Topotecan is an antitumor agent with activity against a variety of cancers. We examined the steady‐state and time‐resolved fluorescence spectral properties of topote‐can with one‐and two‐photon excitation. Topotecan was found to display a high two‐photon cross section near 20 GM for wavelengths within the fundamental output of a Ti: sapphire laser, 800–880 nm. In frozen solution the anisotropies of topotecan are near the theoretical maxima for one‐photon and two‐photon excitation with colinear electronic transitions. The intensity and anisotropy decays of topotecan fluorescence were found to be homogeneous (single exponentials) in phosphate‐buffered saline and propylene glycol. The steady‐state and time‐resolved data indicate that topotecan binds to a double‐helical DNA oligomer d(AT)10 resulting in increased anisotropies and multiexponential intensity and anisotropy decays. Subnanosecond components in the anisotropy decay of the DNA‐topotecan complex suggest loose binding of the drug to DNA. Loose binding of topotecan to DNA is also revealed by accessibility of topotecan to collisional quenching by iodide.