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Specific Recognition of Single-Stranded Regions in Ultraviolet-Irradiated and Heat-Denatured DNA by Tryptophan-Containing Peptides

Jean-Jacques Toulme, Michel Charlier and Claude Helene
Proceedings of the National Academy of Sciences of the United States of America
Vol. 71, No. 8 (Aug., 1974), pp. 3185-3188
Stable URL: http://www.jstor.org/stable/63217
Page Count: 4
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Specific Recognition of Single-Stranded Regions in Ultraviolet-Irradiated and Heat-Denatured DNA by Tryptophan-Containing Peptides
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Abstract

Fluorescence studies of the binding of peptides containing lysyl and tryptophyl residues to nucleic acids show that two types of complexes are formed. One of them involves a direct interaction of the tryptophyl ring with nucleic acid bases, which leads to fluorescence quenching. Comparison with proton magnetic resonance and circular dichroism data indicates that this fluorescence quenching is due to a stacking of the indole ring with bases. Quantitative analysis of fluorescence data leads to the conclusion that stacking is favored in single-stranded regions of DNAs, which are produced either by heating or by UV-irradiation of the native DNA sample. The binding of the peptide Lys-Trp-Lys is about ten times tighter in these single-stranded regions as compared with double-stranded ones. A short tripeptide such as Lys-Trp-Lys is, therefore, able to discriminate between single-stranded and double-stranded regions. Moreover, bound peptide molecules photosensitize the splitting of thymine dimers in UV-irradiated DNA, thus providing a model for DNA photoreactivation.

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