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Structural Heterogeneity in DNA: Temperature Dependence of 2-Aminopurine Fluorescence in Dinucleotides

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Abstract

The fluorescent base analogue 2-aminopurine is a sensitive probe for local dynamics of DNA. Its fluorescence is quenched by interaction with the neighboring bases, but the underlying mechanisms are still under investigation. We studied 2-aminopurine fluorescence in dinucleotides with each of the natural bases. Consistently, two of the four fluorescence-decay components depend strongly on temperature. Our results indicate that these components are due to the excited-state dynamics of a single conformational state. We propose a variation of the gating model in which transient unstacking occurs in the excited state.

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