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Updated: May 20, 2026

Sequence-specific and Selective Recognition of Double-stranded RNAs over Single-stranded RNAs by Chemically Modified Peptide Nucleic Acids
Published on: September 21, 2017
Prototropic interactions of pyrimidine nucleic acid bases with acridine: a spectroscopic investigation
Manas Kumar Sarangi1, Ankita Mitra, Samita Basu
1Chemical Sciences Division, Saha Institute of Nuclear Physics , 1/AF, Bidhannagar, Kolkata 700064, India.
Abstract:
In this article, we have investigated the interactions of three pyrimidine nucleic acid bases, cytosine (C), thymine (T), and uracil (U) with acridine (Acr), an N-heterocyclic DNA intercalator, through the changes in photophysics of Acr inside SDS micelles. Fluorescence of AcrH(+)* at 478 nm and its lifetime are quenched on addition of C, T, and U, while a concomitant increment of Acr* is observed only with C. However, the relative amplitude of Acr* increases with a simultaneous decrease in AcrH(+)* only with C. The fluorescence quenching of AcrH(+)* is explained by photoinduced electron transfer (PET), while changes in the relative contributions of Acr* and AcrH(+)* with C are due to associated excited-state proton transfer (ESPT). The rate of electron transfer (kET) is maximum for T, followed by U and C. The associated ESPT from AcrH(+)* is the reason behind the reduced efficiency of PET with C. The lack of proton transfer with T and U as well as the higher kET for T compared to U are explained by keto-enol tautomerization and subtle changes in the structure and geometry of the pyrimidine bases.
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