title: Prototropic interactions of pyrimidine nucleic acid bases with acridine: a spectroscopic investigation.
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.
authors: Chemical Sciences Division, Saha Institute of Nuclear Physics , 1/AF, Bidhannagar, Kolkata 700064, India.
authors: Manas Kumar
authors: MK
authors: Sarangi
authors: Ankita
authors: A
authors: Mitra
authors: Samita
authors: S
authors: Basu
mesh_terms: D000166:Acridines / Q000737:chemistry*; D003596:Cytosine / Q000737:chemistry*; D004579:Electron Transport; D007834:Lasers; D011743:Pyrimidines / Q000737:chemistry*; D013057:Spectrum Analysis; D013941:Thymine / Q000737:chemistry*; D014498:Uracil / Q000737:chemistry*
chemical_list: D000166:Acridines; D011743:Pyrimidines; D014498:Uracil; D003596:Cytosine; C030986:pyrimidine; D013941:Thymine