Structure effect of nucleotides in terbium(III)—nucleotide fluorescent reaction New evidence for the binding sites of terbium(III) on nucleotides

Upon addition of Tb³⁺ to 16 nucleotides and homopolynucleotides, all of them showed a characteristic green emission from Tb³⁺, but with much different intensity, upon excitation in the aromatic region of bases. The result suggested that nucleotides with at least one carbonyl group in nucleotide bases are better enhancers to the fluorescence of Tb³⁺. The complexes of ATP, GDP and GTP with Tb³⁺ are synthesized as two types of models. Guanine type nucleotides with one carbonyl group in the bases are the best enhancers, while adenine type nucleotides with no carbonyl group in the bases are poorest enhancers to the fluorescence of Tb³⁺. Comparing the IR spectra of ATP, GTP, GDP and their Tb³⁺ complexes suggested that C-6 carbonyl group in GTP and GDP may be involved in complex formation, which may be responsible for the effective energy transfer. This is further supported by comparing the UV spectra of ATP, Poly(A), GTP, and Poly(G) with their Tb³⁺ complexes in water solution.