Nucleic acid base specific quenching of coumarin-120-derivative in nucleotid-conjugates-photoinduced electron transfer

摘要

In nucleotid coumarin conjugates nucleic acid base specific quenching of the dye is observed. The lifetime of the coupled dye in aqueous solution decreases in the order: adenine (A)>cytosine(C)>thymine(T)>guanine(G). These differences in fluorescence properties of the label can be utilized to develop a new method for DNA sequencing with only one dye and one lane. The paper investigates whether quenching might result from photoinduced electron transfer. Thus redox potentials of several nucleosides and coumarin-120 were determined by cyclic voltammetry and polarography in dimethylformamide. It was found for the bases of 2$PRM@-deoxynucleosides, that G can be oxidized electrochemically (1,18 vs SCE), whereas A, C and T can be reduced (-2.69 V.-2.47 V and -2.38 V vs SCE). The correlation of the standard free energy ($Delta@G$+0$/) and log (k$-q$/) of intra- and intermolecular quenching constants, evaluated from Stern-Volmer plots, give an experimental hint, that the donor and acceptor properties of the fluorescent label are important for the specific quenching. Additional ground state interactions were found for some purine and pyrimidine bases.