How zinc ions shift and enhance the nucleotide's fluorescence spectra

Abstract

The intrinsic fluorescence of four DNA nucleotides is particularly weak and their optical emission spectra are mutually almost indistinguishable. Therefore, intrinsic fluorescence was never considered as a physical property that could be utilized for optical detection and differentiation of nucleobases. In this article, we show how complexation of DNA nucleotides with zinc cations could change this issue: it strongly enhances the nucleotide fluorescence and shifts the fluorescence spectrum maxima by different amounts for different nucleotides. A detailed study of fluorescence in Zn(II) complexes with individual nucleotides – 2′-deoxyadenosine 5′-monophosphate (dAMP), thymidine 5′-monophosphate (TMP), 2′-deoxyguanosine 5′-monophosphate (dGMP) and 2′-deoxycytidine 5′-monophosphate (dCMP) – has shown that the strongest fluorescence amplification undergoes dGMP for which the integrated fluorescence intensity increases by two orders of magnitude upon complexing with Zn(II). The fluorescence spectra of the Zn(II)–nucleotide complexes are resolved well enough to enable discrimination of the nucleotides according to their optical emission spectra.