Specific features of Zn2+, Co2+ and Ni2+ ion binding to DNA in alkaline solutions

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

Zinc–nucleotide complexes in alkaline solutions exhibit strong fluorescence enhancement and red shift, thus enabling an optical discrimination between the nucleotides.

Interaction of Zn(2+) ions with single-stranded polyU and polyC in neutral solutions

Effect of Zn(2+) ions on the conformation of single-stranded polynucleotides polyU and polyC in a wide temperature range at pH 7 was studied by differential UV spectroscopy and by thermal denaturation. The atoms coordinating Zn(2+) ions were determined (O4 and N3 in polyU and N3 in polyC). A three-dimensional phase diagram and its two-dimensional components were constructed for a polyC-Zn(2+) system. The phase diagram revealed a region in which ordered single-stranded structures, stabilized by Zn(2+)-mediated cross-links involving N3 atom of cytosine, are formed. The phase diagram also demonstrated that the behavior of the polyC-Zn(2+) system is similar to the effect of retrograde condensation observed in some binary solutions of simple liquids. A dependence of Zn(2+)-polyC binding constant on the metal ion concentration was obtained. The reason why zinc-induced transition of the sequences with adenine-uracil (AU) base pairs from A-form geometry to a metallized m-form requires higher pH compared to the sequences comprised of guanine-cytosine (GC) base pairs is explained. This information can be useful for the development of possible technological applications based on m-DNA.

Metallization of single-stranded polyI by Zn(2+) ions in neutral solutions

Metallization of single-stranded polyinosinic acid (polyI) by Zn(2+) ions at pH 7.0 was studied by differential UV spectroscopy at different temperatures. It was found that polyI is metallized at N7 and N1 atoms of hypoxanthine. The concentration dependence of the degree of binding of Zn(2+) ions to both N7 and N1 sites was obtained, and the corresponding binding constants were determined. Metallization of N1 occurs due to Zn(2+) substituting the imino protons and is effective not only at alkaline but also at neutral pH. This makes multistranded polyI-based systems more promising candidates for use in nanoelectronics than natural DNA sequences, metallization of which can be achieved only at alkaline pH.