NMR Spectroscopic Study of a DNA Duplex with Mercury-Mediated T-T Base Pairs

Recently, we reported that T-T mismatches can specifically recognize Hg ^II (T-Hg ^II -T pair formation). In order to understand the properties of the T-Hg ^II -T pair, we recorded NMR spectra for a DNA duplex, d(CGCG TT GTCC) • d(GGAC TT CGCG), with two successive T-T mismatches (Hg ^II -binding sites). We assigned ¹ H resonances for mercury-free and di-mercurated duplexes, and performed titration experiments with Hg ^II by using 1D ¹ H NMR spectra. Because of the above mentioned assignments, we could confirm the existence of mono-mercurated species, because individual components gave independent NMR signals in the titration spectra.

Keywords:

• ¹H NMR
• Hg^II-mediated T-T base pair
• Titration
• Equilibrium

Acknowledgments

This article is dedicated to Professor Eiko Ohtsuka on the occasion of her 70th birthday.

This work was supported by a grant-in-aid for Scientific Research (C) (185501446) from the Ministry of Education, Culture, Sports, Science and Technology, Japan. AO was supported by a grant-in-aid for Scientific Research (B) (16350090), and by The Mitsubishi Foundation.

Notes

^a Chemical shifts are given in ppm.

^b Chemical shifts for H2 of adenosine, or H5 of cytidine, or the methyl proton of thymidine.

^c Chemical shifts for H8 of the purine residues or H6 of the pyrimidine residues.

^d Chemical shifts for H5′ and H5″. Stereospecific assignments were not carried out.

^a Chemical shifts are given in ppm.

^b Chemical shifts for H2 of adenosine, or H5 of cytidine, or the methyl proton of thymidine.

^c Chemical shifts for H8 of the purine residues or H6 of the pyrimidine residues.

^d Chemical shifts for H5′ and H5″. Stereospecific assignments were not carried out.