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Original article (peer-reviewed)

Journal CHEMISTRY & BIODIVERSITY
Volume (Issue) 9(9)
Page(s) 2050 - 2063
Title of proceedings CHEMISTRY & BIODIVERSITY

Abstract

Deletion of the substituted pyrimidine ring in purine-2′-deoxynucleoside 5′-monophosphates leads to the artificial nucleotide analog dImMP2−. This analog can be incorporated into DNA to yield, upon addition of Ag+ ions, a molecular wire. Here, we measured the acidity constants of H2(dImMP)± having one proton at N(3) and one at the POequation image group by potentiometric pH titrations in aqueous solution. The micro acidity constants show that N(3) is somewhat more basic than POequation image and, consequently, the (H⋅ dImMP)− tautomer with the proton at N(3) dominates to ca. 75%. The calculated micro acidity constants are confirmed by 31P- and 1H-NMR chemical shifts. The assembled data allow many quantitative comparisons, e.g., the N(3)-protonated and thus positively charged imidazole residue facilitates deprotonation of the P(O)2(OH)− group by 0.3 pK units. Information on the intrinsic site basicities also allows predictions about metal-ion binding; e.g., Mg2+ and Mn2+ will primarily coordinate to the phosphate group, whereas Ni2+ and Cu2+ will preferably bind to N(3). Macrochelate formation for these metal ions is also predicted. The micro acidity constant for N(3)H+ deprotonation in the (H ⋅ dImMP⋅H)± species (pka 6.46) and the Mn+-binding properties are of relevance for understanding the behavior of dImMP units present in DNA hairpins and metalated duplexes.
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