Multinuclear NMR Study of the Conformational Changes in MepdG and dGpMe upon Interaction with Mg2+, Zn2+ and Hg2+ Ions Reveals the Strengthening of the Anomeric Effect by Soft M2+ Ions
✍ Scribed by Matjaž Polak; Janez Plavec
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 380 KB
- Volume
- 1999
- Category
- Article
- ISSN
- 1434-1948
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✦ Synopsis
A conformational study is reported on 2Ј-deoxyguanosine 5Ј-pseudorotational equilibrium, whereas the interactions of Zn 2+ and Hg 2+ ions with N7 resulted in the shift towards N-methylmonophosphate [MepdG (1)] and 2Ј-deoxyguanosine 3Ј-methylmonophosphate [dGpMe (2)] and their interactions type pseudorotamers which can be explained by the strengthening of the anomeric effect as softer metal ions bind with Mg 2+ , Zn 2+ and Hg 2+ ions. The conformation of MepdG (1) and dGpMe (2) in D 2 O solution was inferred from vicinal to N7 and make the imidazole moiety less electron-rich. (ii)
The binding of divalent metal ions to MepdG (1) and dGpMe proton-proton, proton-phosphorus and carbon-phosphorus NMR coupling constants and nuclear Overhauser effects (2) causes a shift of the syn q anti equilibrium towards anti, which is larger for softer Zn 2+ than for harder Mg 2+ ions. (iii) (NOE). The chemical shift changes showed that hard Mg 2+ ions interact preferentially with the phosphate oxygen atoms
The conformational equilibrium across the C4Ј-C5Ј bond (γ torsion) in dGpMe ( 2) is not affected by the increased in MepdG (1), whereas in the case of dGpMe (2) the interaction with the phosphate oxygen atoms competes with concentration of M 2+ ions. (iv) β t conformers are preferred by ca. 77% in aqueous solution of MepdG (1) and only small the interaction to the C6=O carbonyl group. Softer Zn 2+ and Hg 2+ ions were found to show strong binding affinity towards changes of ca. 1 percentage point in β t population have been found upon metal ion binding to MepdG ( 1). (v) The two-N7 in both MepdG (1) and dGpMe (2). Analysis of J coupling constants and NOEs measured as a function of metal ion state ε t q ε -conformational equilibrium is biased towards ε t rotamers by 63.5% in dGpMe (2). Interaction of hard Mg 2+ concentration revealed that: (i) N q S pseudorotational equilibria are biased towards C2Ј-endo pseudorotamers in and softer Zn 2+ or Hg 2+ ions with dGpMe (2) resulted in the minor increase (Ͻ 3 percentage points) in the population of M 2+ -free MepdG (1) and dGpMe (2) by 68% and 75% at 298K, respectively. Titration of MepdG (1) and dGpMe (2) ε t conformers. with Mg 2+ ions caused no observable changes in N q S MepdG (1) and dGpMe (2), which consist of all the essen- [a] National Institute of Chemistry, puckering mode can be defined by AltonaϪSundaralingam Hajdrihova 19, SI-1115 Ljubljana, Slovenia parameters [4,5] which are the phase angle of pseudorotation