Hofmeister series and ionic effects of alkali metal ions on DNA conformation transition in normal and less polarised water solvent

Abstract

Normal and less polarised water models are used as the solvent to investigate Hofmeister effects and alkali metal ionic effects on dodecamer d(CGCGAATTCGCG) B-DNA with atomic dynamics simulations. As normal water solvent is replaced by less polarised water, the Hofmeister series of alkali metal ions is changed from Li⁺ > Na⁺ ≃ K⁺ ≃ Cs⁺ ≃ Rb⁺ to Li⁺ > Na⁺ > K⁺ > Rb⁺ > Cs⁺. In less polarised water, DNA experiences the B→A conformational transition for the lighter alkali metal counterions (Li⁺, Na⁺ and K⁺). However, it keeps B form for the heavier ions (Rb⁺ and Cs⁺). We find that the underlying cause of the conformation transition for these alkali metal ions except K⁺ is the competition between water molecules and counterions coupling to the free oxygen atoms of the phosphate groups. For K⁺ ions, the ‘economics’ of phosphate hydration and ‘spine of hydration’ are both concerned with the DNA helixes changing.

Keywords:

• Hofmeister effect
• ionic effects
• molecular liquids
• less polarised solvent
• DNA

Additional information

Funding

This work was supported by the National Natural Science Foundation of China [grant number 11025524], [grant number 11161130520]; National Basic Research Programme of China [grant number 2010CB832903]; the European Commission's 7th Framework Programme (FP7-PEOPLE-2010-IRSES) [grant agreement project number 269131].