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Accueil du site > Séminaires, conférences > Séminaires du LIP > Séminaires en 2005 > Probing DNA hydration by volumetric means.

Probing DNA hydration by volumetric means.

Date : 12/09/2005 à 14h00

Intervenant :
- Tigran CHALIKIAN, Departement of Pharmaceutic Sciences, Leslie Dan Faculty of Sciences, University of Toronto, Canada.

Résumé : Hydration represents a major thermodynamic factor that plays a dominat role in governing the conformational preferences of nucleic acids as well as modulating ligand-DNA and protein-DNA interactions. However, the problem of hydration is very difficult to tackle since there are not many experimental techniques that enable one to discriminate between water of solute hydration and bulk water. In this respect, volumetric measurements provide such a possibility. Volume and compressibility are thermodynamic observables that are sensitive to solute hydration. These observables can be used not only to determine the net amount of water molecules affected by solvent (the quantity of hydration) but also to discriminate between water molecules solvating charged, polar, and nonpolar atomic group (the qulity of hydration). Volumetric measurements have been used to investigate the hydration properties of DNA and RNA duplexes as welle as their low molecular weight analogs. Nucleic acid hydration appears to be conformation-, composition, and sequence-dependent. However, there is no simple correlation between DNA hydration and its primary nuceotide sequence. This observation may in part be related to formation by some periodic sequences of cooperative hydration networks involving water molecules beyond the first coordination sphere. In a recent study, volume and compressibility measurements have been applied to probing hydration of counterions in the vicinity of single- and double-stranded DNA and RNA. These measurements have revealed that the poly(dGdC)poly(dGdC), poly(dldC)poly(dldC), and poly(rl)poly(rC) duplexes and single-stranded poly(rU) do not signicantly influence the hydration properties of their condensed counterions. In the vicinity of these polymers, counterions retain their full hydration shells (within +/- 15 %). By contrast, counterions condensed around the poly(dAdT)poly(dAdT), poly(rA)poly(rU), and poly(rG)poly(rC) duplexes are significantlydehydrated and retain, respectively, only 65 +/- 18%, 34 +/- 21% and 33 +/- 9% of their original hydration shells. In general, volumetric data provide important new information that ultimately may help one understand the central role that hydration and counterions play in modulating the conformational preferences of nucleic acids and the energetics of DNA recognition events.