| Centre
Paris-Saclay
| | | | | | | webmail : intra-extra| Accès VPN| Accès IST | English
Univ. Paris-Saclay
Which properties of biological (hydration) water enable biological functions ?
Alla Oleinikova
University of Dortmund
Lundi 21/09/2009, 11:00
NIMBE Bât 125, p.157, CEA-Saclay

Version:1.0 StartHTML:0000000183 EndHTML:0000011187 StartFragment:0000002483 EndFragment:0000011151 SourceURL:file://localhost/Users/pguenoun/Documents/S%C3%A9minaires/alla.doc

The crucial role of water in biological functions is well-recognized,

numerous questions concerning the physical mechanisms behind the

importance of water for life remains unanswered. Biofunctions are possible

when the network of hydration water spans the surface of a biomolecule.

Such network may be broken upon dehydration or upon heating and this

process may be described by percolation theory. To clarify the physical

mechanisms of the crucial role of a spanning water network for

biofunctions, various properties should be studied when crossing the

percolation threshold. Dynamic coupling of protein and water dynamics is

maximal at hydration levels, corresponding to the formation of a spanning

network (monolayer) of hydration water. Water molecules strongly bounded

to the biosurface due to Coulombic or H-bond interaction show stretched

exponential rotational dynamics with large relaxation times, whereas

weakly-bound biological water shows faster bulk-like rotational dynamics.

Appearance of weakly-bound biological water upon hydration results in

drastic increase of the dielectric constant and screening of the Coulombic

interactions. This facilitates both conformational dynamic of biomolecules

and dissociation of counterions adjusted to the charged groups of

biomolecules.  Break of the spanning network of biological water upon

heating occurs in the temperature range, which is surprisingly close to

the typical temperatures of heat denaturation or unfolding of

biomolecules.

 

 

Contact : Patrick GUENOUN

 

#26 - Mise à jour : //

 

Retour en haut