tailieunhanh - INTERFACIAL AND CONFINED WATER Part 8

Điều này bao gồm hai yếu tố: sự xuất hiện của một phân tử nước với số lượng lớn như động lực và sự tương quan mạnh mẽ về chuyển động của nước khi hình thành một mạng lưới trải rộng. | 214 Interfacial and confined water that affects dielectric properties of the system. This includes two factors appearance of a water molecule with bulk-like dynamics and strong correlation of water motions upon formation of a spanning network. The latter factor causes noticeable increase in the dielectric constant of the system that provides screening of the charged groups of a biomolecule and accordingly promotes its dynamics. As we discussed in Section conductivity of biosystems changes in a drastic way at the percolation threshold. This evidences that a spanning water network is an effective medium for the charge transfer along biosurfaces. Transfer of ions or protons may play some special role in biological function. Besides a spanning water network may be an effective medium for the transfer of metabolites see Section 6 which also makes its existence necessary for biological function. In this section we have considered mainly properties of single water molecules and ions in hydration shells. Further studies are necessary to clarify the role of the specific properties of a spanning water network in a biological function. 8 States of interfacial water in fully hydrated biosystems In dilute aqueous solutions biomolecules are completely covered by water molecules. The structure of water near a boundary essentially differs from the structure of bulk water see Sections 2 and 5 . Specific water structure is seen in one or two water layers near hydrophilic surfaces whereas the rest of liquid water is bulk-like. This is also the case for the surfaces of biomolecules which allow consideration of hydration water as a separate subsystem. Conformational transitions and aggregation of biomolecules occur in dilute solution due to variations of temperature and or pressure and due to additions of some cosolvents. It is natural to expect that these biologically important processes are related to the changes in the state of hydration water shell. First we consider the effect