Thermodynamic properties of hydration water near solid surfaces and in solutions of macromolecules

• Applicant: Dr. Alla Oleinikova
• Subject Area: Theoretical Chemistry: Electronic Structure, Dynamics, Simulation
• Term: from 2009 to 2012
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 150857372

• Final Report Year: 2012

Final Report Abstract

The principal goals of this project were: to determine the thermodynamic properties of hydration water near various surfaces by simulations; to establish dependence of these properties on temperature, pressure, surface characteristics and on the state of hydrogenboned network of hydration water; to compare the main regularities in the behaviour of the thermodynamic properties of water near surfaces with those of lattices and Lennard-Jones (LJ) fluids. Worsening of water-water interactions near a surface due to the missing neighbour effect causes density depletion of liquid water in wide ranges of temperature and water-surface interaction, including hydrophilic surfaces. This effect weakens upon increasing surface curvature. Similarly to lattices and LJ fluids, the temperature dependence of the liquid water density along the liquid-vapour coexistence becomes more linear-like that causes strong increase of the thermal expansion coefficient , especially near hydrophobic surfaces. This effect is more pronounced for water due to the directionality of water-water interactions and due to the absence of the liquid density maximum for hydration water. Constant volume specific heat of liquid water practically does not change near surfaces. Thus, the experimentally observed increase of the constant pressure specific heat upon solvation of hydrophobic solutes should be attributed to the increase of the thermal expansion coefficient. The break of the spanning network of hydration water upon heating has no effect on its thermodynamic properties near structureless surfaces. Near peptides, this break causes step-like changes in the temperature dependences of some thermodynamic properties of hydration water: constituents of the heat capacity and thermal expansion coefficient. These changes should be attributed to the particular structure of the peptide´s backbones, which promotes cooperative hydration of a polymer chain.

Publications

• The temperature dependence of the heat capacity of hydration water near biosurfaces from molecular simulations, Eurphys. Lett. 90, 36001 (2010)
  A. Oleinikova, I. Brovchenko, and G. Singh
  
• Volumetric properties of human islet amyloid polypeptide in liquid water, Phys. Chem. Chem. Phys. 12, 4233-4238 (2010)
  I. Brovchenko, M.N. Andrews and A. Oleinikova
  
• Thermal stability of the hydrogenbonded water network in the hydration shell of islet amyloid polypeptide, J. Phys.: Condens. Matt. 23, 155105 (2011)
  I. Brovchenko, M. N. Andrews and A. Oleinikova
  
• Hydrogen-bonded network of hydration water around model solutes, Phys. Chem. Chem. Phys., 14, 5686–5694 (2012)
  A. Oleinikova and I. Brovchenko