Interfacial water and peptide adsorption

Note: Pizza served
Speaker: Roland Netz, Technical University of Munich

When: October 14, 2009 (Wed), 05:00PM to 06:00PM (add to my calendar)
Hosted by: Claudio Chamon

This event is part of the Biophysics/Condensed Matter Seminar Series.

Abstract:
The structural and dynamic properties of water at solid surfaces are relevant for many physico-chemical processes.
Insight can be gained from all-atomistic simulations of interfacial water that nowadays reach the experimentally
relevant length and time scales. This is demonstrated with a few examples:

i) Hydrophobic surfaces in contact with water show a pronounced depletion layer
with a thickness of a few Angstroms within which the water density is highly reduced1.
This layer leads to unusual static and kinetic properties including a finite slip length2.
ii) Many polypeptides readily adsorb on both hydrophobic and hydrophilic surfaces. Single molecule AFM experiments yield adsorption energies and point to an extremely high
mobility on hydrophobic surfaces. The dominant hydrophobic attraction can be quantitatively explained with classical MD simulations including explicit water. Both water structural effects and dispersion interactions contribute to this solvation attraction3.
iii) The friction coefficient of bound polymers is very low on hydrophobic substrates, which is traced back to the presence of a vacuum layer between substrate and water, which forms a lubricating cushion on which a polymer can glide. Conversely, friction forces on hydrophilic substrates are large and make determining the equilibrium binding constant in computer simulations impossible.[4]

[1] Interfacial Water at Hydrophobic and Hydrophilic Surfaces: Depletion versus Adsorption, J. Janecek and R.R. Netz, Langmuir 23, 8417 (2007) [2] Water slippage versus contact angle: a quasi-universal relationship, D.M. Huang, C. Sendner, D. Horinek, R.R. Netz, and L. Bocquet, Physical Review Letters (2008)
[3] Peptide adsorption on a hydrophobic surface results from an interplay of solvation, surface and intrapeptide forces, D. Horinek, A. Serr, M. Geisler, T. Pirzer, U. Slotta, S. Q. Lud, J. A. Garrido, T. Scheibel, T. Hugel, R. R. Netz, PNAS 105, 2842 (2008)
[4] Polypeptide friction and adhesion on hydrophobic and hydrophilic surfaces: A molecular dynamics case study, A. Serr, D. Horinek and R.R. Netz, Journal of the American Chemical Society 130, 12408 (2008)