Abstract

After a brief overview of the multiple and competing interactions in soft matter, and a short introduction to how information on the interactions and the resulting correlations can be obtained from elastic and inelastic X-ray and neutron scattering experiments (complemented by in-situ (under water) IR and UV/vis spectroscopy), we will discuss selected aspects of protein interactions.

These include the effect of ionic strength on the effective interaction potential in dense aqueous solutions (transition from screened Coulombic to effective hard sphere; F. Zhang et al., J. Phys. Chem. B 111 (2007) 251), efforts to “locate” the ionic cloud around proteins and near surfaces, and experiments to determine the microscopic and macroscopic dynamics of protein solutions while undergoing the denaturing transition. Particular attention will be given to the recent discovery of “reentrant condensation” in proteins (F. Zhang et al., Phys. Rev. Lett. 101 (2008) 148101).

We will also discuss our efforts to determine the protein solution density profile near a solid wall functionalised by a self-assembled monolayer and the interaction of different functionalities with water (M. Skoda et al., Langmuir 23 (2007) 970; M. Skoda et al., Langmuir, (2009)).