Regensburg 2007 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 10: INTERNAL SYMPOSIUM Scattering Experiments I
CPP 10.7: Talk
Tuesday, March 27, 2007, 11:45–12:00, H37
Protein Interactions in Aqueous Solution Studied by Small-Angle X-ray Scattering — •Fajun Zhang1, Maximilian Skoda1,2, Robert Jacobs3, Richard Martin4, Christopher Martin5, and Frank Schreiber1 — 1Institut für Angewandte Physik, Universität Tübingen, 72076 Tübingen, Germany — 2PTCL, University of Oxford, UK — 3CRL, University of Oxford, UK — 4Department of Physics, University of Bath, UK — 5SRS, Daresbury, Warrington, UK
We have studied protein interactions in two related systems by small-angle x-ray scattering: a series of pure protein solutions with various salt and protein concentrations, and mixtures of protein with oligo(ethylene glycol) (OEG) thiol decorated gold colloids. Structure factors derived from hard sphere potential, screened Coulomb potential, and square well potential, combined with an oblate ellipsoid form factor are used to fit the scattering intensities. An interaction phase diagram has been constructed as a function of ionic strength and protein concentration [1]. For the mixture of protein with functional gold colloid, we present evidence for an attractive interaction between OEG-decorated gold colloids and a repulsive interaction between gold colloid and protein. The attractive potential originates from a depletion force which strongly depends on the size of colloids and the concentration of protein, while the repulsive potential is due to the protein resistance of the OEG monolayer. Indeed, we observed the aggregation of gold colloids, when protein concentration is higher than a critical value.
[1] Zhang, F.; Skoda, M.W.A.; Jacobs, R.M.J.; Martin, R.A.; Martin, C.M.; Schreiber, F. J. Phys. Chem. B 2006, in press.