Proteins seen from a colloid physicist's view point

by Prof. P. Schurtenberger (University of Fribourg, Switzerland)

Tuesday 29 Apr 2008, 16:00 → 17:00 Europe/Rome

Aula M. Conversi (Dip. Fisica Edificio G. Marconi)

Recent developments in the description of colloids with short-ranged attraction have led to fascinating findings such as metastable liquid-liquid phase separation, (co-)existence of attractive and repulsive glasses and the formation of dynamically arrested states (transient gels). The emerging new glass paradigm has been successfully applied to more complex soft matter, i.e., colloid-polymer mixtures or concentrated protein solutions. It has often been speculated that globular proteins possess a short-ranged attractive potential, and that simple models from colloid science could be used to interpret their complex phase diagrams. Understanding interactions and phase transitions in protein solutions is for example essential in any attempt to go beyond a trial and error approach in protein crystallization, one of the most disturbing bottlenecks in life sciences. This has been a major driving force in recent attempts to use analogies between proteins and colloids. Moreover, issues such as interparticle interaction, aggregation, cluster and crystal formation and dynamical arrest in protein solutions have to be seen in a broader context, since they are of central importance to a variety of topics. There are in fact reasons to classify a number of apparently disparate diseases as "condensation" (or molecular aggregation) diseases. Examples of such condensation diseases include the late phase of diabetes mellitus, Alzheimer's disease and others, and there is growing evidence that the common, most important denominator of various condensation diseases derives from an intermolecular interaction that is in part attractive and in part repulsive. I will thus report on a critical re-examination of the different scenarios proposed for the interplay between phase separation and dynamical arrest in colloidal suspensions, and try to apply these findings to protein solutions.