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A Note on Protein Aggregation from Aqueous Solution

Juergen U. Keller, Institute of Fluid-and thermodynamics, University of Siegen, Paul-Bonatz Str. 9-11, Siegen, 57068, Germany

The aggregation of proteins from aqueous solution is a phenomenon of growing importance in several fields of biosciences, among them biotechnology, pharmacy, and medicine [1]. As aggregation may have many reasons normally related to (complex) protein – protein interactions, it is not easy to develop a unifying theory which would cover all aspects of this phenomenon. Hence it seems to be worthwhile to have a simple model at hand which would allow to describe the behavior of proteins in aqueous solution in the vicinity of a given thermodynamic state.

In this paper a simple statistical model of Langmuirian / BET type for aggregation of proteins is developed based on the idea of “self-adsorption” of proteins on proteins.

The model allows to characterize aggregation of a protein within a solution as kind of phase transition which is described by three parameters: a critical concentration of protein within the fluid phase, an aggregation enthalpy and a fractal exponent describing the geometry/topology of the protein aggregates.

The respective thermostatic equilibria relations and process equations are given and discussed with regard to the aggregation of insulin [2] to a certain extend.

[1] Sipe J. D., Cohen A. S., J. Struct. Biol., 2000, Vol. 130, p. 88.

[2] Dzwolak W. Ravindra R. Winter R., Hydration and Structure – The Two Sides of the Insulin Aggregation Process, Phys. Chem. Chem. Phys., 2004, Vol. 6, p. 1938.