Dresden 2006 – scientific programme

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CPP: Chemische Physik und Polymerphysik

CPP 11: POSTER Disperse Polymer Systems

CPP 11.17: Poster

Tuesday, March 28, 2006, 17:00–19:00, P3

In-situ Monitoring of Pressure-Induced Aggregation of beta-Lactoglobulin — •Albert Baars¹, Leszek Kulisiewicz¹, Ronald Gebhardt², Wolfgang Doster², and Antonio Delgado¹ — ¹Technische Universität München, Lehrstuhl für Fluidmechanik und Prozessautomation, D-85350 Freising — ²Technische Universität München, Physikdepartment E13, D-85747 Garching

At pressures up to 1 GPa, bovine beta-Lactoglobulin (B-Lg) in aqueous solution can undergo reversible and irreversible conformational changes, which lead to altered interactions between the dissolved protein molecules. This work investigates the impact of pressures up to 600 MPa on aqueous B-Lg solution by an in-situ rolling ball viscosimeter and by in-situ dynamic light scattering for mass fractions up to 6 % at 20 ^∘C and pH 7. Between 0.1 and 100 MPa, the results reveal negligible changes in relative viscosity while in the range of 100 - 350 MPa the viscosity rises up to the twice of the initial value. At higher pressures only a slight increase appears. These findings can be deduced from aggregation of monomers and dimers to oligomers. Between 100 and 300 MPa an increase in hydrodynamic radius from 1.8 to 7.4 nm has been observed. In literature it is known that pressures higher than 100 MPa induces conformational changes of B-Lg protein. These lead to a reduction of negative surface charge due to the exposure of hydrophobic tryptophan residues to the solvent. In addition, the SH group from Cys 121 moves to the protein surface. This enables aggregation by formation of hydrophobic and disulfide bonds. After pressure release, the latter are retained leading to an irreversible increase in relative viscosity.