Paper Number
BB27 

Session
Biomaterials and Biological Systems

Title
Viscosity and short time dynamics of concentrated solutions of proteins interacting with a short range attractive and long range repulsive interaction

Presentation Date and Time
October 7, 2014 (Tuesday) 4:25

Track / Room
Track 2 / Commonwealth B

Authors (Click on name to view author profile)

1. Godfrin, Paul D. (University of Delaware)
2. Hong, Kunlun (ORNL, Center for Nanophase Materials and Sciences)
3. Porcar, Lionel (ILL, Large Scale Structures Group)
4. Falus, Peter (ILL, Time of Flight and High Resolution Group)
5. Wagner, Norman J. (University of Delaware, Department of Chemical and Biomolecular Engineering)
6. Liu, Yun (NIST, NIST Center for Neutron Research)

Author and Affiliation Lines (in printed abstract book)
Paul D. Godfrin¹, Kunlun Hong², Lionel Porcar³, Peter Falus⁴, Norman J. Wagner¹, and Yun Liu^5
1Department of Chemical and Biomolecular Engineering, University of Delaware, Newark, DE; ²Center for Nanophase Materials and Sciences, ORNL, Oak Ridge, TN; ³Large Scale Structures Group, ILL, Grenoble, France; ⁴Time of Flight and High Resolution Group, ILL, Grenoble, France; ⁵NIST Center for Neutron Research, NIST, Gaithersburg, MD

Speaker / Presenter 
Godfrin, Paul D.

Text of Abstract
Concentrated colloidal dispersions interacting with a short range attractive and long range repulsive interaction are currently of significant scientific and technological interest as they can exhibit intermediate range order as well as significant viscosities. Such systems are capable of producing clustered fluid phases in which reversible, thermodynamically stable aggregates of finite size exist in equilibrium with monomers. Clustered fluids are formed by the balance of the competing potential features and are thought to be especially prevalent in concentrated protein solutions. Of particular importance in biotechnology is the effect of this fluid structure on the viscosity and diffusivity of proteins in solution. Recent studies have linked the formation of clusters in solutions of lysozyme and monoclonal antibodies to a substantial increase in solution viscosity (Biophys. J. 105:720, 2013). The goal of our work is to quantify the effect of intermediate range order and cluster formation on the viscosity of model protein solutions. Here we present experimental results for lysozyme, which is selected because of its availability, stability, and globular structure, the latter enabling quantitative comparison to models. Zero shear viscosity is obtained by microrheological measurements to avoid artifacts of interfacial rheological effects. A strong divergence of zero shear viscosity is observed for volume fractions well below that for hard sphere dispersions. The fluid microstructure and protein short time-self diffusion are measured across a broad range of conditions by small angle neutron scattering (SANS) and neutron spin echo (NSE), respectively. Previously validated models that include explicit hydrodynamic, Brownian, and interaction contributions to the viscosity fail to account for the large viscosity rise with concentration. However, this excessive viscosity rise can be semi-quantitatively predicted when protein clustering is properly accounted for and effective cluster-cluster interactions properly included.