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Article

Adsorption of Pathogenic Prion Protein to Quartz Sand

Supporting Info

Xin Ma,^†^‡ Craig H. Benson,^‡ Debbie McKenzie,^§ Judd M. Aiken,^§ and Joel A. Pedersen*^†^‡

Department of Soil Science, University of Wisconsin, Madison, Wisconsin 53706, Department of Civil and Environmental Engineering, University of Wisconsin, Madison, Wisconsin 53706, Department of Comparative Biosciences, University of Wisconsin, Madison, Wisconsin 53706, and Molecular and Environmental Toxicology Center, University of Wisconsin, Madison, Wisconsin 53706

Environ. Sci. Technol., 2007, 41 (7), pp 2324–2330

DOI: 10.1021/es062122i

Publication Date (Web): March 6, 2007

†

Department of Soil Science.

‡

Department of Civil and Environmental Engineering.

Department of Comparative Biosciences.

Corresponding author phone: (608) 263-4971; fax: (608) 265-2595; e-mail: japedersen@soils.wisc.edu.

Molecular and Environmental Toxicology Center.

Abstract

Management responses to prion diseases of cattle, deer, and elk create a significant need for safe and effective disposal of infected carcasses and other materials. Furthermore, soil may contribute to the horizontal transmission of sheep scrapie and cervid chronic wasting disease by serving as an environmental reservoir for the infectious agent. As an initial step toward understanding prion mobility in porous materials such as soil and landfilled waste, the influence of pH and ionic strength (I) on pathogenic prion protein (PrP^Sc) properties (viz. aggregation state and ζ-potential) and adsorption to quartz sand was investigated. The apparent average isoelectric point of PrP^Sc aggregates was 4.6. PrP^Sc aggregate size was largest between pH 4 and 6, and increased with increasing I at pH 7. Adsorption to quartz sand was maximal near the apparent isoelectric point of PrP^Sc aggregates and decreased as pH either declined or increased. PrP^Sc adsorption increased as suspension I increased, and reached an apparent plateau at I 0.1 M. While trends with pH and I in PrP^Sc attachment to quartz surfaces were consistent with predictions based on Born-DLVO theory, non-DLVO forces appeared to contribute to adsorption at pH 7 and 9 (I = 10 mM). Our findings suggest that disposal strategies that elevate pH (e.g., burial in lime or fly ash), may increase PrP^Sc mobility. Similarly, PrP^Sc mobility may increase as a landfill ages, due to increases in pH and decreases in I of the leachate.