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[S1050-0472(00)03204-9]

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Prion diseases are characterized by the accumulation of PrP(Sc), an aberrantly folded isoform of the host protein PrP(C). Specific forms of synthetic molecules known as dendrimers are able to eliminate protease-resistant PrP(Sc) in both an intracellular and in vitro setting. The properties of a dendrimer which govern this ability are unknown. We addressed the issue by comparing the in vitro antiprion ability of numerous modified poly(propylene-imine) dendrimers, which varied in size, structure, charge, and surface group composition. Several of the modified dendrimers, including an anionic glycodendrimer, reduced the level of protease resistant PrP(Sc) in a prion strain-dependent manner. This led to the formulation of a new working model for dendrimer/prion interactions which proposes dendrimers eliminate PrP(Sc) by destabilizing the protein and rendering it susceptible to proteolysis. This ability is not dependent on any particular charge of dendrimer, but does require a high density of reactive surface groups.

This paper presents a synthesis methodology for robots that have less than six degrees of freedom, termed constrained robots. The goal is to determine the physical parameters of the chain that fit its workspace to a given set of spatial positions. Our formulation uses the dual quaternion form of the kinematics equations of the constrained robot. Here we develop the theory and formulate the synthesis equations for the spatial RPR robot. Their solution ensures that the three dimensional workspace of this robot contains a given set of four spatial positions.

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