Laser Light Scattering as an Indispensable Tool for Probing Protein Aggregation

Abstract

Protein misfolding and aggregation have emerged as significant problems in two quite different arenas. For the medical community, the spontaneous conversion of soluble proteins or protein fragments into fibrillar polymers with regular cross-sheet structure is linked to diseases as diverse as Huntington’s, Alzheimer’s, type II diabetes, and the prion diseases. For manufacturers of protein products, aggregation of proteins during processing, formulation, or storage results in a reduction in yield and off-specification products. Multiple biophysical tools are required for the elucidation of the mechanisms and pathways by which proteins misfold and aggregate. In this chapter, we turn our attention to one of these tools: laser light scattering. This noninvasive technique provides a means for measuring key size and shape properties of macromolecules in solution. Laser light scattering probes length scales on the order of 1–1000 nm, making it uniquely suited for detecting and characterizing soluble protein aggregates. Laser light scattering comes in two flavors: static and dynamic. From static light-scattering measurements, one can extract useful data on molecular weight and radius of gyration of proteins and protein aggregates in solution. The hydrodynamic diameter is obtained from dynamic light scattering. Given appropriate conditions and with more detailed data analysis, information about particle shape and characteristic dimensions, size distribution and polydispersity of populations of particles, and interparticle interactions can be obtained. Laser light-scattering studies have contributed to many investigations of protein misfolding and aggregation; a few of these studies are discussed.