The Molecular Sociology of Proteins

Bramie Lenhoff from Univ of Delaware

Protein solutions are ubiquitous in bioprocessing, structural biology and in nature, making it important to understand and predict their physical and thermodynamic properties, including formation of dense phases such as precipitates, crystals, gels and aggregates.  Although such capabilities for small molecules are routinely taught to undergraduates, proteins are macromolecules and so are generally treated as colloidal particles, with their properties understood using methods generally applied in studying soft matter.  However, the anisotropic shape and chemical character of protein molecules, on which extensive information down to the atomic level is available from X-ray crystallography, add considerable complexity, especially in describing intermolecular interactions and phase behavior – the molecular sociology.  This presentation will explore where the use of simplified colloidal models of proteins is or is not reasonable, with an emphasis on the structure and evolution of amorphous dense phases.  Scattering and microscopy data show structural similarities to colloidal gels, but because of the anisotropy of intermolecular interactions, the range of behavior can be much richer than that observed for spherical particles.