Technical Abstract. An asymmetric field flow fractionation device with on-line light scattering detectors, both static and dynamic, will permit high-resolution measurements of the size and molecular weight distributions of particles and assemblies. The system, which can handle aqueous or non-aqueous samples, will benefit these primary projects: formation of amyloid fibrils, which is a key process in Alzheimer's disease; responsive dendrimer superstructures designed to trap and release guests, such as drugs, toxins, and reagents, on command; early assembly of precursors to noncovalently stabilized polymer gels with potential as nanoscale scaffolds; evaluation of silica-polypeptide composite particles designed to produce responsive colloidal crystals; and, interactions in polymer-clay composites being developed for artificial skin applications. Secondary projects include characterization in support of virus preparation and function, physicochemical behavior of polyelectrolytes, and novel cone-shaped vesicles. The large size and often-delicate nature of the particles of interest makes them difficult or impossible to characterize by gel permeation chromatography. Other competing methods, such as cryo electron microscopy, are sometimes subject to preparation artifacts or undersampling errors. Most of the particles to be investigated carry an electrical charge; therefore, the request includes equipment to measure zeta potential, which is related to the effective charge on a molecule or particle in solution. This also permits routine biophysical measurements, such as the isoelectric point of proteins and subtle changes in their size under biologically relevant conditions. The new equipment will permit an older light scattering device to be retired and then reborn in the hands of student designers. The outcome will be an instrument that transcends commercially available designs for applications such as microrheology and rapid self-assembly.
The requested equipment can measure the size and mass of nanoparticles, polymers and their aggregates, both synthetic and naturally occurring. For example, Alzheimer's disease is thought to progress through the accretion of very small protein fragments into huge structures. The requested equipment will help assess the efficacy of drug candidates designed to intercept this process. The very same equipment will be used to characterize new synthetic materials that have the potential to carry drugs, remove environmental toxins, or isolate new materials in optically pure form. One component of the request is not widely available in publicly accessible laboratories. Its presence on the Louisiana State University campus leverages growing programs to improve both industrial outreach and diversity of our student body. The equipment adds significantly to the Louisiana Applied Polymer Technology Extension Consortium, a statewide university coalition whose primary mission is economic development in one of the poorest regions of the United States. The paucity of similar equipment in academic laboratories makes the equipment appealing to a wider audience of students, including summer interns supported by NSF-REU and a new, NIH-funded initiative targeting under-represented groups. The equipment supports a new research partnership with the University of Texas-Pan American, which trains a largely Latino student body. The equipment will play a key role in a new, interdepartmental, team-taught course, the first at Louisiana State University to address colloid science and its interface to nanoscale research and macromolecules.
