(6bn) Measuring and Modeling Fundamental Parameters from Gas Phase Electrophoresis

Here we present a rapid and quantitative means to measure particle/cluster size distributions, from which we determine fundamental properties of molecular/particle interactions via analytical modeling. In electrospray-differential mobility analysis (ES-DMA) the balance between electrical and drag forces controls the trajectory of particles or clusters that were charged during the electrospray process. Stepping an electrode centered within an annular analysis chamber through a series of voltages guides particles or clusters with a specific size, which enter at the outside of the annulus, into a collection slit in the electrode. Collected particles then pass into a condensation particle counter where they are enumerated via light scattering to provide a size distribution. Our contributions include extending the range of samples examined by this method and providing analytical models to determine fundamental parameters. Highlights include determining the surface coverage and Kuhn length of DNA coated nanoparticles, deriving the surface charge and packing structure of gold colloids from aggregation kinetics, measuring the concentration of viral particles necessary to quantify the viral load for the biotechnology community, and performing biochemical assays. The measurements and modeling allow us to address both fundamental science questions and important applied challenges.