Ryan J. Murphy, Vivek M. Prabhu


The single molecule analysis of single stranded DNA and RNA translocating natural ion channels has gathered substantial attention with regards to DNA sequencing and fundamentals of the translocation process that occur in cells.  We extend this approach to synthetic polyelectrolytes using the a-hemolysin ion-channel protein pore   embedded in a lipid bilayer.  In this case, a two-barrier free energy landscape model was proposed that describes the combined molecular weight dependence and applied electric field driven translocation.  Based on this energy landscape model, we inferred a mechanism governed by the specific interactions between the charged polymer segments and the a-hemolysin protein pore, which shows that synthetic polymer translocation displays several distinguishing features when compared to the behavior of natural polyelectrolytes such as DNA or RNA.

In a second topic, we seek to answer the questions of how a polyelectrolyte adsorbs and diffuses on a patterned substrate and when confinement effects become critical as the surface pattern size is varied with respect to the polymer radius of gyration. This work will pave the way towards fluid-based directed assembly which intends to integrate functional nanostructured materials into applications on the nano to macroscopic length scale. Advanced nanofabrication techniques will be used to prepare chemically patterned surfaces to study the effect of confinement on the surface diffusion of polyelectrolytes. Quartz Crystal Microbalance-Dissipation (QCM-D) and total internal reflection fluorescence microscopy (TIRFM) will be combined to measure the adsorption concentration of polyelectrolyte molecules at the surface


Ryan J. Murphy

Mentor: Vivek M. Prabhu


NRC Postdoctoral Fellow - Polymers Division

Processing Characterization Group

National Institute of Standards and Technology

100 Bureau Drive, Building 224 MS8542

Gaithersburg, MD, 20899


Phone: 301.975.6748 -- Fax: 301.975.4924


Email: ryan.murphy@nist.gov


Sigma Xi Member: No


Category: Materials