RUI:Test and Measurement Strategies for the Development of Biological Nanovalves

With support from the Chemical Measurement and Imaging Program in the Division of Chemistry and co-funding from the Interfacial Engineering Program in the Division of Chemical, Bioengineering, Environmental, and Transport Systems, Dr. Daniel Burden, Dr. Lisa Keranen-Burden, and their group in the Chemistry Department at Wheaton College are developing a new set of laser-based tools that combine ultrasensitive microscopy with electrical measurements and protein engineering to monitor the movement of charged species through nanopores wherein protein toxins are used as nanovalves.

Their studies seek answers to questions such as what molecular sizes, shapes, and charge states are allowed to flow through the nanoscale valve interior, and what chemical modifications to the nanovalve are necessary to make it switchable on demand from the fully-on state to the fully-off state. The insights gained will likely be useful for a broad range of applications, including selective access to the interior of cells to fight infections, nanoscale separations, and chemical sensors.

The research team is also working to enhance the size and diversity of the pool of qualified candidates for advanced STEM degrees by investing in undergraduate research. Elements of the research are integrated into the undergraduate curriculum, summer research opportunities, and public outreach activities in the surrounding community.

Measurement methods in ion-channel electrophysiology have traditionally been used to monitor the movement of charged species through nanopores. However, many translation events are electrically silent and cannot be detected. Furthermore, an understanding of the sizes, shapes, charge states, and flow rates of species that can be transported (or blocked), as well as their relationship to nanovalve gating mechanisms, is critically important for developing future applications within the field.

The Burden group is investigating whether the alpha-HL toxin protein can be chemically modified to reversibly halt or permit molecular flow on demand. They also hypothesize that the size and rate of transported molecules will shift markedly upon triggered valve closure. They are developing measurement tools based on wide-field fluorescence microscopy, single-molecule confocal microscopy, and ion-channel electrophysiology to test a range of nanovalve constructs, with the ultimate aim of monitoring molecular transport across lipid membranes in a chip-based bilayer apparatus in real time.

The PIs are working with multiple undergraduate students, reaching out particularly to first-generation college-bound African-American or Latino students from the Chicago area. The PIs are also actively working with outreach publishers to improve communicating research outcomes to the public.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.