Direct nanoscopic imaging: from crystallization of nanoparticles to fluctuation of membrane proteins

7 Feb
Topics in Bioengineering
Qian Chen, University of Illinois
Thursday, February 7, 2019 - 4:30pm to 5:30pm
60 Oxford Street, Room 330

We will discuss three systems whose nanoscale structure and dynamics, conventionally difficult to resolve, dictate their function. They serve as demonstration of the new opportunities at the intersection between soft materials and electron microscopy methods. The first system concerns the nucleation of growth pathways of crystals at the nanoscale, which has remained long unexplored owing to the challenge of resolving the motions of individual building blocks in a liquid medium. We address this gap by directly imaging the full transition of dispersed nanoparticles to a superlattice at the single-particle level by utilizing low-dose liquidphase transmission electron microscopy (TEM). Single-particle tracking, when combined with Monte Carlo simulation, reveals a series of unexpected crystallization pathways for different nanoparticle shapes due to inherent many-body coupling and discreteness at the nanoscale. The second system concerns an example of organic materials, polymeric films synthesized from interfacial polymerization but exhibit nanoscopic three-dimensional (3D) morphology. We image the film’s 3D morphology using electron tomography. The extensive morphometry analysis from the 3D reconstruction reveals a crumpling mechanism in the film’s morphology development. The film’s morphology also has intricate indications on their applications in water filtration, particularly solvent permeation and solute retention. The third system pushes further the boundaries of liquid-phase TEM to single biomolecules. Through extensive technological advancements, we will show first TEM movies of single membrane proteins fluctuate and rotate in their native buffer. All systems work together to achieve our common goal of deciphering fundamental rules of organization from “seeing is believing”.

Speaker Bio: 

Proessor Qian Chen is currently an Assistant Professor in the Materials Science and Engineering Department at University of Illinois at Urbana-Champaign (UIUC). She obtained her PhD from the same department with Prof. Steve Granick (2012) and did her postdoc with Prof. Paul Alivisatos at UC Berkeley under the prestigious Miller Fellowship. She joined the faculty of UIUC in 2015 and since then has received awards for the research in her group such as the Victor LaMer award in ACS (2015), Forbes 30 under 30 Science List (2016), Air Force Office of Scientific Research YIP award (2017), National Science Foundation CAREER award (2018), Sloan Research Fellow in Chemistry (2018), and the Unilever award in ACS (2018). The research in her group focuses on the broad scheme of imaging, understanding and engineering active soft matter, including systems such as nanoparticle and colloidal self-assembly, protein aggregation, advanced battery devices, and energy-efficient water filtration. 

Jennifer Vasquez