Giving to CREOL CREOL, The College of Optics & Photonics

Biophotonics Faculty Candidate Seminar: "Super-resolution imaging and tracking of synaptic receptors in live neurons" by Sang Hak Lee

Thursday, February 8, 2018 11:00 AM to 12:00 PM
CREOL Room 103

Sang Hak Lee
Department of Physics and the Center for Physics of Living Cells (CPLC)
University of Illinois at Urbana-Champaign


In our brain, there are about 100 billion neuronal cells, making over 100 trillion connections with
other nerves, sending and receiving electric impulses. Memories are formed –or forgotten—when
these connections are reinforced, or degraded, over time. We wish to understand how this happens.
Two of the most important receptors in these connections are called AMPA and NMDA receptors. They are turned on when glutamate, a small amino acid, is released from one nerve, diffuses across a tiny synaptic cleft (just 20-40 nm across), and causes these two receptors to be turned on. Repetition of these events tend to make the connections stronger by increasing the amount of AMPA receptors, which is a memory forming; forgetting is when the AMPA receptors go away. I therefore wish to understand their dynamics and the underlying mechanism that creates or deletes memories. I have accurately imaged the dynamics of these receptors using super-resolution optical (fluorescent) microscopy with 10-20 nm accuracy, a factor of 10x better than conventional optical microscopy, and single molecular tracking with 50 msec resolution. I have used small quantum dots (sQDs) to make the AMPA (and NMDA) receptors light up. sQDs are approximately 10 nm in diameter, compared to previous ones that are ~20 nm in diameter. With these sQDs, I find that AMPA (and NMDA) receptors are quite stable within the synaptic domain, lasting at least 15 minutes, diffusing in a confined area, and spend hardly anytime outside of it. This is in direct contrast to previous claims where researchers used large quantum dots and found the receptors were highly diffusive. This mistaken impression has misled the field. We can now begin to understand the process of memory formation using super-resolution and small quantum dots.


Sang Hak Lee is a Postdoctoral Research Fellow in Physics and the Center for Physics in Living Cells (CPLC) at the University of Illinois at Urbana-Champaign. He received his PhD in Chemistry from Seoul National University in 2009. His research interest include Neuronal glutamate receptor dynamics (AMPA receptor, NMDA receptors, Kainate receptors); Interpretation Neuronal diseases (Alzheimer’s disease, schizophrenia) using Chemistry; The role of small molecules to make protein clusters or DNA-protein complexes; Cell to cell communication such as cell signaling, immunization; Development state-of-art optical imaging methods; Development state-of-art optical tool to diagnose brain diseases.

For additional information:

Peter J. Delfyett

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