Beckman Postdoc Fellows Checco and Yoon to Present May 2 at Director's Seminar

Beckman Institute Postdoctoral Fellows James Checco and Si On Yoon will present their research at noon, May 2, at the final Director’s Seminar of the spring semester. Checco will talk about “Exploring the Signaling of D-amino Acid-containing Neuropeptides,” and Yoon will discuss “When is Declarative Memory Necessary for Audience Design? Evidence from Amnesia.” The lecture is open to the public, and lunch is provided. No registration is required.

"Exploring the Signaling of D-amino Acid-containing Neuropeptides"

James Checco, Beckman Institute Postdoctoral Fellow

James Checco will speak at the next Beckman Institute Director's Seminar at noon, Thursday, May 2, in Room 1005.


Neuropeptides are cell-to-cell signaling molecules which facilitate communication among neurons within the central nervous system. Although neuropeptides translated by the ribosome contain exclusively L-amino acid residues, neuropeptides in several animals undergo an unusual post-translational modification: the enzyme-catalyzed isomerization of an amino acid residue from the L-stereoisomer to the D-stereoisomer. The resulting D-amino acid-containing peptide (DAACP) often displays higher biological activity and stability than the all-L-residue analogue. However, because L- to D-residue isomerization is undetectable by most peptide characterization techniques, DAACPs are difficult to identify and little is known about how DAACPs engage their receptors and mediate physiological functions. Here, we study the signaling DAACPs in Aplysia californica, a well-studied model organism for learning and memory. Ultimately, these studies advance our understanding of the role of L- to D-residue isomerization, a functionally critical yet understudied post-translational modification, in neuropeptide signaling.

Speaker Biography

James W. Checco earned a Ph.D. in chemistry from the University of Wisconsin-Madison in 2015, where he worked with Professor Samuel Gellman to design non-natural peptides to target protein-protein interactions. He came to the University of Illinois in 2015 to pursue postdoctoral research with Professor Jonathan Sweedler, joining the Beckman Institute as a Beckman Institute Postdoctoral Fellow in July 2016. Checco’s research in the Sweedler lab focuses on understanding the occurrence and functions of neuropeptides with rare post-translational modifications. This fall, he will join the University of Nebraska-Lincoln as an assistant professor of chemistry, where his research will focus on understanding the molecular-level details underlying cell-cell signaling of neuropeptides and peptide hormones.

"When is Declarative Memory Necessary for Audience Design? Evidence from Amnesia"

Si On Yoon, Beckman Institute Postdoctoral Fellow

Si On Yoon will speak at the next Beckman Institute Director's Seminar at noon, Thursday, May 2, in Room 1005.


Communicating with others is one of the most fundamental social activities of everyday life. Even though communication plays an undeniably important role in our lives, the mechanisms of language processing used in conversation are largely unexplored due to the difficulties in examining natural conversational language with traditional psycholinguistic approaches. In a newly developed experimental paradigm to study conversation in the lab, I have examined the nature of the memory representations that are built and used during natural communication. I test individuals with hippocampal amnesia and severe memory impairment, as well as healthy older adults, to examine the role of episodic memory while communicating. In three experiments, the results show that individuals with severe declarative memory impairment flexibly adjust expressions depending on the current addressee’s knowledge state, like healthy adults. This sparing of audience design was juxtaposed against an inability to explicitly recall who they had shared the past experience with. While thinking about past episodes can certainly support reasoning about common ground in healthy individuals, here I show that using common ground does not require episodic memory. These findings are consistent with the multiple-memory systems view of the role of common ground in conversation.

Speaker Biography

Si On Yoon earned a Ph.D. in psychology from the University of Illinois at Urbana-Champaign in 2016. That same year, she became a Beckman Institute Postdoctoral Fellow. Her research interests take a cognitive science approach to the study of complex language processes. She examines how people use social-pragmatic information in conversation, such as how speakers design what they say depending on their partner’s knowledge, and how previously-discussed information influences language production and comprehension in the moment. Yoon is also interested in how this ability to use social-pragmatic cues during language processing develops and how this ability varies across populations (e.g., children, older adults and individuals with severe memory impairment). A theme throughout her work is understanding the cognitive mechanisms of natural conversation and the role of the memory representations that support natural language use.