2023 Seminars
Spring 2023
These meetings occur on Mondays from 4:00pm to 5:00pm
Virtual Zoom Seminars (unless otherwise indicated)
Monday 4:00pm
Virtual Zoom
(poster)
Host:
Monday 4:00pm
Zoom Link
(poster)
Dr. Gaoyang Bridget Fan Altos Labs
"Pattern formation and bi-stability in a synthetic intercellular genetic toggle"
Differentiation within multicellular organisms is a complex process that helps to establish spatial patterning and tissue formation within the body. Often, the differentiation of cells is governed by morphogens and intercellular signaling molecules that guide the fate of each cell, frequently using toggle-like regulatory components. Here, we couple a synthetic co-repressive toggle switch with intercellular signaling pathways to create a “quorum-sensing toggle.” We show that this circuit not only exhibits population-wide bi-stability in a well-mixed liquid environment, but also generates patterns of differentiation in colonies grown on agar containing an externally supplied morphogen. We develop a mechanistic mathematical model of the system, to explain how degradation, diffusion, and sequestration of the signaling molecules and inducers determine the observed patterns.
Host: Prof. Uwe Tauber
May 22
Monday 4:00pm
Zoom Link: https://virginiatech.zoom.us/j/84066367405
(poster)
Prof. Alastair Rucklidge
University of Leeds, Germany
"Cycling behavior and spatial structure in a hetero-clinic network model of Rock-Paper-Scissors-Spock-Lizard
The well-known game of Rock-Paper-Scissors can be used as a simple model of competition between three species. When modeled in continuous time using ordinary differential equations, the resulting system contains a hetero-clinic cycle between the three equilibrium solutions that represent the existence of only a single species. The game can be extended in asymmetric fashion by the addition of two further strategies (`Spock' and `Lizard'):now each strategy is dominant over two of the other four strategies, and is dominated by the remaining two. The ODE model contains coupled hetero-clinic cycles forming a hetero-clinic network. We develop a technique, based on the concept of fragmentary asymptotic stability, to understand the stability of arbitrarily long periodic sequences of visits made to the neighborhoods of the equilibrium. The regions of stability form a complicated pattern in parameter space. By adding spatial diffusion, we extend to a partial differential equation model and investigate the spatiotemporal evolution of these periodic itineraries.
Host: Prof. Uwe Tauber
Fall 2023
These meetings occur on Mondays from 4:00pm to 5:00pm
Virtual Zoom Seminars (unless otherwise indicated)
Monday 4:00pm
Virtual
(poster)
Host:
Monday 4:00pm
Zoom Link
(poster)
Prof. John M. Franck Syracuse University
"Confinement and Interfaces Make Water Weird: Observations with Ultra-Sensitive Magnetic Resonance Cross-Relaxation"
Many of the problems that we face today – such as the ability to understand why proteins form the structures that they do, or to understand how to design a drug or material with specific properties without first having to screen large numbers of candidate compounds – could be solved if only we had a handle on the properties of water at the interfaces of macromolecules. Magnetic resonance provides a means of characterizing the structure of liquid water, despite its dynamic nature, with a dual-resonant NMR-ESR tool called ODNP (Overhauser Dynamic Nuclear Polarization). In practice, building up such a measurement requires a multifaceted research program that in part tests realistic applications, in part delves into the interesting physics driving the measurement, and in part performs controlled analyses of carefully designed chemical systems that reveal the properties of interfacial and confined water. We address these aspects, respectively, through a clear model for the physics of the ODNP measurement1 and a powerful tool for optimizing the resulting signal2; measurements of hydration water on the surface of protein systems3; and studies of reverse micelles that grant an understanding of how confinement in isolated chambers or pockets fundamentally manipulates the nature of water4,5.Taken together, this work will enable routine measurements that probe how the transformation of interfacial water molecules into bulk solvent molecules, and vice versa contributes to the thermodynamic cycle driving biochemical and biomimetic materials systems.
Host: Vinh Nguyen