Bulletin of the American Physical Society
77th Annual Meeting of the Southeastern Section of the APS
Volume 55, Number 10
Wednesday–Saturday, October 20–23, 2010; Baton Rouge, Louisiana
Session CA: Dynamics in Living Cells |
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Chair: Jennifer Curtis, Georgia Institute of Technology Room: Nicholson Hall 119 |
Thursday, October 21, 2010 10:45AM - 11:15AM |
CA.00001: Observing the conformation of individual SNARE proteins inside live cells Invited Speaker: Protein conformational dynamics are directly linked to function in many instances. Within living cells, protein dynamics are rarely synchronized so observing ensemble-averaged behaviors can hide details of signaling pathways. Here we present an approach using single molecule fluorescence resonance energy transfer (FRET) to observe the conformation of individual SNARE proteins as they fold to enter the SNARE complex in living cells. Proteins were recombinantly expressed, labeled with small-molecule fluorescent dyes and microinjected for in vivo imaging and tracking using total internal reflection microscopy. Observing single molecules avoids the difficulties of averaging over unsynchronized ensembles. Our approach is easily generalized to a wide variety of proteins in many cellular signaling pathways. [Preview Abstract] |
Thursday, October 21, 2010 11:15AM - 11:45AM |
CA.00002: Amyloid Nucleation and Assembly Dynamics Invited Speaker: The nucleation and growth mechanisms in amyloid forming materials are of high interest due to their importance in human diseases and also due to their potential applications as functional nano-materials. While much is known about the secondary structure of amyloids materials, the nucleation mechanism and self-assembly processes remain poorly understood. We have recently identified unstructured intermediates play a critical role in early nucleation and assembly of amyloid nanotubes in model peptide systems, and resolved that initial assembly proceeds via monomer addition to the ends of elongating tubes. We will discuss our current understanding of these assembly pathways, and discuss recent measurements highlighting dynamic structural evolution as nanostructures mature following initial assembly. [Preview Abstract] |
Thursday, October 21, 2010 11:45AM - 12:15PM |
CA.00003: Noise and heterogeneity in bacterial communication Invited Speaker: Many bacterial species engage in a sophisticated chemical communication behavior known as quorum sensing: Individual cells release small diffusible molecules into their environment while simultaneously detecting the local concentration of these molecules. Important collective behaviors of the bacterial population are triggered once the signal concentration accumulates to a certain level. Although quorum sensing is widespread in microbiology, the physical environment of bacteria is often very heterogeneous and diffusion may be inefficient. Meanwhile the genetic circuitry that generates and detects the chemical signal is microscopic and subject to stochasticity. This raises interesting physical questions about how much information is actually carried by these chemical signals, and what an individual cell can learn about its environment through this mechanism. I will present a general introduction to quorum sensing with emphasis on our experimental studies of the role of noise and microenvironment on this phenomenon. [Preview Abstract] |
Thursday, October 21, 2010 12:15PM - 12:45PM |
CA.00004: Quantifying the Effect of DNA Packaging on Gene Expression Level Invited Speaker: Gene expression, the process by which the genetic code comes alive in the form of proteins, is one of the most important biological processes in living cells, and begins when transcription factors bind to specific DNA sequences in the promoter region upstream of a gene. The relationship between gene expression output and transcription factor input which is termed the gene regulation function is specific to each promoter, and predicting this gene regulation function from the locations of transcription factor binding sites is one of the challenges in biology. In eukaryotic organisms (for example, animals, plants, fungi etc), DNA is highly compacted into nucleosomes, 147-bp segments of DNA tightly wrapped around histone protein core, and therefore, the accessibility of transcription factor binding sites depends on their locations with respect to nucleosomes - sites inside nucleosomes are less accessible than those outside nucleosomes. To understand how transcription factor binding sites contribute to gene expression in a quantitative manner, we obtain gene regulation functions of promoters with various configurations of transcription factor binding sites by using fluorescent protein reporters to measure transcription factor input and gene expression output in single yeast cells. In this talk, I will show that the affinity of a transcription factor binding site inside and outside the nucleosome controls different aspects of the gene regulation function, and explain this finding based on a mass-action kinetic model that includes competition between nucleosomes and transcription factors. [Preview Abstract] |
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