Friday, March 5, 2010
Reprogramming Bacteria with Small Molecules and RNA
Simple organisms, such as the bacterium E. coli., carry out a wide variety of complex chemical tasks. E. coli cells synthesize complex molecules, communicate with one another, move in response to changing conditions, and replicate themselves every 20 minutes. The programs that control these behaviors are encoded in a genome so small that its entire information content can be stored on a 3.5-inch floppy disk with room to spare.
In this talk, I will present our recent efforts to reprogram E. coli to sense new small molecules and to respond to them with predictable behaviors. Specifically, I will describe our efforts to create synthetic riboswitches, which are designer RNA sequences that control gene expression in a ligand-dependent fashion without the need for proteins. I will show how synthetic riboswitches can be used to engineer bacteria to have a variety of functions, including the ability to seek and destroy small molecules. Finally, I will show how synthetic riboswitches are useful tools for studying the genetics of a variety of different bacteria.
Journal Club Meets This Week
Journal Club meets this Thursday at noon in Mudd 171 to discuss a paper relating to this week’s seminar. Go to the following for information about what to read beforehand: http://apps.carleton.edu/curricular/chem/events/?category=171005&no_search=1.
Physics Comps Talk
Molecular Electronics: Exploring the Limits of Small
March 10, 2010 (Last day of classes)
Smaller is better, we’ve been told, but in the age of Intel’s 32 nm transistor it is increasingly challenging to scale down electronic circuitry because quantum mechanics begins to play a role. The use of individual molecules as circuit elements (hence the name molecular electronics) provides an opportunity for scientists to harness quantum mechanics and use it to control conduction at the nanoscale. Both the chemical structure of the molecule used and its geometry within the junction can dramatically affect the conduction properties of a molecular device, which means that molecules can act not only as wires but also as diodes, switches, and even single-electron transistors. Molecules offer unique properties not available to silicon nanostructures, which allows for totally new switching mechanisms in circuits (e.g. change of conformation upon binding an analyte). Molecular devices will be discussed in the context of quantum mechanical charge transport mechanisms, including tunneling and thermally activated hopping, and the talk will conclude with a discussion of exciting new molecular devices.