Physics Special Colloquium, December 2, 2004

Mesoscopic Phenomena in Biology: From Chromosomes to Bacteria Populations

Michael Guy Poirier

Department of Biochemistry, Molecular Biology and Cell Biology, Northwestern University

Over the past ten years there has been exciting advances in biological physics by measuring at the single molecule level. However, within biology, objects made of many molecules such as chromosomes and cells can also be thought of as individual units. Measurements at the single unit level can provide additional information to that of ensemble measurements. I will present experiments of two different biological systems that probe at this mesoscopic scale.

The first system, metaphase chromosome structure, was studied by combined micromechanical force measurements and biochemical modifications. I will discuss how we measure elastic properties of single metaphase chromosomes, how they change in response to DNA cutting enzymes and their ramifications on models of metaphase chromosome structure.

The second experimental system, clonal populations of bacteria, is being investigated by measuring the variation in the number of plasmids per cell. These measurements should help in understanding how DNA replication and partioning are regulated. The approach is to combine techniques from molecular biology, microfluidics and fluorescent microscopy. I will describe how we plan to measure variations in plasmid copy number, our initial experimental results and on going improvements to the experimental design.

1:30 p.m., Smith Laboratory, Room 1094

Refreshments served in Smith 1094 at 1:00 p.m.