Department of Physics and Astronomy
Joint appointment: Dept.
of Biochemistry and Biomedical Sciences
Phone: (905) 525-9140 x23181 (office),
Diffusion of macromolecules in crowded media: A major effort
in our group has been to chracterize the diffusion of macromolecules in
crowded media. This is a prerequisite to understanding diffusive
motions in cells as the cellular environment is very heavily crowded.
We have studied the influence of the presence of soft biological
membranes and high concentrations of cosolute on the diffusion of
Nuclear transport: The transport of proteins and nucleic
acids across the nuclear membrane is a fundamental process that allows
in particular to maintain the proper environment for the preservation
and processing of the cell genetic material. Nuclear transport is
selective and directed, and involves translocation of the
macromolecules across a large protein assembly spanning the membrane,
the nuclear pore complex. We are interested in the translocation
mechanism, and in particular in the characteristic time associated with
the passage of a single macromolecule in the nuclear pore complex.
Interaction of proteins with membranes: Different proteins, such as
the diphteria toxin and bacterial colicins, have the ability to oligomerize,
insert into lipid membranes and form pores large enough to allow the diffusion
of other macromolecules through the membrane. We are interested in the behavior
of one such protein, Bax, which is involved in the permeabilization of the mitochondrial
membrane at the onset of apoptosis. This project is carried out in collaboration
with Dr David Andrews (Sunnybrook Research Institute, Toronto).
Membrane fluctuations: The thermal fluctuations of
biological membranes are influenced by a number of factors, among which
their compositon and their interaction with the cell cytoskeleton. We
use the contrast created by the the presence of fluorophores on one
side of the membrane only to detect these fluctuations in situ and
study cellular elasticity.
Conformational changes of macromolecules: Fluorescence correlation spectroscopy used in conjunction with either FRET or fluorescence quenching allows detecting and characterizing conformational changes of proteins and nucleic acids. We are using this technique to study the fast conformational changes of small single-stranded DNA molecules.
To learn more about our research projects and see some movies of
cellular dynamics, visit our group website.