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 Cecile Fradin

Cécile Fradin

Assistant Professor

Department of Physics and Astronomy 
McMaster University
1280 Main St W
Hamilton, ON, L8S 4M1

Joint appointment: Dept. of Biochemistry and Biomedical Sciences

Office:  ABB-346
Lab: ABB-330

Phone:  (905) 525-9140 x23181 (office),  x26126 (lab)
Fax:      (905) 546-1252
E-mail: fradin@physics.mcmaster.ca
Research Area:  Molecular Biophysics


Short Biography:

I received my university degree in Physics from the Université Pierre et Marie Curie in Paris, and obtained a Ph.D. in Soft Condensed Matter working with Dr. Jean Daillant at the Commissariat à l'Energie Atomique (CEA) (Saclay, France). I then redirected the focus of my research to Biophysics during my post-doctorate in the group of Dr. Michael Elbaum at the Weizmann Institute of Science (Rehovot, Israel). I started my own group at McMaster University in November 2001, on a joint position between the Physics and Astronomy department and the Biochemistry and Biomedical Sciences department.

General Research Interests:

I am interested in studying the dynamics of single molecules inside biological systems using optical tools. Dynamics is essential to the survival of the cell, which is a biological unit in permanent evolution, and which has to be able to process and react to information. Dynamical processes inside the cell happen on a very wide range of length and time-scales, and are governed by complex and intricate rules and mechanisms. At the scale of the molecule, they are of interest for the physicist as well as for the biologist, since they involve basic transformation of chemical or thermal energy into mechanical energy. In order to unravel their exact mechanisms, in vivo quantitative measurements at the single molecule level are required, which recent developments in the domain of fluorescence techniques, single molecule detection, and recombinant protein technology now offers the possibility to do.

Specific Research Directions:

We use several different experimental techniques, among which fluorescence correlation spectroscopy and single particle tracking, to study single molecule dynamics.

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 proteins.

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.

Keywords:

Cellular dynamics, single molecule dynamics, diffusion, macromolecular crowding, nuclear transport, membrane fluctuations, conformational changes, fluorescence, fluorescence correlation spectroscopy.


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