Section: New Results

Atomic force microscope

Participants : Olivier Gibaru, Wilfrid Perruquetti, Dayan Liu, Stéphane Thiery.

The atomic force microscope (AFM) is unique in its capability to capture high-resolution images of biological samples. This capability will become more valuable to biological sciences if AFM additionally acquires an ability of high-speed imaging, because "direct and real-time visualization” is a straightforward and powerful means to understand biomolecular processes. With conventional AFMs, it takes more than a minute to capture an image, while biomolecular processes generally occur on a millisecond timescale or less. In order to fill this large gap, various efforts have been carried out in the past decade. Our objective is to apply the ALIEN methods so as to break the limitations and lead to the development of a truly useful high-speed AFM for virology with very good nanometer resolution.

We already got significant advances. The Coksakie virus B4 in its structural form at 37^oC has been imaged for the first time by atomic force microscopy (AFM). These virus particles were spread on glass substrates. They are roughly spherical, reasonably uniform, and have diameters of about 30 nanometers. This work which is managed by Olivier GIBARU, is done in collaboration with Didier HOBER director of the virology team of CHRU Lille (Univ. Lille 2) and Sébastien DUCOURTIEUX from the LNE. The research activity of the virology team concerns the involvement of the enterovirus in the disease of diabetes of kind one. The measure by AFM will allow us to improve the knowledge of enterovirus (30 nm) in particular their interactions with antibodies enabling the infection of human cells through an interaction (with a piece) of a protein called VP4 of the virus capsid. In addition, it will be possible to visualize by AFM any viruses attached to various media for dealing with the nosocomial diseases.

Recently, we applied the non asymptotic algebraic methods developed in ALIEN to improve the measurement accuracy and the dynamic of AFM [58] . This improvement allows us to improve the measurements in liquid of biological structures such as the virus capsid. This work was done in collaboration with the French National Laboratory (LNE) located in Trappes. Indeed, this laboratory has an AFM with an open electronic system which allows us to implement our methods and our algorithms. The results are very encouraging.