Integrated Calendar

The complete characterization at the atomic level of large amplitude conformational changes of macromolecules, or of their complexes, is needed in order to determine those that might be involved in their function. This remains a challenging task for large systems in the field of molecular simulation. The exclusive use of molecular dynamics for such characterization might not be necessarily the best choice for many reasons. Indeed, in order to characterize a large variety of collective motions, extremely lengthy simulations are required, and moreover some motions may never occur due to the complexity of the system and high energy barriers. A convenient approach to circumvent this difficulty is to rely on the topology of the potential energy surface that gives useful information on the possible low energy pathways for the conformational changes to occur. I will present how normal mode analysis, which takes advantage of the curvature of the energy surface near a given conformation, may be used to identify the important large scale motions that might influence function, and how these motions may be explored by a combined use of normal modes with other simulation techniques such as energy minimization or molecular dynamics simulations. I will present a number of applications to illustrate the techniques that we have developed in our laboratory to explain how collective motions are involved in the formation of cavities and tunnels in some proteins which are important for their activity. Such applications also open new areas for the discovery or design of inhibitors for a given protein exhibiting global conformational flexibility.

The Local Group galaxy M32 is a compact elliptical galaxy, satellite of M31. Although a low-luminosity galaxy, M32 is the nearest system with structural properties reminiscent of giant ellipticals. Given its proximity, M32 provides a unique window on the stellar composition of elliptical galaxies since it can be studied by both its integrated spectrum and the photometry of its resolved stars. To date, however, there has not been a consistent comparison between predictions from the spectroscopic
analysis of its integrated light and its resolved stellar content. Moreover, the SFH of M32 is still a matter of debate. In this talk, I will focus on the resolved stellar populations of M32 at 2 arcmin from its center. Very high resolution HST observations of two fields near M32 were used to construct and analyze deep color-magnitude diagrams (CMDs). These CMDs reveal the different stellar populations present in M32 and allow us to extract information about the stellar ages and
metallicities distributions in this galaxy, from both qualitative and
quantitative analyses. I will also show the results from the study of RR
Lyrae variable stars in the same fields. I will discuss the formation of
M32 based on our results and conclude by discussing some follow up studies
based on this work.

In the past few decades, large amount of knowledge about the solar corona and solar wind has been gathered by both in-situ and remote measurements all over the solar system. However, this knowledge is not fully considered in stellar astrophysics. In particular, mass loss of stars to their stellar winds are traditionally related to their level of activity and their X-ray flux. In the talk, I will overview the known properties of the solar wind and will show how the solar mass flux and the solar X-ray flux do not seem to correlate at all. I will also discuss the possible reason for this finding.