1. Research Centre on Artificial Biopolymers, UMR CNRS 5473, and Laboratory of Amino Acids, Peptides and Proteins (LAPP), UMR CNRS 5810, Faculty of Pharmacy, University Montpellier 1, 15 Avenue Charles Flahault, BP 14491, F-34093 Montpellier Cedex 2, France, and Institute of Virology, University Louis Pasteur, INSERM U778, 3 rue Koeberlé, 67000 Strasbourg, France