Hyaluronan (HA), a negatively charged linear polysaccharide of very regular structure, has very important physiological roles in living organism such as the maintenance of the viscoelasticity of corporal fluids (in synovial liquids in the joints, eye vitreous humor). It participates to tissue repair, tumor development or inflammation process. The effect of the HA structure (at the mesoscale level) on its biological properties is a question largely open nowadays. We are investigating HA / proteins complexes for few years by SANS which is a powerful tool to characterize the structure. With lysozyme, a globular protein negatively charged protein, SANS scattering has demonstrated the presence of a rod-like necklace of proteins for given HA / lysozyme ratios, organization that has never been observed until now in other polyelectrolyte / protein complexes. The goal of this proposal is to investigate the structure of HA insidenthe complexes by using deuterated HA, recently available, in 43% H2O / 57 % / D2O, solvent that will matches the proteins.