Solution Structure and Dynamics of Cartilage Aggrecan

We studied the structure and dynamics of porcine laryngeal aggrecan in solution using a range of noninvasive techniques: dynamic light scattering (DLS), small-angle neutron scattering (SANS), video particle tracking (VPT) microrheology, and diffusing wave spectroscopy (DWS). The data are analyzed within the framework of a combined static and dynamic scaling model, and evidence is found for reptation of the comb backbones with unentangled side-chain dynamics. Small-angle neutron scattering indicated standard polyelectrolyte scaling of the mesh size (ξ) with concentration (c) in semidilute solutions for the whole aggrecan aggregate, ξ = Ac -0.47±0.04, with the prefactor (A) implying there is on average 60 nm between the aggrecan subunits along the backbone. VPT demonstrated large exponents for the power law dependence of the intrinsic viscosity (η) on the polymer concentration in the semidilute concentration regime, η ∼ c α; with α equal to 2.04 ± 0.06 and 1.95 ± 0.08 for the assembled and disassembled aggrecan aggregates, respectively. DWS at high frequencies (104−105 Hz) gave evidence for internal Rouse modes of the aggrecan monomers, independent of the degree of self-assembly of the molecules.