CONFORMATIONAL CONTRACTION AND HYDROLYSIS OF HYALURONATE IN SODIUM-HYDROXIDE SOLUTIONS

The effects of NaOH on the conformations, interactions, diffusion, and hydrolysis rates of hyaluronate (HA) were characterized in detail usi ng static light scattering (i) in the traditional ''batch'' mode (for conformations and interactions), (ii) in a time-dependent, simultaneou s multiangle mode (for the hydrolysis rates), and (iii) coupled to HPL C for preliminary characterization of distributions of hydrolysis frag ments. Strikingly, the conformations, interactions, and hydrolysis rat es all seem to be controlled by the titration of the HA hydroxyl group s by NaOH to yield -O-, which (i) destroys single strand hydrogen bond s, leading to the very rapid destiffening and contraction of the HA co il and to a large decrease in intermolecular interactions, and (ii) le ads to the slow intramolecular cleavage (hydrolysis) of glycosidic bon ds. Remarkably, the root mean square radius of gyration R(g), the seco nd virial coefficient A2, and hydrolysis rates all appear as mutually superposing titration curves which yield a pK of around 13. Interestin gly, in contrast to classical ''non-draining'' coil molecules, the hyd rodynamic radius of HA, as measured by dynamic light scattering, is in dependent of [NaOH] and the contraction of R(g).