Evaluation of Radius of Gyration and Intrinsic Viscosity Molar Mass Dependence and Stiffness of Hyaluronan

Abstract

Nine hyaluronan (HA) samples were fractionated by size-exclusion chromatography, and molar mass (M), radius of gyration (R_g), and intrinsic viscosity ([η]) were measured in 0.15 M NaCl at 37 °C by on-line multiangle light scattering and viscometer detectors. Using such method, we investigated the R_g and [η] molar mass dependence for HA over a very wide range of molar masses: M ranging from 4 × 10⁴ to 5.5 × 10⁶ g/mol. The R_g and the [η] molar mass dependence found for HA showed a meaningful difference. The R_g = f(M) power law was substantially linear in the whole range of molar masses explored with a constant slope of 0.6. In contrast, the [η] = f(M) power law (Mark−Houwink−Sakurada plot) showed a marked curve shape, and a linear regression over the whole range of molar masses does not make sense. Also the persistence length (stiffness) for HA was estimated. The persistence length derived by using both the Odijk's model (7.5 nm from R_g vs M data) and the Bohdanecky's plot (6.8 nm from [η] vs M data) were quite similar. These persistence length values are congruent with a semistiff conformation of HA macromolecules.