Polyelectrolyte conformation, interactions and hydrodynamics show a marked dependence on the ionic strength (C$\sb{\rm s}$) of the medium, the concentration (C$\sb{\rm p}$) of the polymer itself and their charge density ($\xi$). The apparent electrostatic persistence length obtained from static light scattering varied approximately as the inverse square root of C$\sb{\rm s}$ for highly pure, high molecular weight hyaluronate (HA) as well as for variably ionized acrylamide/sodium acrylate copolymers (NaPAA), and linearly with $\xi$. The experimental values of persistence length and second virial coefficient (A$\sb2$) are compared to predictions from theories based on the Debye-Huckel approximation for the Poisson-Boltzmann equation and on excluded-volume. Although the mean square radius of gyration ($\rm\langle S\sp2\rangle$) depended strongly on C$\sb{\rm s}$. $\rm\langle S\sp2\rangle$ decreasing with increasing C$\sb{\rm s}$ for both HA and NaPAA indicating clear evidence of polyion expansion, dynamic light scattering values of the translational diffusion coefficient (D) remains constant when extrapolated to infinite polymer concentration for both the polymers. The behavior of D is compared to predictions from coupled mode theory in the linear limit. The effects of NaOH on the conformations, interactions, diffusion and hydrolysis rates of HA are characterized in detail using static, dynamic and time-dependent light scattering supplemented by size exclusion chromatography (SEC). For the HA $\rm\langle S\sp2\rangle,\ A\sb2$ and the hydrolysis rates all resemble superposing titration curves, while the D remains independent of both the concentration of NaOH, and the contraction of $\rm\langle S\sp2\rangle$. The indication is that the interactions, conformations and the hydrolysis rates are all controlled by the titration of the HA hydroxyl groups by the NaOH to yield -O$\sp-$, which (i) destroys single strand hydrogen bonds, leading to de-stiffening and contraction of the HA coil and a large decrease in intermolecular interaction, and (ii) slowly depolymerizes HA. The experimental results of HA depolymerization is compared to predictions from the theory of random scission. PGM depolymerization is carried out with (i) NaOH, (ii) hyaluronidase, (iii) HCl. These agents degraded the polymer in different ways. NaOH apparently stripped off the GAG chains from the protein backbone. Hyaluronidase seemed to randomly cleave the GAG sidechains, while HCl both stripped the GAG sidechains and randomly cleaved the protein backbone. Time dependent static light scattering of each degradation mechanism traced out its own characteristic signature of reciprocal scattered intensity versus time, models for which are presented. This technique allows degradation mechanisms, associated rates and percentage of material in the backbone and sidechains to be determined. The presence and removability of the 'extraordinary' diffusional phase (EP) at low ionic strength are investigated exhaustively for HA, NaPAA, polystyrene sulfonate, poly(L)lysine, heparin and chondroitin sulfate. The EP is found to be always removable by filtration through a sufficiently small pore-size membrane / acase@tulane.edu
| Identifer | oai:union.ndltd.org:TULANE/oai:http://digitallibrary.tulane.edu/:tulane_25009 |
| Date | January 1994 |
| Contributors | Ghosh, Snehasish (Author), Reed, Wayne F (Thesis advisor) |
| Publisher | Tulane University |
| Source Sets | Tulane University |
| Language | English |
| Detected Language | English |
| Rights | Access requires a license to the Dissertations and Theses (ProQuest) database., Copyright is in accordance with U.S. Copyright law |
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