Dependence of polyelectrolyte apparent persistence lengths, viscosity, and diffusion on ionic strength and linear charge density

Influence of Chain Stiffness on the Interaction of Polyelectrolytes with Oppositely Charged Micelles and Proteins

“…While this would correspond to 25 mol % AMPS, results reported elsewhere suggest that high-conversion random ionic-nonionic copolymers display, in their binding to oppositely charged colloids, effective charge densities slightly larger than their average compositions would indicate, because the onset of complexation is governed by residue sequences enriched in the ionic monomer residue; 16 for this reason we employ a 20% AMPS copolymer. The ionic strength dependence of the persistence length of the copolymer (AMPS 17 /AAm 83 ) has been reported by Reed et al, 25 and its bare persistence length l p°f alls within the range of values reported for the two corresponding homopolymers, i.e., between 2 and 3 nm. For hyaluronic acid (HA), values for l p°r anging from 4 to 9 nm have been reported; [26][27][28][29][30] here we use the values closer to 4 nm of Hayashi et al, 27,28 who have argued that the larger l p°v alues reported elsewhere arise from a significant effect of the excluded volume on the z-average radius of gyration.…”

“…32 To further evaluate the effects of chain stiffness and charge density, the results for HA-SA and Hp-SA were compared with the binding of SA to two synthetic polyelectrolytes, copolymers AMPS 25 /AAm 75 and AMPS 80 /AAm 20 , the first of which has a mean charge density equal to that of HA, while the second has an average charge density similar to that of Hp. Both bovine serum albumin (for AMPS 25 /AAm 75 , AMPS 80 /AAm 20 , Hp, and HA interaction) and human serum albumin (for HA interaction) were used for this study, and the results are represented without differentiation since both proteins revealed the same results regarding critical binding conditions. 46 Since protein charges are pH dependent, titrations were carried out by varying pH and observing the turbidity change in order to identify a critical pH at which complex formation begins.…”

“…It should also be noted that values of pH c below 5 (i.e., Z c < 0) correspond to protonation of the carboxylate groups of HA, complicating the interpretation of the phase boundary. 25 /AAm 75 can be expected to facilitate polymer configurations that will reduce the repulsive effect arising from negatively charged protein domains and favor the alignments around the positively charged protein domains. 44 The stiffness of HA corresponds to a restriction of chain movements, so that the bound configuration may not readily avoid negative domains, and therefore binding cannot take place when the net charge is strongly negative.…”

“…The interaction of HA and AMPS 25 / AAm 75 with serum albumin shows a more striking binding affinity for the more flexible chain due to its ability to adopt configurations that bind to a local positive "patch", while minimizing the repulsive effect arising from the negatively charged domains of the protein. The nature of the polyelectrolyte charge distribution may also have a significant effect on interactions with proteins as inferred from differences among Hp, AMPS 25 /AAm 75 , and AMPS 80 /AAm 20 .…”

The analysis of intermolecular interactions in concentrated hyaluronan solutions suggest no evidence for chain–chain association

“…This is in contrast to results from dynamic lightscattering studies, but consistent with changes reported in the R g and intrinsic viscosity of HA [10,27]. Discrepancies may be due to the presence of non-translational diffusion modes detected by dynamic light scattering [28].…”