Association between Protein Particles and Long Amphiphilic Polymers:  Effect of the Polymer Hydrophobicity on Binding Isotherms

Abstract

Association isotherms of bovine serum albumin (BSA) onto hydrophobically modified polyacrylates (HMPA) in aqueous solution were determined by frontal analysis continuous capillary electrophoresis experiments. A set of alkyl-grafted polyacrylates was studied by varying the degree of grafting and the length of the dangling alkyl groups, keeping constant the molar mass and the polydispersity. Binding isotherms indicate that both the concentration of free BSA and the hydrophobicity of the HMPA control the association, which is anti-cooperative. In the presence of a large excess of protein, the number of bound proteins per HMPA chain was found to increase linearly with an increase in the percentage of the dangling groups along the backbone. Although HMPA modified with dodecyl groups required higher protein concentrations to reach the saturation than those with octadecyl grafts, the results suggest that the saturation composition of the complexes correspond to three to four alkyl chains bound per protein. The quantitative analysis of the isotherms reveals that Hill's equation fits well the binding data, leading to an estimate of the anticooperativity index and of the association constant as a function of the polymer structure.

Capillary electrophoresis frontal analysis: Principles and applications for the study of drug‐plasma protein binding

“…CE-FA has been used to measure binding of copper(II) to 1,10-phenanthroline and 2,2'-bipyridyl [52], drugs to cyclodextrins [43], and haptens to antibodies [53]. Furthermore, polymerprotein systems have been investigated by FACCE [47,[54][55][56][57][58][59][60]. It seems unlikely that similar size/charge ratios [41] HSA (rat plasma) Phenytoin, sulfathiazole, phenylbutazone, warfarin, diclofenac, ketoprofen…”

Determination of aggregation thresholds of UV absorbing anionic surfactants by frontal analysis continuous capillary electrophoresis

“…The resulting migration front of the free form is then usually exploited to yield the concentration of both forms and hence interaction parameters through mass balance equations. Following our previous determinations of the binding parameters pertaining to binary systems of biological interest by FACCE [21,22], we investigated in this work the auto-associative systems of anionic surfactants. Octyl and dodecylbenzenesulfonates were selected as model molecules for the assessment of this method, to allow easy direct absorbance monitoring.…”

Bioanalytical interaction studies executed by preincubation affinity capillary electrophoresis

“…FACCE electropherograms for the interaction of BSA with a hydrophobically modified sodium polyacrylate polymer are shown in Fig. 5 [77]. The similarity to CE-FA (Fig.…”

“…In all cases the McGhee-von Hippel interaction model [56] was found to describe the experimental data. FACCE has also been utilized to study the interaction of b-lactoglobulin and BSA with synthetic polyelectrolytes investigating the importance of hydrophobicity, pH, and ionic strength on protein-polyelectrolyte interactions [74,77,[100][101][102][103][104][105]. Some degree of uncertainty may relate to the actual determined values as pointed out by Winzor [79].…”