Interaction strength between proteins and polyelectrolyte brushes: a small angle X-ray scattering study

• Published in: Physical chemistry chemical physics : PCCP 2011-10, Vol.13 (39), p.17599-17605
• Main Authors: HENZLER, Katja, HAUPT, Bjorn, ROSENFELDT, Sabine, HARNAU, Ludger, NARAYANAN, Theyencheri, BALLAUFF, Matthias
• Format: Article
• Language: English
• Subjects: Chemistry; Colloidal state and disperse state; Electrolytes - chemistry; Exact sciences and technology; General and physical chemistry; Lactoglobulins - chemistry; Membranes; Polystyrenes - chemistry; Scattering, Small Angle; Surface physical chemistry; X-Ray Diffraction
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/c1cp20663j

We present an investigation of β-lactoglobulin adsorption onto spherical polyelectrolyte brushes (SPBs) by small angle X-ray scattering (SAXS). The SPB consists of a polystyrene core onto which long chains of poly(styrene sulfonate) are grafted. The amount and the distribution of proteins adsorbed in the brush layer at low ionic strength can be derived from SAXS. The analysis of the SAXS data reveals additionally that some of the protein molecules form aggregates of about six monomers in the adsorbed state. Furthermore, the position and the amount of slightly bound protein can be detected by the combination of the SAXS results and the SPB loading after extensive ultrafiltration. The total amount of adsorbed protein is compared to data derived from isothermal titration calorimetry. The comparison of both sets of data demonstrates that the protein molecules in the inner layers of the spherical polyelectrolyte brush are firmly bound. Proteins located in the outer layers are only weakly bound and can be washed out by prolonged ultrafiltration.