Synergetic effect of sodium polystyrene sulfonate and guanidine hydrochloride on the surface properties of lysozyme solutions

Abstract

A study of the dilational surface viscoelastic properties of mixed solutions of lysozyme and denaturing agents with different chemical natures allows us to characterize the changes of protein tertiary structure in the surface layer upon adsorption at the liquid-gas interface. We show that guanidine hydrochloride (GuHCl) and urea influence the dynamic surface properties of lysozyme solutions less than the properties of previously studied solutions of bovine serum albumin and b-lactoglobulin. Although the addition of sodium polystyrene sulfonate (PSS) changes the kinetic dependencies of the surface properties and leads to the formation of large aggregates in the bulk phase, the dependencies of the dynamic surface elasticity on the surface pressure almost coincide with the results for pure lysozyme solutions thereby indicating the preservation of the adsorption layer structure. At the same time, the simultaneous addition of PSS and GuHCl to lysozyme solutions results in a strong synergistic effect: the kinetic dependency of the dynamic surface elasticity becomes non-monotonical and similar to that for solutions of amphiphilic polymers and non-globular proteins. The local maximum of this dependency indicates the destruction of the protein globular structure and formation of the distal region of the surface layer. The simultaneous addition of PSS and urea to lysozyme solutions does not lead to a similar effect. These results confirm different mechanisms of protein denaturation under the influence of urea and GuHCl, and the important role of electrostatic interactions in the latter case. † Electronic supplementary information (ESI) available: Additional information about the surface elasticity of mixed lysozyme-PSS-NaCl and lysozyme-urea solutions and additional DLS data. See

CnTAB/polystyrene sulfonate mixtures at air–water interfaces: effects of alkyl chain length on surface activity and charging state

“…Consequently, NR was often applied to polyelectrolyte/surfactant mixtures at airwater interfaces. 16,[39][40][41][42][43][44] In fact, the effect of the surfactant chain length on the thickness of NaPSS/CnTAB layers adsorbed to the air-water interface has been studied with NR by Taylor et al 14 However, they varied the surfactant concentration (as opposed to polyelectrolyte concentration in our work) and did not report on the differences in the binding behavior and the surface charge of polyelectrolyte-surfactant complexes at the air-water interface.…”

Impact of a Reducing Agent on the Dynamic Surface Properties of Lysozyme Solutions

“…Additionally, no kinetic dependencies of the dynamic surface elasticity had local maxima, and they remained monotonic Fig. 2 , unlike the corresponding results for lysozyme/GuHCl solutions, where the local maxima were related to globule unfolding 27,31 . Thus, the lysozyme globular structure was probably mostly preserved in the surface layer.…”

Adsorption of Denaturated Lysozyme at the Air–Water Interface: Structure and Morphology

“…Whereas the denaturation of the globular structures of bovine serum albumin and β-lactoglobulin occurs at lower denaturant concentrations in the surface layer than in the bulk phase, − Perriman et al have observed the opposite behavior in lysozyme solutions . This result agrees with dilational surface rheology measurements. , The addition of strong denaturants to dilute lysozyme solutions leads to smoother changes of the kinetic dependencies of the dynamic surface elasticity than for solutions of other globular proteins, where strong peaks of the surface elasticity are observed. − Moreover, the addition of urea does not change the shape of the corresponding kinetic curves up to very high concentrations of the denaturant (∼10 M) …”

“…In this case the adsorption is slow enough and the main steps of this process can be followed by measuring the kinetic dependencies of surface properties. 10,11 For reference, a description of the kinetic dependencies of the surface tension and the real part of the dynamic surface elasticity is given for solutions of hydrogenous lysozyme without addition of NaCl measured under dynamic conditions involving sinusoidal oscillations of the surface area ( Fig. 1).…”

“…Even in the case of one of the most studied model proteins, lysozyme (LYS), the conclusions of different research groups are frequently inconsistent. The radiolabeling technique, neutron reflectometry (NR), , ellipsometry, and surface dilational rheology − do not indicate significant changes of the tertiary structure at the air–water interface. On the contrary, external reflection FTIR spectroscopy shows clear changes of the lysozyme secondary structure at the air–water interface in comparison with the adsorption layers of other proteins, suggestive of possible concomitant changes of the tertiary structure.…”