The dynamic surface properties of green fluorescent protein and its mixtures with poly(N,N-diallyl-N-hexyl-N-methylammonium chloride)

Surface Properties of Protein–Polyelectrolyte Solutions. Impact of Polyelectrolyte Hydrophobicity

“…At low concentrations (2 × 10 –5 –2 × 10 –4 g/L), PDAHMAC decreases the rate of changes of the dynamic surface properties for BLG–PDAHMAC and GFP–PDAHMAC solutions presumably due to the formation of globular protein–polyelectrolyte complexes and their relatively slow diffusion to the surface (Figure A). The polyelectrolyte also increases the induction period in the latter case . For BLG solutions, the effect of the polyelectrolyte at low concentrations is not so dramatic but one can also observe an induction period of the kinetic dependencies of surface properties at a concentration of 2 × 10 –4 g/L, corresponding to the formation of a heterogeneous adsorption layer (Figures and ) .…”

“…38 In the polyelectrolyte concentration range of 2 × 10 −3 to 2 × 10 −2 g/L, the kinetic dependencies of the dynamic surface elasticity for lysozyme−PDAHMAC, BLG−PDAHMAC, and GFP−PDAHMAC also have local maxima (Figure 2a,b). 42 At the same time, the surface pressure corresponding to the range of these maxima, 5−7 mN/m, is the same for these three systems and differs from the values that were determined for the maxima for lysozyme−PDAHMAC and BSA−PDAHMAC solutions at lower concentrations. The surface pressure corresponding to the protein unfolding is higher than 7 mN/ m and not less than 10 mN/m.…”

“…The polyelectrolyte also increases the induction period in the latter case. 42 For BLG solutions, the effect of the polyelectrolyte at low concentrations is not so dramatic but one can also observe an induction period of the kinetic dependencies of surface properties at a concentration of 2 × 10 −4 g/L, corresponding to the formation of a heterogeneous adsorption layer (Figures 1 and 2). 53 In this case, the adsorption of the complexes results in the formation of some islands of the surface condensed phase, and the surface properties start to change only when these islands start to interact.…”

“…The obtained results for mixed BLG−PDAHMAC, BSA− PDAHMAC, and lysozyme−PDAHMAC solutions can be compared with previously obtained data for solutions of the green fluorescent protein (GFP)−PDAHMAC complexes. 42 For all these systems, the polyelectrolyte has a strong impact on the dynamic surface properties. At pH 7, the complexes between the proteins and the positively charged polyelectrolyte are formed even in the case of positively charged lysozyme, presumably due to negatively charged patches on the surface of the protein globules and via hydrophobic interactions.…”

“…41 At the same time, the interactions of proteins with various denaturants, in particular with synthetic polyelectrolytes, lead to different types of these dependencies. [37][38][39]42,46 For example, the kinetic dependencies of the dynamic surface elasticity of the solutions of bovine serum albumin (BSA) with poly(N,N-diallyl-N,N-dimethylammonium chloride) (PDAD-MAC) and sodium poly(styrene sulfonate) (PSS) exhibit local maxima, indicating the destruction of the protein tertiary structure. 38,46 The response of dynamic surface properties of lysozyme solutions to additions of polyelectrolytes is weaker and a pronounced local maximum of the surface elasticity was observed only when PSS was applied together with guanidine hydrochloride.…”