Polymer-protein association isotherms

Figure 7.7. Association isotherms of micelles (TX 100) or the protein bovine serum albumin on azobenzene-modified poly (sodium acrylate) in dilute water solution, as measured from capillary electrophoretic analysis. Closed symbols dark-adapted samples, open symbols samples exposed to UV light (365 nm). (a) Polymer, as shown in Fig. 7.1, with n = 5 and x=7%, (b) n = 12 and x=3%.

Porcar I., Cottet H., Gareil P, Tribet C. Association between protein particles and long amphiphilic polymers effect of the polymer hydrophobicity on binding isotherms. Macromolecules 1999 32(ll) 3922-3929. 

The adsorption of large polar molecules is expected to produce large unfolding of the protein, possibly terminating with its denaturation. Denaturation can be considered as a phase transition, characterized by a jump discontinuity of the adsorption isotherm, between native-like state (with bulk fractal dimension D = 3 and surface fractal dimension D = 2.1 - 2.2) and the denatured state (in which the protein can be seen as an excluded-volume polymer with D =5/3 [57]). Denaturation is therefore associated with a sudden variation of the fractal dimension of the protein. 

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