Cupin-1.1 Adsorption Layers at the Surface of 8 M Urea Solutions

The adsorption layers of cupin-1.1, one of the two evolutionary conserved β-barrel domains of vicilin─the garden pea storage globulin─at the liquid-gas interface were studied by a few methods of the surface chemistry. The kinetic dependencies of the surface pressure of cupin-1.1 solutions in 8 M urea overlap in a single master curve if the surface pressure is plotted as a function of the normalized time. The analysis of the master curve allows separation of a few adsorption steps including the induction period, the regions of the diffusion-controlled and barrier-controlled adsorption kinetics, and a plateau region of slow adsorption. Another master curve can be constructed from the dependencies of the dynamic surface elasticity on surface pressure. This curve has some similarities with the corresponding results for recently studied cupin-1.1 spread layers on the surface of urea solutions and gliadin adsorption layers. There are also important distinctions with the master curve for adsorption layers of cupin-1.1 in the system without denaturants. This difference can be connected with the formation of larger and more rigid aggregates in pure water than the aggregates in urea solutions.