[Helix-globule transitions of polypeptides selectively reacting with the interface]

An analytical theory of helix-coil transitions for polypeptides in a solution near a flat and homogeneous interface is given. The following cases were considered: a) only the helical parts are absorbtively active; b) only the coiled sections of the chain are active in adsorption. It has been shown that the binding of the polymer chain to the surface is a result of a phase transition of a second order, moreover in case a) the presence of a secondary structure abruptly increases the ability of the macromolecules to bind to the interface. This largely increases the stability of the helical structure of the chain and leads to a practically complete spiralization of the macromolecule. The profile of the conformational transitions was strictly asymmetrical which is typical for the phase transitions. In case b) the process of binding resembles the adsorbtion of the Gaussian coils. In this case the rate of spiralization of the chain decreases in the course of binding and the degradation of the secondary structure is significant even if the helical state in volume is stable. The profile of the transition remains qualitatively similar to the helix-coil transition in volume but is displaced to the region of larger equilibrium constants.