This work presents equilibrium and dynamic aspects for the adsorption at the air/liquid interface of two rat osseous plate alkaline phosphatase forms: DSAP, solubilized by a surfactant, C12E9, and containing a glycosylphosphatidylinositol (GPI) anchor; and PLSAP, resulting from phospholipase-C cleavage of the hydrophobic portion of the GPI anchor. Dynamic surface tension, gammadyn, and surface elasticity modulus, epsilon, were determined for PLSAP, DSAP and pure C12E9 solutions using harmonic oscillation and axisymmetric drop shape analysis Adsorption kinetics studies revealed that DSAP adsorbs thirty times faster than PLSAP, presenting a minimum in the curve. For DSAP/ C12E9 mixed system, e increases with concentration and a maximum appears at the critical aggregation concentration (CAC). For PLSAP, a continuous decreasing with concentration for gammadyn and epsilon was observed. For pure C12E9 solution, the elasticity modulus increases with concentration and epsilon values are higher when compared to the mixed system. A model based on the influence of the GPI anchor is proposed.
dynamic surface tension; adsorption kinetics; dilatational surface elasticity; alkaline phosphatase; axisymmetric drop shape analysis
