Effect of serum proteins on an exogenous pulmonary surfactant: ESR analysis of structural changes and their relation with surfactant activity

► We examine the effects of human serum, bovine serum albumin, gamma globulin and cholesterol on dynamic and structural properties of surfactant. ► Serum modified aggregation state increases the inactive subtype, decreases the fluidity in the polar region and inactivates EPS. ► A serum component, different from albumin, gamma globulin and cholesterol, may be responsible for the loss of surfactant activity. ► There is a correlation between the fluidity in the polar region of the surfactant bilayer and the surface activity. ► Serum leads to increased structural rigidity in the polar area of the phospholipid bilayer, which compromises the surfactant performance.