Phase separation of phospholipid monolayers induced by membrane penetration of human apolipoprotein H

In this paper we studied the interaction of apolipoprotein H (ApoH), an autoantigen or cofactor in antiphospholipid syndrome, with phospholipid monolayers by means of fluorescence microscopy and surface film balance. Observations with fluorescence microscopy indicate that: (1) ApoH can penetrate into both anionic and neutral phospholipid monolayers; (2) the membrane penetration of ApoH may induce phase separation of the phospholipid monolayers; and (3) ApoH prefers to penetrate into the region of the phospholipid monolayer that is in fluid state.