The distribution of polyphosphoinositides in lipid films

Fluorescence microscopy of Langmuir films is used to determine the effect o f polyphosphoinositides (PPIs) on the structure of phosphatidylcholine-cont aining monolayers. Dramatic alterations in the texture of these films occur as the fraction of PPI in the film is altered. These changes depend on the ionic strength of the underlying subphase and can be accounted for by cons idering the electrostatic interactions among PPIs. Surface adsorption of a fluorescent peptide derivative based on the PPI binding site of the protein gelsolin co-localizes with PPI-rich domains. Localization of polyphosphoin ositides in domains within the inner leaflet of the plasma membrane is prop osed to be a key element in some aspects of intracellular signaling, and th ese data have implications for explaining the cause of restructuring of suc h domains. (C) 2001 Elsevier Science BN. All rights reserved.