Microscopic and Spectroscopic Investigation Of: I. Copper-Additive Systems in Electroplating Bath. II. Supported Phospholipid Bilayer Systems

Abstract

Second, soft imaging mode of AFM and phase modulated ellipsometry are used to observe the phase transition process of supported lipid bilayer systems with and without the influence of other macromolecules. Addition of a weak polyelectrolyte, poly(methacrylic acid) (PMA), to a supported phospholipid bilayer depresses the melting temperature and alters the morphology of the bilayer in the gel phase. AFM study of the gel-fluid phase transition in supported phospholipid bilayers shows that at ∼5°C above Tm, AFM studies reveal the presence of a secondary phase transition. The secondary phase transition occurs as a consequence of decoupling between the two leaflets of the bilayer due to enhanced stabilization of the lower leaflet with either the support or the water entrained between the support and the bilayer. Addition of the transmembrane protein gramicidin A or construction of a highly defected gel phase results in elimination of this decoupling and removal of the secondary phase transition.