Modification of a supported lipid bilayer by polyelectrolyte adsorption.
Addition of a weak polyelectrolyte, poly(methacrylic acid) (PMA), to a supported phospholipid bilayer made from 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) depresses the melting temperature and alters the morphology of the bilayer in the gel phase. Ellipsometry measurements show that PMA adsorption lowers the phase transition temperature by 2.4 degrees C. Atomic force microscopy (AFM) showed no visible contrast in the fluid phase (above the melting temperature) but a rich morphology in the gel phase. In the gel phase, adsorption leads to formation of significantly less mobile phospholipid islands and other defects. One consequence of this lower mobility is a decrease in the implied cooperativity number of the phase transition, N, when polymer is added. Additionally, AFM images of the gel-phase bilayer show a highly defected structure that anneals significantly more slowly than in the absence of adsorbed polymer. Tentatively, we suggest that PMA preferentially decorates island and defect edges of the DMPC bilayer.
Feng
Z Vivian
ZV
Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana 61801, USA.
Granick
Steve
S
Gewirth
Andrew A
AA
D000327:Adsorption; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D004134:Dimyristoylphosphatidylcholine / Q000737:chemistry*; D008051:Lipid Bilayers / Q000737:chemistry*; D018625:Microscopy, Atomic Force; D008954:Models, Biological; D011109:Polymethacrylic Acids / Q000737:chemistry*; D013696:Temperature
D008051:Lipid Bilayers; D011109:Polymethacrylic Acids; D004134:Dimyristoylphosphatidylcholine