Anomalous swelling in phospholipid bilayers is not coupled to the formation of a ripple phase.
Aligned stacks of monomethyl and dimethyl dimyristoyl phosphatidylethanolamine (DMPE) lipid bilayers, like the much studied dimyristoyl PC (DMPC) bilayers, swell anomalously in a critical fashion as the temperature is decreased within the fluid phase towards the main transition temperature, T(M). Unlike DMPC bilayers, both monomethyl and dimethyl DMPE undergo transitions into a gel phase rather than a rippled phase below T(M). Although it is not fully understood why there is anomalous swelling, our present results should facilitate theory by showing that the formation of the phase below T(M) is not related to critical phenomena above T(M).
Mason
P C
PC
National Research Council, Steacie Institute for Molecular Sciences, Chalk River Laboratories, Chalk River, Ontario, Canada K0J 1J0.
Nagle
J F
JF
Epand
R M
RM
Katsaras
J
J
D004134:Dimyristoylphosphatidylcholine / Q000737:chemistry*; D008051:Lipid Bilayers / Q000737:chemistry*; D046911:Macromolecular Substances; D008560:Membrane Fluidity; D008567:Membranes, Artificial; D008968:Molecular Conformation; D009997:Osmotic Pressure; D044367:Phase Transition; D010714:Phosphatidylethanolamines / Q000737:chemistry*; D010743:Phospholipids / Q000737:chemistry; D013696:Temperature; D044366:Transition Temperature; D014867:Water / Q000737:chemistry*
D008051:Lipid Bilayers; D046911:Macromolecular Substances; D008567:Membranes, Artificial; D010714:Phosphatidylethanolamines; D010743:Phospholipids; D014867:Water; D004134:Dimyristoylphosphatidylcholine; C018525:1,2-dimyristoylphosphatidylethanolamine