Cooperativity and kinetics of phase transitions in nanopore-confined bilayers studied by differential scanning calorimetry.
The first-order nature of the gel-to-liquid crystal phase transition of phospholipid bilayers requires very slow temperature rates in differential scanning calorimetry (DSC) experiments to minimize any rate-dependent distortions. Proportionality of the DSC signal to the rate poses a problem for studies of substrate-supported bilayers that contain very small volumes of the lipid phase. Recently, we described lipid bilayers self-assembled inside nanoporous substrates. The high density of the nanochannels in these structures provides at least a 500-fold increase in the bilayer surface area for the same size of the planar substrate chips. The increased surface area enables the DSC studies. The rate-dependent DSC curves were modeled as a convolution of a conventional van't Hoff shape and a first-order decay curve of the lipid rearrangement. This analysis shows that although confinement of bilayers to the nanopores of approximately 177 nm in diameter results in a more than threefold longer characteristic time of the lipid rearrangement and a decrease in the cooperative unit number, the phase transition temperature is unaffected.
Alaouie
Ali M
AM
Smirnov
Alex I
AI
D002152:Calorimetry, Differential Scanning / Q000379:methods*; D003198:Computer Simulation; D004134:Dimyristoylphosphatidylcholine / Q000032:analysis / Q000737:chemistry*; D007700:Kinetics; D008051:Lipid Bilayers / Q000032:analysis / Q000737:chemistry*; D008081:Liposomes / Q000737:chemistry*; D008956:Models, Chemical; D008968:Molecular Conformation; D049329:Nanostructures / Q000032:analysis / Q000737:chemistry* / Q000648:ultrastructure; D044367:Phase Transition; D016062:Porosity; D013499:Surface Properties; D013696:Temperature
D008051:Lipid Bilayers; D008081:Liposomes; D004134:Dimyristoylphosphatidylcholine