Phase Transition of the Bilayer Membrane of Synthetic Dialkyl Amphiphiles as Studied by Differential Scanning Calorimetry

Abstract

Biophysikalische Chemie / Elektronenmikroskopie / Fliissige Kristalle / Membranen / Phasenum wandlungenThe phase transition behavior of dilute aqueous solutions of the bilayer membrane of dialkyl (CIz to CIS in most cases) amphiphiles was investigated by differential scanning calorimetry (DSC). The extent of the sample dispersion affected the DSC behavior for dialkyl amphiphiles with ammonium, phosphate and sulfonate head groups. The well-sonicated aqueous sample of the ammonium amphiphiles showed broader transition peaks at lower temperatures than the corresponding frozen sample did. The discrepancy became less pronounced when the interacting group was introduced at or near the head group. The dual DSC behavior was not observed for amphiphiles with nonionic (polyoxyethylene) and zwitterionic (phosphocholine) head groups. The phase transition temperature (0-80°C) was enhanced progressively with increasing alkyl chain lengths (C,z to CIS), but the transition enthalpy (2 -12 kcal/mol) did not obey simple relations.were shown to form bilayer membranes in these and other laboratories [3-111. We can now conclude that the bilayer formation is not a specific property of biolipids but a physicochemical property common to many of the dialkyl amphiphiles. These synthetic bilayer membranes, especially dialkylammonium membranes, has been examined concerning their structures, physicochemical properties, and physical and chemical functions [ 121.

Anionic Hapten-Antibody Reactions on Various Cationic Bilayer Membrane Systems

“…8 No turbidity change due to hapten-antibody reaction was detected in the presence of either an anionic 2C 14 P0 4 H and a zwitterionic 2C 14-gly-PC at temperature range of 30-70oC ( Figure 2 …”

Formation of Molecular Membranes in Water from Ionene Oligomers and Related Amphiphiles

“…The details are described elsewhere. 16 Molecular weights were determined by a small-angle light scattering apparatus with a He-Ne laser source (Toyo Soda, LS-8). 17 The sample concentration was 5mg/50ml (2.5x 10-4 -3.8x 10-4 unit M).…”

“…19 The crystal-to-liquid crystal phase transition is a fundamental property of the bilayer membrane, and has been observed for representative synthetic bilayers. 16 Figure 3 displays a DSC chart for C 20 ionene. The endothermic peak (peak top, 53°C) is apparently attributed to the phase transition.…”

Partition Coefficients of 1-Alkanols between Water and DDAB Vesicle Membrane Determined by Differential Conductivity Method

“…Didodecyldimethylammonium bromide (DDAB) is a doublechained cationic surfactant, and is the first synthetic amphiphile that was reported to form vesicles in water under ultrasonic irradiation 6) . The following studies have been published on DDAB vesicles: (1) size and stability 7) , (2) gel-to-liquid-crystalline phase transition temperature 8) , (3) solubilization of organic compounds 9) , (4) concentrationdependent change in aggregation states 10) . So far, the studies on solubilization of amphiphilic compounds such as alkanols, surfactants, and anesthetics into vesicles have been performed with many methods from the viewpoint of fundamental research necessary for their applications 11) .…”