Persistence of phase coexistence in disaturated phosphatidylcholine monolayers at high surface pressures
Persistence of phase coexistence in disaturated phosphatidylcholine monolayers at high surface pressures
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DOI：
10.1016/s0006-3495(99)77143-2
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发表时间：
1999-12-01
影响因子：
3.4
通讯作者：
Hall, SB
中科院分区：
文献类型：
--
作者：
Crane, JM;Putz, G;Hall, SB
Prior reports that the coexistence of the liquid-expanded (LE) and liquid-condensed (LC) phases in phospholipid monolayers terminates in a critical point have been compromised by experimental difficulties with Langmuir troughs at high surface pressures and temperatures. The studies reported here used the continuous interface of a captive bubble to minimize these problems during measurements of the phase behavior for monolayers containing the phosphatidylcholines with the four different possible combinations of palmitoyl and/or myristoyl acyl residues. Isothermal compression produced surface pressure-area curves for dipalmitoyl phosphatidylcholine (DPPC) that were indistinguishable from previously published data obtained with Langmuir troughs. During isobaric heating, a steep increase in molecular area corresponding to the main LC-LE phase transition persisted for all four compounds to 45 mN/m, at which collapse of the LE phase first occurred. No other discontinuities to suggest: other phase transitions were apparent. Isobars for DPPC at higher pressures wet-a complicated by collapse of the monolayer, but continued to show evidence up to 65 mN/m for at least the onset of the LC-LE transition. The persistence of the main phase transition to high surface pressures suggests that a critical point for these monolayers of disaturated phospholipids is either nonexistent or inaccessible at an air-water interface.
