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Anomalous ph dependence of the coexistence pressure of the polymerizable two-chain n-lipid methyl-bis(pentacosadiinoyl-oxyethyl)-amine

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Wagner, D., Hofmann, U. G., Dorn, I., Schmitt, L., Tampe, R., & Gaub, H. E. (1997). Anomalous ph dependence of the coexistence pressure of the polymerizable two-chain n-lipid methyl-bis(pentacosadiinoyl-oxyethyl)-amine. European Biophysics Journal, 26(3), 271-275.


Cite as: http://hdl.handle.net/11858/00-001M-0000-0010-72AE-5
Abstract
Molecular films from polymeric materials play an important role in basic research as well as in technology. We have synthesized the double chain diacetylenic ammonium lipid N-bis-(10, 12-pentacosadiinoyl)-oxyethyl)-N-methyl-amine (ONCO). We have characterized monomolecular films at the air/water interface by means of microfluorescence filmbalance techniques and by atomic force microscopy (AFM). ONCO forms stable monomolecular films that exhibit a fluid-solid phase transition with a transition enthalpy of 90 kJ/mol at 10 degrees C and neutral pH. The coexistence pressure was found to decrease with decreasing protonation, which is in contrast to the commonly found Coulomb mechanism. A change in the chain packing due to a different nitrogen bond angle is discussed as a possible mechanism. This model is corroborated by the finding that crystals at high and at low pH differ in their polymerization properties as measured by microfluorescence. [References: 23]