Lecithin zwitterionic head group

The solubilization of water in lecithin-reversed micelles has been found to be an exothermic process. This finding confirms that water interacts with the zwitterionic head group of lecithin, promoting the formation of strong intermolecular H bonds [104]. 

Totally synthetic bilayers show liquid crystalline properties similar to those of lecithin bilayers (Nagamura et al., 1978 Kano et al., 1979). Bilayer formation has also been observed for dialkyl compounds with anionic head groups such as [2] and [3] (Kunitake and Okahata, 1978a Mortara et al., 1978), and with nonionic and zwitterionic head groups as in [4] and [5] (Okahata et al., 1978a). 

To better identify the boundaries of the oil-in-water phase and how its characteristics vary with small fluctuations in composition, we extended our analyses of the ternary phase diagram to include more detailed characterization of each phase and a higher resolution map of the oil-water phase. Two lipids— DOPA, an anionic lipid, and lecithin, a zwitterionic neutral lipid—were compared to determine the effect of lipid head group. Five different characterization methods were employed (1) visual classification of the phases, (2) buoyant density, (3) fluorescence quenching, (4) FT-IR, and (5) Cryo-TEM. The rationale for each technique is summarized in Table 15.2. A flow chart for utilizing the information obtained from these methods was developed to objectively evaluate the oil-in-water phase (Fig. 15.5). 

---