Domain formation monolayers

Siepmann JI and IR McDonald 1993a. Domain Formation and System-size Dependence in Simulatio of Self-assembled Monolayers. Langmuir 9 2351-2355. 

This review emphasizes an intriguing and potentially useful aspect of the polymerization of lipid assemblies, i.e. polymerization and domain formation within an ensemble of molecules that is usually composed of more than one amphiphile. General aspects of domain formation in binary lipid mixtures and the polymerization of lipid bilayers are discussed in Sects. 1.1 and 1.2, respectively. More detailed reviews of these topics are available as noted. The mutual interactions of lipid domains and lipid polymerization are described in the subsequent sections. Given the proper circumstances the polymerization of lipid monolayers or bilayers can lock in the phase separation of lipids, i.e. pre-existing lipid domains within the ensemble as described in Sect. 2. Section 3 reviews the evidence for the polymerization-initiated phase separation of polymeric domains from the unpolymerized lipids. 

Domain formation in binary mixtures of a polymerizable lipid and non-polymerizable lipid is well established for diacetylenic lipids. The rigid diacetylenic unit facilitates the formation of enriched domains in the condensed phase of monolayers or the solid-analogous phase of bilayers. Since diacetylenes polymerize most readily in solid-like states, most studies have focused on conditions that favor domain formation. Only in the case of a mixture of a charged diacetylenic lipid and a zwitterionic PC was phase separation not observed. Ringsdorf and coworkers first reported the polymerization of a phase-separated two-dimensional assembly in 1981 [33], Monolayer films were prepared from mixtures consisting of a diacetylenicPC (6) (Fig. 5) and a nonpolymerizable distearoyl PE (DSPE). 

Israelachvili, J. 1994. Self-assembly in two dimensions Surface micelles and domain formation in monolayers. Langmuirl 0 3774—3781. 

McConlogue, C.W. Vanderlick, T.K. A close look at domain formation in DPPC monolayers. Langmuir 1997,13, 7158. 

Kimizuka, N., and Kunitake, T. Molecular Orientation and Domain Formation in Surface Monolayers of Azobenzene Containing Amphiphiles and Their Polyion Complexes. Chem. Lett. 827 (1988). 

The influence of CHL and Q3P on film morphology in monolayer mixtures with DPPC has been studied. Monolayers of DPPC as well as it mixtures tvith cholesterol, transferred by HP method, showed a molecularly smooth structure of uniform thickness. The addition of Q3P or CHL to DPPC, as investigated by AFM phase measurements, showed that a marked phase separation occurs in DPPC/Q3P mixtures or DPPC/SM/CHL films at small concentration of the alcohols, proving raft domain formation in the case of DPPC/SM/CHL films. 

D.W. Grainger, A. Reichert, H. Rings-DORE, and C. Salesse. An enzyme caught in action direct imaging of hydrolytic function and domain formation of phospholipase A.2 in phosphatidylcholine monolayers. FEBS Lett., 1989, 252, 71-82. 

Lateral transport phenomena can be observed for example as surface self-diffusion (Vollhardt et al. 1980), from concentration gradients in surface films as the result of compression or expansion of soluble or insoluble monolayers (Dimitrov et al. 1978), from the effect of aggregation or domain formation in such monolayers (Lucassen-Reynders 1987), or from domain movements in monolayers induced by an electric field (Heckl et al. 1988). 

Pure fatty acids on acidic aqueous subphases give surface pressure-surface area isotherms wifh a distinct plateau and a sharp pressure rise when the mono-layer is formed (see Sec. 1.7). This behavior corresponds to domain formation at low pressure (<2 mN/m), change of packing within the domains at about 7 mN/m, and formation of a continuous monolayer at surface pressure of >20 mN/m. The average molecular area of fatty acids is about 22 A. X- ray diffraction of the monolayers has been used to characterize the various orientations of... 

Domain formation already occurs at the air-water interface directly after spreading. Film compression therefore only reduces the free area present between the domains. Hole free films are only obtained, if the monolayers are compressed to Il-values II2, which correspond to the steep rise of the Il-A-isotherm shown in Fig. 15. Finally, upon transfer of the film onto substrates the domains become oriented in the dipping direction. 

Siepmann, J. I., and McDonald, I. R. (1993) Domain Formation and System-Size Dependence in Simulations of Self-Assembled Monolayers, Langmuir 9, 2351-2355. 

Figure 20.4 A model for the mechanism of ceramide domain formation and invagination in a PC/SM membrane, induced by the asymmetric action of SMase. For the sake of clarity only the monolayer subject to the action of SMase is illustrated. The symbols used for the lipid headgroups are (O) SOPC, ( ) SM, ( ) ceramide. The scale bar corresponds to 50 pm.

Enzyme Substrate Interaction Specific Recognition, Function and Domain Formation of Phosphoiipase A2 at Lecithin Monolayers... 

In a mixed monolayer of IvsoPPC and palmitic acid d ) without DPPC, neither phase separation within the monolayer nor protein domain fonnation after injection of the enzyme can be detected. Uncleaved lecithin thus seem to be necessary to induce domain formation protein aggregatioa... 

Ahlers, M., Blankenburg, R., Grainger, D. W., Meller, P., Ringsdorf, H. and Salesse, C. (1989) Specific recognition and formation of two-dimensional streptavidin domains in monolayers Applications to molecular devices. Thin Solid Films 180,93-99. 

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