Organic molecules, interaction with micelles

In emulsion polymerization, a solution of monomer in one solvent forms droplets, suspended in a second, immiscible solvent. We often employ surfactants to stabilize the droplets through the formation of micelles containing pure monomer or a monomer in solution. Micelles assemble when amphiphilic surfactant molecules (containing both a hydrophobic and hydrophilic end) organize at a phase boundary so that their hydrophilic portion interacts with the hydrophilic component of the emulsion, while their hydrophobic part interacts with the hydrophobic portion of the emulsion. Figure 2.14 illustrates a micellized emulsion structure. To start the polymerization reaction, a phase-specific initiator or catalyst diffuses into the core of the droplets, starting the polymerization. 

Organic molecules are solubilized by the organic constituents of a micelle. In small micelles the molecules lie close to the interface, while in large microemulsions considerable penetration into the core is observed (1.). Inorganic materials are quite polar and have little interaction with the organic components of the micelle. However, the micelle counterions,... 

This shows that the cytochrome c extraction into an organic phase is carried out at a very low DOLPA concentration, in which reverse micelles cannot be formed. Also, the molar ratio required for the complete protein extraction was approximately 20, which corresponds to the number of cationic charged residues available for the electrostatic interaction with an anionic surfactant in one cytochrome c molecule. These results support the concept that proteins are extracted by electrostatic interactions with surfactant molecules, and that the existence of reverse micelles is not necessary for causing protein transfer, as mentioned above. 

Lipids are building blocks of model and real membranes, which can be combined with proteins and some other important biomolecules to simulate real membranes. The simplest model is hence the self-assembly of only one component of the complex membrane, in this case the lipids. These mono-component lipidic models are often employed in studies as their interaction with small molecules mimics the actual relationship between the cell membrane and a substrate. A commonly employed amphiphatic lipid, dipalmitoyl phosphatidylcholine (DPPC) (Figure 4.6.2), has been widely used to construct these cell membrane motifs, due to its high content in animal cells, and thus its tendency to mimic a valid animal ceU. The supramolecular organization of these (a) DPPC amphiphatic molecules lead to a (b) Langmuir monolayer, (c) bilayer, (d) micelle, and (e) vesicle, which are the available levels of modeling to mimic the cellnlar membrane. 

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