Interactions headgroup

Preliminary experiments with 6-CF loaded mixed vesicles of dipalmitoylphosphat-idylcholine (DPPC) and diacetylenic lipid (22) exhibit only a very slow release of 6-CF after the addition of phopholipase A2. Reasons for this may be headgroup interactions which decrease the enzymatic activity or the fact that multilamellar vesicles were used for this study. Further experiments will be carried out with giant liposomes (visible under the light microscope) which are unilamellar and provide a higher enclosure percentage and low surface curvature (see 4.3.2). 

They also studied the interaction of stearic acid (Cig) monolayers at the air-water interface with bivalent cations (Cd2+, Pb2 +, Ca2+, Ba2+, Cu2+, Ni2+, and Zn2+) in aqueous subphase using the IRRAS technique [45-47]. However, the information on molecular orientation was limited due to the use of unpolarized IR radiation. Recently, the headgroup interaction and chain orientation in the monolayers of stearic acid on pure water and ion (Ag+, Co +, Zn2+, and Pb2+)-containing subphases have been investigated using the IRRAS technique [48]. 

A Langmuir film consists of a monomolecular layer of amphiphiles spread onto a liquid subphase (usually water) via deposition from a volatile solvent. The solvent is allowed to evaporate, leaving the molecules free to orient themselves in the two-dimensional environment at the interface (with their hydrophilic headgroups in the water and their hydrophobic tails in the atmosphere above the water surface). The molecules dissolve or evaporate only to a very limited extent, due to the insolubility of the hydrocarbon chains and the strong headgroup interaction with the water, respectively. 

Lipids are a possible template for HZ biomineralization. As a bionucleating template, lipids can increase the solubihty of Fe(III)PPIX, localize high concentrations of Fe(III)PPIX with iron-hydrophobic headgroup interactions, and provide a layer of free heme intercalation. The propionate groups of free heme within the lipid layer draw into their positively charged Fe(III) centers, which weakens any hydrogen bonds with water and enables the hydrogen bonds of Fe(III)PPIX dimers. Fitch et al... 

The n-3 PUFAs are important components of cell membranes throughout the body, as they are incorporated into the phospholipids that form cell membranes. Each phospholipid molecule is comprised of a headgroup to which fatty acid esters are bound. There are two binding positions, termed 5 -l and sn-l. The acyl chains that bind to these headgroups interact with other chains in neighboring phospholipid molecules within the bilayer, and the level of chain interaction determines the biophysical properties of the membrane. The sn-l position is usually occupied by a saturated fatty acid the sn-2 position is usually occupied by a relatively unsaturated fatty acid chain. 

J.F. Nagle, Theory of Lipid Monolayer and Bilayer Phase Transitions Effect of Headgroup Interactions, T. Membr. Biol. 27 233 (1976). 

These results provide insight into the stabilization of diacetylene fdms. The headgroup interactions and alkyldiyne chain stacking should dominate die film... 

Headgroup interactions (electrostatic and/or hydrogen bonding) raise the temperature of transition. 

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