Dipalmitoyl-phosphatidylcholine DPPC /water

Since optical measurements of monolayers at the water-oil interface are rather difficult to carry out, a configuration was suggested where a monolayer at the water-air interface was in contact with an oil lens which was partly wetting the monolayer [23]. The thermodynamic relation between this monolayer and that residing at the water-oil interface was discussed. This configuration was utilized in the X-ray diffraction experiments [24] where the structural changes of dipalmitoyl phosphatidylcholine (DPPC) and DPPE were followed. 

Cantrell et al. (2003) studied the quenching of 02 by several dietary carotenoids in dipalmitoyl phosphatidylcholine (DPPC) unilamellar liposomes. These workers used water soluble and lipid soluble 02 sensitizers so that a comparison of the efficiencies of quenching 02 generated within and outside the membrane model could be made. Perhaps surprisingly there was little difference in the efficiency of quenching in either situation. Typical results are presented in Table 14.3 (taken from Cantrell et al. (2003 and 2006)). 

GlvcoDhorin-Lioid Monolayers at the Air-Water Interface. Further to the study of pure glycophorin monolayers we investigated the interaction between the glycophorin and dipalmitoyl-phosphatidylcholine (DPPC) in mixed monolayers at the air-water interface (27). Pure DPPC undergoes the characteristic liquid expanded (L ) to intermediate state (I) transition in monolayers at temperatures below the chain-melting temperature (- 42 C) of... 

Figure 5.3. Dipalmitoyl phosphatidylcholine (DPPC) transferred on to a solid support at a rather high transfer speed of 1000 pm/s at a lateral surface pressure of 3.0 mN/m Dynamic scanning force microscopy (SFM) images provide evidence for the formation of a regularly structured surface, revealing channels with a width of about 200 nm separated by 800 nm wide stripes of the monomolecular film. The main figure represents phase and and the inset (4x4 pm ) topography imaging. The monolayer was prepared on pure water at room temperature A change in the temperature influences the periodicity. (From M. Gleiche and L. F. Chi), Nature, 403, 2000, 173)...

Surfactant is a lipid-protein complex that is synthesized and released hy alveolar type II epithelial cells. This complex surface-active compound contains both hydrophobic and hydrophilic regions to allow the molecule to spontaneously adsorb to and form monolayers along the air-liquid interface. The role of surfactant in pulmonary fluid mechanics depends on its natural ability to disrupt intermolecular forces by interfering with the attractive forces between water molecules at the interfacial surface—thus lowering the surface tension. While this surfactant mixture is largely comprised of lipids (90%), the surfactant proteins (10%) are required for normal function (Hall et al. 1992 Yu and Possmayer 1993). Finally, the molecule dipalmitoyl phosphatidylcholine (DPPC) makes up 80% of the phospholipid and is largely responsible for the ultra-low surface tensions necessary for respiratory function (<5 dyn/cm) (Klaus et al. 1961 Hawco et al. 1981 Tchoreloff et al. 1991). 

Such calibration measurements were made for water penetrating dipalmitoyl phosphatidylcholine (DPPC) phospholipid model membranes. It was concluded that the concentration of free water near the spin-labelled 4th carbon atom along the lipid chain is 5.2 M for cholesterol-free, and 7.2 M for cholesterol-containing membranes, respectively. Another example is a study of the penetration of glycerol-ds across model membranes quantitative assessment of the glycerol concentration at the middle of the bilayer resulted in a value of 0.4 M ( 3% v/v). 

The TOAC spin label is used to substitute for Aib in trichogin, at the three possible sites. The spin-labelled peptide was studied by ESEEM in D20-hydrated dipalmitoyl phosphatidylcholine (DPPC), " and egg phosphatidylcholine (ePC), model membranes. To determine the localization of the peptide, reference data on the density profile of water in phospholipid model membranes were obtained from ESEEM of spin-labelled lipids. At low peptide concentration (peptide/lipid ratio less than 1 200 mol mol ), ESEEM amplitudes were found to be similar for labels close to the N-terminus and to the C-terminus. The ESEEM amplitudes turned out to be close to those found previously for lipids spin-labelled at carbon-atom of the lipid acyl chain nearest to the membrane surface. Therefore, it can be concluded that the peptide is oriented parallel to the membrane surface. The molecular structure of the peptide in the lipid environment that is estimated from these data is shown in Fig. 7. ... 

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