Surfactants phospholipids and

Fig. 1.4. Examples of surfactants, phospholipids and polymers with covalently bound probes. 1 2-(9-anthroyloxy)stearic acid. 2 6-(9-anthroyloxy)stearic acid.

This section will focus primarily on the development of nonviral vectors that are based on surfactants, phospholipids, and natural or synthetic polymers for their application to the delivery of macromolecules, mainly of genetic materials such as DNA or RNA. Development of safe and efficient vectors will expedite the success of human gene therapy, which has captured the attention recently of the public and the biomedical research community. Even though more and more new delivery vectors are being introduced into the scientific milieu with enhanced efficiency, it should be emphasized that safety always goes first, especially after the tragedy of J. Gelsinger in 1999. 

The h(Cei) dependences (at pG = const and t = const) are studied also for other surfactants, phospholipids and polymers, and they have proved to be very informative with respect to not only the CBF/NBF transition and Cei,cr values, but also surface forces acting in black foam films (see Sections 3.3. and 3.4). 

Torday J, Rehan V (2011) Neutral lipid trafficking regulates alveolar type II cell surfactant phospholipid and surfactant protein expression. Exp Liang Res 37(6) 376-386... 

The reason(s) for the difference in equilibrium surface tensions of airway and alveolus are unknown, but they may reflect differences in the composition, concentration, or both, of the surfactant of the two compartments. As the rate of adsorption of lipids to the film interface depends on both the composition and concentration of the surfactant phospholipids and the associated surfactant proteins (23,65), the low SP-A and absent SP-B and SP-C in the pig tracheal fluid in the foregoing experiments (44) may account for the higher static adsorptions observed in the tracheal fluids from this species. 

Recent evidence indicates that the mechanisms of inhibition by proteins may involve competition between the surfactant phospholipids and proteins for space at the air-liquid interface (210-212). In certain systems, the inhibitory effect of a protein on surfactant activity can be reduced by increasing the surfactant concentraton in the assay (210,211). 

Phospholipids and sphingolipids are involved in several disease processes, including respiratory distress syndrome (lack of lung surfactant), multiple sclerosis... 

Ruckenstein and Li proposed a relatively simple surface pressure-area equation of state for phospholipid monolayers at a water-oil interface [39]. The equation accounted for the clustering of the surfactant molecules, and led to second-order phase transitions. The monolayer was described as a 2D regular solution with three components singly dispersed phospholipid molecules, clusters of these molecules, and sites occupied by water and oil molecules. The effect of clusterng on the theoretical surface pressure-area isotherm was found to be crucial for the prediction of phase transitions. The model calculations fitted surprisingly well to the data of Taylor et al. [19] in the whole range of surface areas and the temperatures (Fig. 3). The number of molecules in a cluster was taken to be 150 due to an excellent agreement with an isotherm of DSPC when this... 

Type 1 gels are mesophases that are so highly ordered that they resist disruption of their structure and are thus extraordinarily viscous, to the point of appearing solid-like, even though no high molecular weight species need be present in the system. Surfactants, both synthetic (e.g., sodium dodecylsulfate) and natural (e.g., phospholipids), and clays are typical representatives of this class. 

Lukac S (1984) Thermally induced variations in polarity and microviscosity of phospholipid and surfactant vesicles monitored with a probe forming an intramolecular charge-transfer complex. J Am Chem Soc 106 4386 -392... 

The situation is, however, different in the alveolar region of the lung where the respiratory gas exchange takes place. Its thin squamous epithelium is covered by the so-called alveolar surface liquid (ASL). Its outermost surface is covered by a mixture of phospholipids and proteins with a low surface tension, also often referred to as lung surfactant. For this surfactant layer only, Scarpelli et al. [74] reported a thickness between 7 and 70 nm in the human lung. For the thickness of an additional water layer in between the apical surface of alveolar epithelial cells and the surfactant film no conclusive data are available. Hence, the total thickness of the complete ASL layer is actually unknown, but is certainly thinner than 1 gm. 

The positively charged amino acids promote the interaction between the peptide and the negatively charged head groups of the phosphatidylgly-cerol (123-125). The purpose of this particular property has been proposed to facilitate the transition of surfactant phospholipid membranes from the lamellar body to the alveolar spaces (123). 

Respiratory effects are more likely to occur after inhalation exposure to high concentrations of chloroform. It has been demonstrated that chloroform has a destructive influence on the pulmonary surfactant (Enhoming et al. 1986). This effect is probably due to the solubility of phospholipids in the surfactant monolayer and can cause collapse of the respiratory bronchiole due to the sudden increase in inhalation tension. Immediate death after chloroform inhalation may be due principally to this effect in the lungs (Fagan et al. 1977). It is unlikely that exposure levels of chloroform in the general environment or at hazardous waste sites would be high enough to cause these severe respiratory effects. 

According to Helenius and Simons (30) solubilization of the membrane is preceded by saturation of the bilayer with surfactant. Certainly critical surfactant/phospholipid ratios must be attained before membrane disruption occurs. 

Preparation methods of vesicles have been known and employed for various purposes the ultrasonic irradiation method, and the injection method, for example. In addition to them. there has appeared a novel method, which consists of solubilizing phospholipids in surfactant solution, and subsequently removing the surfactant by... 

Surface Interaction of Calcium and ATP with Phospholipids and Other Surfactants... 

H Buenger, U Pison. Quantitative analysis of pulmonary surfactant phospholipids by high performance liquid chromatography and light scattering detection. J Chromatogr B 672 25-31, 1995. 

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