Phospholipids labelled

Interpreting Scientific Illustrations Draw the general structure of a phospholipid. Label the polar and nonpolar portions of the structure. 

In 1955 Blomstrand [93] fed phospholipids labeled with [ " C]palmitic acid to rats with both the bile and thoracic duct cannulated. The results indicated that in this situation 68% of the fatty acids were absorbed and that bile was not obligatory for absorption of phospholipid fatty acid. The distribution of the labeled fatty acid in the thoracic duct lipids showed the same pattern as after feeding the free fatty acid, indicating that the phospholipids had been hydrolyzed before absorption. The mechanism responsible for the hydrolysis of phospholipid in bile fistula rats is not obvious. A novel enzyme with phospholipase Aj activity has been demonstrated in the rat intestine [94]. This enzyme has its highest specificity for phosphatidyl glycerol and its role for the hydrolysis of dietary PC is unclear. 

After platelet phospholipid labelling by traces of C]-arachidonic... 

At 30 min there were not great differences of the inhibitory action of X-537A in the presence of various cation concentrations. In total phospholipid labeling a similar trend of changes was seen (Table 4). 

Clements et al. (50) provided indirect evidence that surface-active material from the alveoli may reach the large airways. They showed that when phospholipid-labeled liposomes were deposited in rabbit alveoli, about 1% reached the trachea, whereas 50-60% remained in the lung. 

Further investigations were carried out at lipid double layers and at phospholipids of membranes. Lipid-lipid and lipid-protein interactions were recognized by diazirine labeling (79PNA2595). 

Figure 51-2. Diagrammatic representation (not to scale) of the binding of factors Va, Xa, Ca +, and prothrombin to the plasma membrane of the activated platelet. The sites of cleavage of prothrombin by factor Xa are indicated by two arrows. The part of prothrombin destined to form thrombin is labeled prethrombin.The Ca " is bound to anionic phospholipids of the plasma membrane of the activated platelet.

A further partihon system based on the use of liposomes, and commercialized under the name Transil [110, 111], has shown its utiUty as a UpophiUcity measure in PBPK modeling [112]. Fluorescent-labeled liposomes, called fluorosomes, are another means of measuring the rate of penetration of small molecules into membrane bilayers [113, 120]. Similarly, a colorimetric assay amenable to HTS for evaluating membrane interactions and penetrahon has been presented [116]. The platform comprises vesicles of phospholipids and the chromahc Upid-mimehc polydiacetylene. The polymer undergoes visible concentrahon-dependent red-blue transformahons induced through interactions of the vesicles with the studied molecules. 

A planar BLM cannot be investigated by means of the molecular spectroscopical methods because of the small amount of substance in an individual BLM. This disadvantage is removed for liposomes as they can form quite concentrated suspensions. For example, in the application of electron spin resonance (ESR) a spin-labelled phospholipid is incorporated into the liposome membrane this substance can be a phospholipid with, for example, a 2,2,6,6-tetramethylpiperidyl-A-oxide (TEMPO) group ... 

Rachel, K., Asuncionpunzalan, E. and London, E. (1995) Anchoring of tryptophan and tyrosine analogs at the hydrocarbon polar boundary in model membrane-vesicles - paralax analysis of fluorescence quenching induced by nitroxide-labelled phospholipids. Biochemistry 34,15475-15479. 

Hendrickson, H. S., Hendrickson, E. K., Johnson, I. D. and Farber, S. A. (1999). Intramolecularly quenched BODIPY-labeled phospholipid analogs in phospholipase A(2) and platelet-activating factor acetylhydrolase assays and in vivo fluorescence imaging. Anal. Biochem. 276, 27-35. 

Gaffney, B.J. and McConnell, H.M. 1974. The paramagnetic resonance spectra of spin labels in phospholipid membranes. Journal of Magnetic Resonance 16 1-28. 

Hubbell, W.L. and McConnell, H.M. 1971. Molecular motion in spin-labeled phospholipids and membranes. Journal of the American Chemical Society 93 314—326. 

DCIA has been used to label numerous proteins and other biomolecules, including phospholipids (Silvius et al., 1987), to study the interaction of mRNA with the 30S ribosomal subunit (Czworkowski et al., 1991), in the investigation of cellular thiol components by flow cytometry (Durand and Olive, 1983), in the detection of carboxylate compounds using peroxyoxalate chemiluminescence (Grayeski and DeVasto, 1987), and for general sulfhydryl labeling (Sippel, 1981). 

Abstract To understand how membrane-active peptides (MAPs) function in vivo, it is essential to obtain structural information about them in their membrane-bound state. Most biophysical approaches rely on the use of bilayers prepared from synthetic phospholipids, i.e. artificial model membranes. A particularly successful structural method is solid-state NMR, which makes use of macroscopically oriented lipid bilayers to study selectively isotope-labelled peptides. Native biomembranes, however, have a far more complex lipid composition and a significant non-lipidic content (protein and carbohydrate). Model membranes, therefore, are not really adequate to address questions concerning for example the selectivity of these membranolytic peptides against prokaryotic vs eukaryotic cells, their varying activities against different bacterial strains, or other related biological issues. 

The results summarized above were obtained by using fluorescence based assays employing phospholipid vesicles and fluorescent labeled lipopeptides. Recently, surface plasmon resonance (SPR) was developed as new a technique for the study of membrane association of lipidated peptides. Thus, artificial membranes on the surface of biosensors offered new tools for the study of lipopeptides. In SPR (surface plasmon resonance) systemsI713bl changes of the refractive index (RI) in the proximity of the sensor layer are monitored. In a commercial BIAcore system1341 the resonance signal is proportional to the mass of macromolecules bound to the membrane and allows analysis with a time resolution of seconds. Vesicles of defined size distribution were prepared from mixtures of lipids and biotinylated lipopeptides by extruder technique and fused with a alkane thiol surface of a hydrophobic SPR sensor. 

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