Phospholipids structures

Cole, M. Enke, C. Direct determination of phospholipid structures in microorganisms by fast atom bombardment triple quadropole mass spectrometry. Anal. Chem. 1991, 63,1032-1038. 

An important question arises about the effects of phospholipid composition and the function of membrane-bound enzymes. The phospholipid composition and cholesterol content in cell membranes of cultured cells can be modified, either by supplementing the medium with specific lipids or by incubation with different types of liposomes. Direct effects of phospholipid structure have been observed on the activity of the Ca2+-ATPase (due to changes in the phosphorylation and nucleotide binding domains) [37]. Evidence of a relationship between lipid structure and membrane functions also comes from studies with the insulin receptor [38]. Lipid alteration had no influence on insulin binding, but modified the kinetics of receptor autophosphorylation. 

Cochlear formulations are interesting in other ways since they offer a real prospect of being able to deliver nuclear materials through cell walls without the issues associated with the use of viable vaccines. As noted, this may be especially true because not only do the phospholipid structures pass through the phospholipid cell walls but incorporated materials are protected from the surrounding environment such as enzymes that would otherwise destroy them. 

Furnkranz A. and Leitinger N. (2004). Regulation of inflammatory responses by oxidized phospholipids structure-function relationships. Curr. Pharmaceut. Design 10 915-921. 

Koynova R, Tenchov B (2009) Cationic phospholipids - structure/transfection activity relationships. Soft Matter 5 3187-3200... 

Cholesterol - an essential component of mammalian cells - is important for the fluidity of membranes. With a single hydroxy group, cholesterol is only weakly am-phipathic. This can lead to its specific orientation within the phospholipid structure. Its influence on membrane fluidity has been studied most extensively in erythrocytes. It was found that increasing the cholesterol content restricts molecular motion in the hydrophobic portion of the membrane lipid bilayer. As the cholesterol content of membranes changes with age, this may affect drug transport and hence drug treatment. In lipid bilayers, there is an upper limit to the amount of cholesterol that can be taken up. The solubility limit has been determined by X-ray diffraction and is... 

A final example of the uniqueness of phospholipid structure and composition in cells relates to the fatty acyl (or the hydrocarbon moiety) groups of particular lipid species in cells. Again this distribution, to be illustrated below, is very constant in normal cells and yet raises the question as to why specific phospholipids have a penchant for certain fatty acyl (hydrocarbon) groups which is not exhibited by other phospholipid species in the cell. This question is clearly posed in the data shown in Table 1 -6. This is an abbreviated examination of only a few cells, but a similar profile occurs in many other cells as well. 

The extent of membrane lipid polyunsaturation is another modulator of cellular oxidative susceptibility an example is mentioned above in the NO section. This is not surprising, and it has a chemical rationale since the sites of attack of oxidizing free radical species in lipids are the double bonds in polyunsaturated phospholipid structures in membranes. Therefore, it follows,... 

Phospholipids Structure Stability and Characterization of Lipid Membranes... 

The main building blocks of most liposomal drug formulations are phospholipids. This chapter will start with an introduction of phospholipid structure and briefly... 

For the elucidation, synthesis, chemical properties, physical chemistry, composition, and analytical determination of the various individual phospholipid structures in animal and plant sources, the reader is referred to Wittcoff (4). Schneider (14) discusses the nomenclature used for phospholipids in more detail and provides compositional data on commercial lecithins (Table 14). 

Figure 2.51 shows the structure of the 16-carbon fatty acid palmitic add. In the triglyceride and phospholipid structures shown in Figure 2,32, R, R, and represent the alkane "tails" of fatty adds. The fatty acid compositions of the phospholipids and triglycerides of various foods are listed in Table 2-2-...

FIGURE 1.12 Phospholipid structures. Most biological membranes take the form of a bilayer sheet. In addition to containing phosopholipids, biological membranes contain proteins and cholesterol. Vesicles are used in biology for transporting and delivering biochemicals from the interior of the cell to the membrane, or to the extracellular fluids. (Reprinted by permission from Darnell et ah, 1990.)... 

The fatty acids play an essential role in the phospholipid structure is essential.. Sauirated fatty acids are very flexible and they can exhibit a large number of conformations due to their freedom of rotation. The minimal energy corresponds to the most stable and probable coiifonnation, which is the fully extended chain. On the other hand unsatiirated fatty acids show rigid kinks and their freedom in rotation is prohibited due to the double bonds [6],... 

Apart from the type of phospholipids the formation of phospholipid structures such as bilayers, micelles or inverted micelles are directly dependent on the degree of hydration, the hydrophobic forces on the tatty acyl chains, and the electrostatic forces that are present on the polar head group region of the bilayer. The properties of the aqueous medium (pH, ionic strength, dielectric properties) are factors that influence the type of phospholipid structures. 

Simon, G. and G. Rouser. 1967. Phospholipids of the sea anemone Quantitative distribution absence of carbon-phosphorus linkages in glycerol phospholipids structural elucidation of ceramide aminoethylphophonate. Lipids 2 55. 

Cole, M.J. Enke, C.G. Direct Determination of Phospholipid Structures in Microorganisms by Fast Atom Bombardment Triple Quadrupole Mass Spectrometry, Anal. Chem. 63(10), 1032-1038 (1991). 

Fig. 3. Molecular models for the conversion of di-DHA phosphatidyl ethanolamine or di-DPA (n-6) phosphatidylethanolamine (PE) into phosphatidylserine (PS) by base exchange catalyzed by PS synthase. Molecular models were computed by energy minimization of the phospholipid structure given the di-DHA PE structure.

For the melt method, a phospholipid/triglyceride ratio of 1 4 was found to result in the best yield of drug-free lipospheres when compared with ratios of 1 2, 1 3, and 1 6 [33], Domb [42] investigated different phospholipid/fat ratios with respect to the phospholipid content on the liposphere surface. At a phospholipid/triglyceride ratio of 1 2 to 1 4, 70 to 90% of the phospholipid was located at the liposphere surface. Increasing the phospholipid content resulted in the formation of other phospholipid structures, such as liposomes. 

Fig. 2. Structure of glycerophosphate-based lipids. The complete lipid structure shown is l,2-distearoyl-s -glycerol-3-phosphocholine or phosphatidylcholine (PC). Substitution of eholine in the box with the head groups listed below results in the other phospholipid structures. CDP-diacylglycerol has a CMP and phosphatidic acid (PA) has a hydroxyl group in place of choline (not shown). Cardiolipin (CL) is also referred to as diphos-phatidyIglycerol since it contains two PAs joined by a glycerol.

Figure 1. The structures of two phospholipids. Structure A represents a classic glycerophospholipid, POPC, and it is composed of choline, phosphate, glycerol, and two fatty acids. Structure B is an example of a sphingomyelin, and if is composed of choline, phosphate, sphingosine, and only one fatty acid.

Fig. (8). Schematic representation of the phospholipid structure, a) cylinder, b) reversed cone, c) colic...

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