Phospholipids anionic

Tandem mass spectrometry also allows the determination of isomers and diastereoiso-mers. As an example, glycosylmonophosphopolyisoprenols [38,39] display in the negative ion FAB mode abundant (M — H) ions. When these ions are fragmented under low-energy collisions, an abundant fragment corresponding to the phospholipid anion is observed,... 

From a study of several compounds, it appears that a 2-hydroxyl trans to the phosphate strongly favours the formation of the phospholipid anion. The ribose derivative differs from the arabinose derivative only by the trans configuration of the 2-hydroxy group with respect to the phosphate. 

FIGURE 6-15 Schematic representation of the ion permeability modulation for cation-responsive voltammetric sensors based on negatively charged lipid membranes. Complexation of the guest cation to the phospholipid receptors causes an increase of the permeability for the anionic marker ion. (Reproduced with permission from reference 49.)... 

A large number of combinations are theoretically possible and a lot of these structures are actually used in practice. We know that nature makes use of this variety, e.g., to form cell membranes by phospholipids. However, in daily practice the pool of hydrophobic raw material for the production of anionic phosphorus-containing surfactants is survey able. 

Niehaus, W.J., Jr (1978). A proposed role of superoxide anion as a biological nucleophile in the deesterification of phospholipid. Bioorganic Chemistry, 7, 77-84. 

The activation of prothrombin, like that of factor X, occurs on the surface of activated platelets and requires the assembly of a prothrombinase complex, consisting of platelet anionic phospholipids, Ca, factor Va, factor Xa, and prothrombin. 

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.

Activated platelets, besides forming a platelet aggregate, are required, via newly expressed anionic phospholipids on the membrane surface, for acceleration of the activation of factors X and II in the coagulation cascade (Figure 51—1). 

ECF. Note that phosphorus is the major anion within the cells. Given this distribution, serum phosphate concentration does not accurately reflect total body phosphorus stores. Phosphorus is expressed in milligrams (mg) or millimoles (mmol), not as milliequivalents (mEq). Because phosphorus is the source of phosphate for adenosine triphosphate (ATP) and phospholipid synthesis, manifestations of phosphorus imbalance are variable. 

In both Navanax neurons (65) and an artificial phospholipid bilayer membrane (66). salicylic acid (1-30 mM) increased K" " permeability but decreased Cl- permeability resulting in a net Increase in membrane conductance. To account for the selective effect of salicylic acid (and other benzoic acids) on the two permeabilities, it was proposed that the anions of the organic acids adsorb to membranes to produce either a negative surface potential (66) or an increase in the anionic field strength of the membrane (47, 48). 

Fig. 2. Generation of tenase and prothrombin complexes. PPL represents the anionic phospholipid surface provided by the platelets (platelet phospholipid). Cleavage of prothrombin by the prothrombinase complex results in the formation of thrombin and the release of a small fragment called prothrombin fragment 1.2 (PFI.2).

Ryeom, SW, Silverstein, RL, Scotto, A, and Sparrow, JR, 1996a. Binding of anionic phospholipids to retinal pigment epithelium may be mediated by the scavenger receptor CD36. J Biol Chem 271, 20536-20539. 

T. Ohyashiki, M. Nunomura, and T. Katoh, Detection of superoxide anion radical in phospholipid liposomal membrane by fluorescence quenching method using 1,3-diphenylisobenzofuran. Biochim. Biophys. Acta. 1421, 131-139 (1999). 

Over the years, various tissues and tissue components have been discussed as compartments into which drugs can penetrate and bind. The ability of lipophilic drugs to partition into membranes has been known for many years, especially cationic drugs that can bind to anionic phospholipid membranes [15-20]. The phenomenon of lysosomal trapping has also been cited as a factor that contributes to the tissue binding and high VD values of weakly basic drugs [20-23]. 

The studies on phospholipid bilayers with defined amounts of charged component are helpful to explain the partition characteristics in biological membranes. Liposome water partition data of propranolol in lipids from kidney epithelial cells (a common model system in pharmaceutical sciences for the uptake into the gastrointestinal tract) have been successfully described with partition models developed for pure bilayers or defined mixtures [159]. Since lipophilic cations and anions can be used as probes for the membrane potential, their interaction with microbial and mitochondrial membranes has been studied... 

Scherer, P. G. and Seelig, J. (1989). Electric charge effects on phospholipid head-groups. Phosphatidylcholine in mixtures with cationic and anionic amphiphiles, Biochem., 28, 7720-7728. 

Conformational changes in BmorPBP were also studied in the presence of model membranes using CD spectroscopy. Conformational changes more pronounced than those observed at low pH were detected in the presence of anionic vesicles of dimyristoylphosphatidylglycerol (DMPG), whereas the effect of neutral phospholipids vesicles, dimyristoylphosphatidylcholine (DMPC) was... 

Rourke, A.M., Y. Cha, and D. Collins. 1996. Stabilization of granulocyte colony-stimulating factor and structurally analogous growth factors by anionic phospholipids. Biochemistry 35 11913-11917. 

---