Amino-phospholipids

Achve translocation of phospholipids aaoss the plasma membrane has been demonstrated both from the inner to the outer leaflet and from the outer to the inner leaflet. The translocation processes specifically transport phosphatidyserine and phosphatidylethanolamine from the cytoplasmic to the outer surface of the membrane while choline phosphatides are transported from the outer to the cytoplasmic surface. The rate of translocahon, in general, is greater for the amino phospholipids compared with the choline phospholipids. 

The maintenance of an asymmetric distribution of phospholipids across the plasma membrane with choline phospholipids predominating on the external surface and amino phospholipids confined to the cytoplasmic leaflet of the membrane has now been well estabhshed. The participation of... 

Tilley, L., Cribier, S., Roelofsen, B., Op den Kamp, J.A.F. and van Deenen, F.F.M., 1986, ATP-dependent translocation of amino phospholipids across the human erythrocyte membrane. FEES Lett., 194 21-27. 

Matthees, D. P, Precolumn derivatization of amino phospholipids for LC, Five. S. D. Acad. 

All membranes which have been examined so far show very different lipid (and protein) compositions for their two leaflets. A common feature of mammalian cell membranes is that the amino-phospholipids and phosphatidylinositol are concentrated in the cytosolic leaflet (Figure 6.13). In contrast, sphingolipids are highly concentrated in the external leaflet of the plasma membrane. In the bacterial example also shown in Figure 6.13 phosphatidylinositol is concentrated on the cytoplasmic face, but in the castor bean glyoxysomal membrane, whereas phosphatidylethanolamine was mainly in the outer (cytoplasmic) leaflet, the accessible phosphatidylinositol was mainly in the opposite leaflet. This latter example emphasizes two points - first that generalizations should not be made from system to system without firm evidence and, second, that the distribution calculated... 

Other Reactions of Phospholipids. The unsaturated fatty acid groups in soybean lecithin can be halogenated. Acetic anhydride combined with the amino group of phosphatidylethanolamine forms acetylated compounds. PhosphoHpids form addition compounds with salts of heavy metals. Phosphatidylethanolamine and phosphatidjhnositol have affinities for calcium and magnesium ions that are related to interaction with their polar groups. 

A 0-9% salt solution is considered to be isotonic with blood. Other electrolytes present include bicarbonate ions (HCOj ) and small amounts of potassium, calcium, magnesium, phosphate, sulphate and organic acid ions. Included among the complex compounds and present in smaller amounts are phospholipids, cholesterols, natural fats, proteins, glucose and amino acids. Under normal conditions the extracellular body fluid is slightly alkaline with a pH of 7-4. ... 

Phospholipids are important constituents of cell membranes and are of two kinds. Glycerophospholipids, such as phosphatidylcholine and phos-phatidylethanolamine, are closely related to fats in that they have a glycerol backbone esterified to two fatty acids (one saturated and one unsaturaled) and to one phosphate ester. Sphingomyelins have the amino alcohol sphingo-sine for their backbone. 

The choline-containing phospholipids, PC and Sph, predominate in the outer leaflet and the amino-containing phospholipids (PE and PS) in the inner leaflet. 

The amino acid sequences for glycophorins A and A (see Refs. 8 and 19) are presented in Fig. 1. It may be clearly seen that residues 1-70 of these glycoproteins extend into the cell exterior. The hydrophobic portion of the glycoprotein, residues 71-92, appear to be imbedded in the phospholipid membrane, and residues 93-131 protrude into the cell cytoplasm. ... 

In addition to phenolic substances, there are other components present in foods which have no antioxidant activity of their own, but which increase that of phenolic antioxidants. They are called synergists, and they should be accounted for in any discussion of antioxidant activity. Polyvalent organic acids, amino acids, phospholipids (lecithin) and various chelating agents belong to this group. Proteins may modify the efficiency of antioxidants as they react with the reaction products of both antioxidants and synergists. 

Positive components in meat are free amino acids and phospholipids, which are active both in lard and in edible oils (Nasner, 1985). The ethanol-... 

Koryta et al. [48] first stressed the relevance of adsorbed phospholipid monolayers at the ITIES for clarification of biological membrane phenomena. Girault and Schiffrin [49] first attempted to characterize quantitatively the monolayers of phosphatidylcholine and phos-phatidylethanolamine at the ideally polarized water-1,2-dichloroethane interface with electrocapillary measurements. The results obtained indicate the importance of the surface pH in the ionization of the amino group of phosphatidylethanolamine. Kakiuchi et al. [50] used the video-image method to study the conditions for obtaining electrocapillary curves of the dilauroylphosphatidylcholine monolayer formed on the ideally polarized water-nitrobenzene interface. This phospholipid was found to lower markedly the surface tension by forming a stable monolayer when the interface was polarized so that the aqueous phase had a negative potential with respect to the nitrobenzene phase [50,51] (cf. Fig. 5). 

Therefore, it is currently believed that anandamide is formed from membrane phospholipids (Fig. 4) through a pathway that involves (1) a trans-acylation of the amino group of phosphatidylethanolamine with arachidonate from the sn-1 position of phosphatidylcholine and (2) a D-type phosphodiesterase activity on the resulting A-arachidonylphosphati-dylethanolamide (NAPE). Synthesis of anandamide is presumably regulated at the levels of both enzymes, the A-acyltranferase and the phospholipase D, by stimuli that raise intracellular calcium or by receptors linked with cAMP and PKA. It has been shown that anandamide is formed when neurons are depolarized and, therefore, the intracellular calcium ion levels are elevated (Cadas, 1996). 

Using liposomes made from phospholipids as models of membrane barriers, Chakrabarti and Deamer [417] characterized the permeabilities of several amino acids and simple ions. Phosphate, sodium and potassium ions displayed effective permeabilities 0.1-1.0 x 10 12 cm/s. Hydrophilic amino acids permeated membranes with coefficients 5.1-5.7 x 10 12 cm/s. More lipophilic amino acids indicated values of 250 -10 x 10-12 cm/s. The investigators proposed that the extremely low permeability rates observed for the polar molecules must be controlled by bilayer fluctuations and transient defects, rather than normal partitioning behavior and Born energy barriers. More recently, similar magnitude values of permeabilities were measured for a series of enkephalin peptides [418]. 

Biochemical tests are usually performed after pure cultures have been obtained. The standard indole, methyl red, Voges-Proskauer, citrate, and litmus milk tests may be used to show important physiological characteristics. To study the functional diversity of bacteria, the utilization of carbohydrates, amines, amides, carboxylic acids, amino acids, polymers, and other carbon and nitrogen sources can be tested.28 Dilution-based most-probable number (MPN) techniques with phospholipid fatty acids as biomarkers have been employed for studying different bacterial species in lakes.40 The patterns of antibiotic resistance in bacteria isolated from natural waters have been useful for identifying sources of water pollution.34... 

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