Phospholipids types

Other materials have also been studied for their ability to reduce protein adsorption onto surfaces. Because many cell membranes are based on phospholipids, polymers containing phospholipid-type head groups have been utilized for this purpose. Poly(2-methacroylethyl phosphoryl choline) could be plasma deposited onto silicone rubber and the adhesion of albumin reduced by factors of up to 80 (Fig. 

Phospholipid type compounds have been synthesized through a reaction sequence based on the hydrolytic cleavage of the P-N bond in B-rm—butyl-l, 3,2-oxazaphospholidines. ... 

Figure U-6 NMR-spectra for macroscopic polymorphic phases of phospholipids in bilayers, hexagonal Hn and isotropic phases (small vesicles, micelles, inverted micelles and cubic phases). Similar spectra are recorded for any one phase regardless of which phospholipid type forms the phase because the chemical shift differences for different phospholipids is smaller (2-4 ppm) than the anisotropy of chemical shift ( 30-50 ppm) (reproduced from [63] with permission from Elsevier Science, Amsterdam, The Netherlands).

For 40-50 years, phosphate esters occnpied the role of relatively small-volume anionic surfactants. They have been unable to effectively compete economically and possessed lesser surface activity than sulfates. Consequently, they have primarily been nsed in indnstrial, household, industrial, and institutional (HI I), and agricultural applications. The recent advance in processes for high MAPs and the development of phospholipid-type molecnles have provided prodncts with increased surface activity, mildness, and superior skin compatibility. Conseqnently, interest is beginning to develop in the personal care indnstry. 

Levin [150] and Gaber and Peticolas [151] have shown that the upper shift and broadening occurs also in biomembrane materials. Such a shift has been used by Gaber and Peticolas to monitor the lateral interactions in phospholipids. We notice that for these phospholipid-type material the long-chain alkyl residues are fixed at one end to polar head groups and thus cannot perform rigid librational motions about their axes. Forcefully they can only perfonn libro-twisting or libro-torsional motions. 

The use of phospholipids to mimic cell walls has been one commercially successful coating strategy. To create a polymer surface with phospholipid-type properties, two routes are possible. The polymer surface can be modified by the attachment of the biological molecule of interest, as described in the modification of polymer surfaces with phosphorylcholine (72-74), amphiphilic molecules (75) or liposomes. Alternatively, phosphorylcholine moieties have been incorporated into artificial surfaces by using polymerizable precursors the most representative monomer is 2-methacryloxyethylphosphorylcholine (MFC) 16, 17). Block copolymers of phosphorylcholine with other hydrophobic comonomers like lauryl methacrylate (75) also have been found to be effective. 

The primary phospholipids of plants are PC, PE, PI, PG, BPG, and PS. While the general composition of these phospholipids remains the same for a specific plant tissue, there have been reports of modifications as a response to certain conditions. For example water stress, temperature stress, hormones, etc. have been reported to lead to modifications In phospholipid composition or phospholipid turnover rates. These studies have referred to changes In both the headgroup and the fatty acid composition of the phospholipids. These two portions of the molecule may be altered Independently, but It also Is possible to modify the fatty acid content of a particular phospholipid type by modifying the headgroup. For example ... 

Therefore, headgroup additions or modifications could lead to changes In both the concentration of a phospholipid type and also to specific species within that type ... 

A notable feature of the lipid regions of biological membranes is that the different phospholipid types may be asymmetrically distributed across the bilayer. For the erythrocyte membrane for example, it has been demonstrated by surface labelling and phospholipase digestion that the sphingomyelin and phosphatidylcholine are located in the outer half of the bilayer, whereas the phosphatidylethanolamine and phosphatidylserine are localized to the inner half (Zwaal et al., 1973). 

The effect is more than just a matter of pH. As shown in Fig. XV-14, phospholipid monolayers can be expanded at low pH values by the presence of phosphotungstate ions [123], which disrupt the stmctival order in the lipid film [124]. Uranyl ions, by contrast, contract the low-pH expanded phase presumably because of a type of counterion condensation [123]. These effects caution against using these ions as stains in electron microscopy. Clearly the nature of the counterion is very important. It is dramatically so with fatty acids that form an insoluble salt with the ion here quite low concentrations (10 M) of divalent ions lead to the formation of the metal salt unless the pH is quite low. Such films are much more condensed than the fatty-acid monolayers themselves [125-127]. 

Fatty acids normally occur naturally as esters fats oils phospholipids and waxes all are unique types of fatty acid esters There is however an important class of fatty acid derivatives that exists and carries out its biological role m the form of the free acid This class of fatty acid derivatives is described m the following section... 

Phosphatidic acids not only are intennediates in the biosynthesis of triacylglycerols but also are biosynthetic precursors of other members of a group of compounds called phosphoglycerides or glycerol phosphatides. Phosphorus-containing derivatives of lipids are known as phospholipids, and phosphoglycerides are one type of phospholipid. 

Thomson Click Organic Interactive to learn to identify common phospholipids by their charge and type. 

The second type of material includes spores, which may or may not produce disease symptoms but which can germinate in the insect gut and give rise to vegetative bacterial cells which in turn may produce, and exoenzymes such as phospholipases (lecithinases) or hyaluronidase. The phospholipases may produce direct toxic symptoms owing to their action on nervous or other phospholipid-containing tissue. Hyaluronidase breaks down hyaluronic acid and produces effects on animal tissue which are morphologically similar to the breakdown of insect gut wall in the presence of microbial insecticide preparations. 

Lipid phosphate phosphohydrolases (LPPs), formerly called type 2 phosphatidate phosphohydrolases (PAP-2), catalyse the dephosphorylation of bioactive phospholipids (phosphatidic acid, ceramide-1-phosphate) and lysophospholipids (lysophosphatidic acid, sphingosine-1-phosphate). The substrate selectivity of individual LPPs is broad in contrast to the related sphingosine-1-phosphate phosphatase. LPPs are characterized by a lack of requirement for Mg2+ and insensitivity to N-ethylmaleimide. Three subtypes (LPP-1, LPP-2, LPP-3) have been identified in mammals. These enzymes have six putative transmembrane domains and three highly conserved domains that are characteristic of a phosphatase superfamily. Whether LPPs cleave extracellular mediators or rather have an influence on intracellular lipid phosphate concentrations is still a matter of debate. 

FIGURE 9.1 Examples of different types of surfaees, interfaees, and mierostruetures. (1) A biologieal membrane eomposed of phospholipid moleeules in whieh protein moleeules are embedded. (2) An NMOS logie eireuit. (3) A seetion of ZSM-5 zeolite. 

The second type of fatty liver is usually due to a metabolic block in the production of plasma lipoproteins, thus allowing triacylglycerol to accumulate. Theoretically, the lesion may be due to (1) a block in apolipoprotein synthesis, (2) a block in the synthesis of the lipoprotein from lipid and apolipoprotein, (3) a failure in provision of phospholipids that are found in lipoproteins, or (4) a failure in the secretory mechanism itself. 

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