Lipid categories

Figure 4.8 Schematic comparison of intrasource separation of lipid categories to the theoretical electrophoretic separation of lipid classes, (a) Schematically shows the selective ionization of different lipid categories under three different experimental conditions with or without adding a small amount of LiOH. (b) Schematically shows the imaginary chromatograms of lipid classes after electrophoretic analyses under corresponding experimental conditions. PC, TAG, FA, PE, and AL stand for phosphatidylcholine, triacylglyceride, nonesterified fatty acid, phosphatidylethanolamine, and anionic lipids, respectively. Christie and Han [lb]. Reproduced with permission of Elsevier.

Taken together, interpretation of lipidomics data should not only extensively consider different pathways within a network of an individual lipid category but also expand the influence from other categories of lipids (i.e., consider the interrelationship between the networks). In order to do well on this, it is always important to conduct comprehensive analysis of cellular lipidomes, including individual molecular species and regioisomers. 

A number of comprehensive volumes have been published, dealing with the structure, occurrence, chemistry, and biochemistry of lipids [16—20]. In this section, the main lipid categories are introduced only... 

The classical PTPs can be subdivided into receptorlike PTPs and nonreceptor, cytosolic PTPs. The second category of PTPs are broadly defined as dual specificity phosphatases (DSPs), which dephosphorylate pSer/ pThr as well as pTyr. MAP kinase phosphatases (MKPs) ( MAP kinase cascades) and PTEN are examples of DSP family members. Remarkably, PTEN also has lipid phosphatase activity that is specific for phosphatidylinositol-3,4,5-trisphosphate generated in response to the actions of PI3K. Finally, the class of low molecular mass (LM-) PTPs and that of CDC25 PTPs accomplish the cells repertoire of PTPs (Fig. 3). 

The results showed that the compounds studied with more frequency in the aquatic environment, and of which, logically, there is more information, are the antibiotics, analgesics and anti-inflammatories (like diclofenac, ibuprofen, naproxen, acetylsalicylic acid, and paracetamol), as well as the p-blocker atenolol. In the category of antibiotics, several families are included, like the macrolides (erythromycin), the fluoroquinolones (ofloxacin and ciprofloxacin), sulfonamides (sulfamethoxazole), penicillins (amoxicillin), the metronidazol, and trimethoprim. Other therapeutic groups also widely studied and frequently found in the environmental waters are the lipid regulators (gemfibrozil and bezafibrat), antiepileptic carbamaze-pine, and antidepressants (diazepam, fluoxetine, paroxetine) (see Table 3). 

We have also determined the delivery sites of alkylbenzenes by NMR. As already described in Section III.A, PrBe are deeply transported to the chain tail region in the bilayer core and the delivery site can be classified into category III [46]. Benzene, however, cannot deeply penetrate into the hydrophobic core, zone III, but is trapped preferentially at the interfacial site of the bilayer, zone II the delivery site can be classified into category II. Although benzene is generally considered to be hydrophobic, the delivery site of benzene determined by NMR is reasonable in the sense of the 7r-electrons with some affinity for the hydrophilic sites of the bilayer. Both drug and lipid sides of the H NMR spectra show that alkylbenzenes can deeply penetrate into the bilayer interior in the order PrBe > ethylbenzene > toluene > benzene, which is consistent with the sequence of the insolubility in water. 

Basic concepts and the methods for determining DD sites in lipid bilayer membranes have been developed by NMR on the atomic site level. Lipid bilayer interfaces as delivery sites can be specified by taking advantage of the site selectivity of NMR. DD sites can be generally classified into the three categories in Fig. 6. The distinction is based on the difference in the micropolarity in membranes around the drug. It has been briefly mentioned how to evaluate dynamic properties of drugs in membranes. 

Major determinants of membrane fluidity may be grouped within two categories [53] (1) intrinsic determinants, i.e., those quantifying the membrane composition and phase behavior, and (2) extrinsic determinants, i.e., environmental factors (Table 1). In general, any manipulation that induces an increase in the molal volume of the lipids, e.g., increase in temperature or increase in the fraction of unsaturated acyl chains, will lead to an increase in membrane fluidity. In addition, several intrinsic and extrinsic factors presented in Table 1 determine the temperature at which the lipid molecules undergo a transition from the gel state to liquid crystalline state, a transition associated with a large increase in bilayer fluidity. 

Of the three major categories of nutrients, lipids are the slowest to be digested and absorbed. Furthermore, these processes take place only in the... 

Primary or genetic lipoprotein disorders are classified into six categories for the phenotypic description of dyslipidemia. The types and corresponding lipoprotein elevations include the following I (chylomicrons), Ha (LDL), lib (LDL + very low density lipoprotein, or VLDL), III (intermediate-density lipoprotein), IV (VLDL), and V (VLDL + chylomicrons). Secondary forms of hyperlipidemia also exist, and several drug classes may elevate lipid levels... 

Greiff [3.25] classified the virus into five categories 1, Nucleic acid type (either DNA-core or RNA-core) 2, sensitivity against lipid solvents 3, envelope about the nucleocapsid or not (naked) 4, pH sensitivity, exposure to pH 3 for 30 min differentiates between those viruses, which lose more than a decade in titer and those which lose no titer or less than one decade 5, heat-sensitive virus cannot be exposed to +50 °C for 30 min. 

The one and only distinctive feature of lipids is that they are all totally hydrophobic (water fearing), or nearly so. They generally will not chemically interact with water and therefore will not dissolve in water. Chemically, lipids fit into several categories, each of which is structurally unique. Common types of lipids include triacylglycerols, phospholipids, and steroids. 

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