Sterol lipids

Proteins, glucosides, lipids, sterols, and so on, although generally very water soluble, are nonetheless frequently able to impart considerable stability to emulsions (and... 

A mechanism Is proposed by which water-insoluble plant lipids (sterols etc.) may act as allelochemicals via micelle formation with long-chain fatty acids. By this process plant lipid solubility and transport In the aqueous medium are enhanced. This might suggest a reevaluation of water-insoluble plant constituents such as sterols as potential allelopathic agents. 

Schrick, K., Nguyen, D., Karlowski, W. M., and Mayer, K. F. 2004. START lipid/sterol-binding domains are amplified in plants and are predominantly associated with homeodomain transcription factors. Genome Biol., 5(6) R41. 

The example of a total extract composition of a tropical soil from the Amazon, Brazil, shows mycose as the major compound, numerous other monosaccharides, lipid components such as fatty acids and fatty alcohols, and natural product biomarkers (Fig. 9a). The mycose and elevated levels of the other saccharides reflect the efficient fungal/microbial degradation of plant detritus in the tropics. This can be compared to the saccharides in the soil from an almond orchard in California, where glucose and mycose are the main sugars with lipids, sterols and triterpenoids (Fig. 9b, ). 

Mechanism of Action. Amphotericin B appears to work by binding to specific steroidlike lipids (sterols) located in the cell membrane of susceptible fungi.7 This binding causes increased permeability in the cell membrane, leading to a leaky membrane and loss of cellular components. 

The influence of native vegetation on the composition of SOM was studied in well-dated volcanic soils at the Mount Etna region, Sicily, Italy. Whole soil samples were taken under chestnut and oak stands, and their humic acids (Baglieri et al., 2007) and nonfractionated whole soil samples were analyzed by Py-FIMS. The proportions of compound classes in Table 14.4 show that the roughly 2000-year-old soil under an oak stand was significantly richer in lipids, sterols, and free fatty acids than was the soil under chestnut. In another pair of soil samples with a longer period of soil formation (about 7000-9000 years), the difference between oak and chestnut was +4.2% for lipids, +2.6% for sterols and +2.5% for free fatty acids (not shown). This predominance of aliphatics in the soils under oak confirms Nierop et al. (2003), who also found the release of aliphatics from oak stands into soil by conventional lipid extractions and GC/MS. 

During recent decades, the use of artificial phospholipid membranes as a model for biological membranes has become the subject of intensive research. As discussed above, biological membranes are composed of complex mixtures of lipids, sterols, and proteins. Defined artificial membranes may therefore serve as simple models of membranes that have many striking similarities with biological membranes. A comparison of some important physicochemical properties of biological and artificial membranes is given in Table 1.8 [2]. 

Amphotericin B is highly lipophilic (Figure 29.14) and interacts with membrane lipid sterols, such as cholesterol, to disrupt membrane permeability. Because amphotericin is freely filtered, it achieves high concentrations in distal tubular fluid and easily forms complexes with cholesterol and other lipids present in distal tubular luminal membranes. Amphotericin effectively transforms the tight distal tubular epithelium into an epithelium leaky to water, H+ and K+. Functional abnormalities observed with amphotericin B are attenuated when the antifungal agent is administered as an emulsion formulation whereby amphotericin is incorporated into lipid... 

The effect of cholesterol on the thermotropic phase behavior of PC bilayer also varies significantly with the structure, particularly the degree of unsaturation, of the hydrocarbon chains, with more highly unsaturated PCs exhibiting a reduced miscibility with cholesterol and other sterols. Moreover, the structure of the lipid polar headgroup is also important in determining the effect of cholesterol on the host lipid, as is the structure of the sterol molecule itself. For more information on the application of DSC to the biologically important area of lipid-sterol interactions, the reader is referred to recent reviews (23-25). 

Fig. 1. Graphical representation of discriminant function D1 derived from the che-mometric analysis of mass spectral signatures of 30 microlayer and bulk seawater film extracts (FI). Intensities at each m/z represent the loadings for that particular m/z variable used to calculate the D1 discriminant function score. Prominent m/z variables include those representative of fatty acids, acyl lipids, sterols, poloxy-mers and humic compounds...

Papers impregnated with kieselguhr, aluminum oxide, silica gel, and calcium carbonate are also commercially available from Schleicher and Schiill and Whatman. These adsorbent-loaded papers have been used to separate moderate and low polarity substances such as lipids, sterols, steroids, insecticides and pigments [16]. They function generally in a manner similar to thin layers of the same adsorbent, but, in some cases, the presence of cellulose along with the adsorbent can provide unique separations [17,18]. Applications of adsorbent paper chromatography have been reviewed [19]. 

Morris, R.J. and Culkin, F., 1977. Marine lipids sterols. Oceanogr. Mar. Biol. Annu. Rev.,... 

Natural rubber latex is a colloid, the dispersed phase being predominantly rubber and the dispersion medium water. Fresh latex has a specific gravity of 0.96-0.98 and a pH in the range of 6.5-7.0. In addition to rubber and water, latex contains small quantities of proteins, resins including fats, fatty acids, other lipids, sterol and sterol esters, carbohydrates, and mineral matter. Fresh latex is composed of rubber (30-40%), proteins (1-1.5%), resins (1.5-3%), mineral matter (0.7-0.9%), carbohydrates (0.8-1%), and water (55-60%). 

The ABC transporter superfamily consists of a variety of transmembrane proteins, many of them responsible for the transport of diverse classes of substrates that include not only anticancer drug molecules but also lipids, sterols, polypeptides, ions, and metabolic products across extracellular and... 

High density lipoproteins (HDL) are the predominant class of hemolymph lipoproteins in marine invertebrates. Very low density and low density lipoproteins are absent. These HDL are characterized by high molecular peptide(s) and phosphatidyl choline as the predominant lipid. Sterol esters are absent or in trace amounts. 

The r61e of nutrients in inducing feeding is indicated by the presence of sugar and amino acid receptors. Receptor cells for lipids (sterols, phospholipids) have not yet been identified despite their rdle in nutrition (Beck and Schoonhoven, 1980 House, 1974) and host plant selection (Stddler and Hanson, 1976,1978). This is probably the result of the methodology (see Section 1.3) and not a general lack of sensitivity of contact chemoreceptors. 

Molybdophosphorle acid for reducing compounds, lipids, sterols and steroids. 

The study of monolayers of amphiphilic compounds at the water-air interface has spanned many decades. Much of the early work on monolayers has been summarized in the monograph by Gaines. The early work on monolayers that elucidated the basic thermodynamic behavior of single-chain amphiphiles, lipids, sterols, and other molecules set a... 

Fried, B., Holender, E. S., Shetty, P. H., and Sherma, J. (1990). Effects of Echinostoma trivolvis (Trematoda) infection on neutral lipids, sterols, and carotenoids in Heli-soma trivolvis (Gastropoda). Comp. Biochem. Physiol. 97B 601-604. 

Pazoutova, S., Kfen, V., feezanka, T., Amler, E., Elieger, M., Rylko, V. and Sajdl, P. (1989) Effect of triadimefon on lipids, sterols and membrane fluidity in submerged cultures of Claviceps purpurea. Pestic. Biochem. Physiol., 34,211-217. 

Jones, RJ. and Kubow, S., Lipids, sterols, and their metabolites, in Modem Nutrition in Health and Disease, Shils, M.E., Oson, J.A., Shike, M., and Ross, A.C., Eds., Lippincott Williams Wilkins, Baltimore, MD, 1999, pp. 67-94. 

In Chapter 3, we introduced the concept of the surfactant and discussed how molecules with hydrophobic and hydrophilic sections will self-assemble into lyotropic phases in aqueous solution. The stability of a specific phase depends on molecular shape and concentration in the solvent. In the discussions that follow, we focus on the phase behavior of a simplified model membrane containing only lipids, even though the real cell membrane consists of a complex mbcture of many different varieties of lipids, sterols, and membrane proteins. Figure 6.3 shows molecular structures for some common lipid molecules found in the cell membrane. For a detailed description of the cell membrane, I recommend The Structure of Biological Membranes as further reading. ... 

Jones PJH and Kubow S (1999) Lipids, sterols and their metabolism. In Shils ME, Olson JA, Shike M, and Ross AC (eds.) Modem Nutrition in Flealth and Disease, 9th edn., pp. 67-94. Baltimore Williams Wilkins. 

Associated with phospholipids, sterols constitute a significant proportion of the membrane lipids. Sterols of both unicellular and multicellular algae have been described in detail by Patterson (1991), whose 40-page review remains an unparalleled source of reference in this field. The diatoms produce more than ten sterols including three - cholesterol, methylene-24-cholesterol, and methyl-25-cholesta-5,22-dienol - that are often in the majority. As diatoms constitute one of most important links in the food chain, it is usual to find these sterols in the tissues of many filter feeders, mostly shellfish and particularly oysters, which do not synthesize sterols de novo. 

Drazen, J.C., PWeger, C.F., Guest, M.A., and Nichols, P.D. (2008) Lipid, sterols and fatty add composition of abyssal holofhurians and ophiuroids from the North-East Padfic Ocean food-web implications. Comp. Biochem. Physiol., 151B, 79-87. 

Mannock, D.A., Lewis, R.N.A.H., McMullen, T.P.W., and McElhaney, R.N. (2010) The effect of variations in phospholipid and sterol structure on the nature of lipid-sterol interactions in lipid bilayer model membranes. Chem. Phys. Lipids, 163, 403—448. 

In the previous discussion it was suggested that membrane integration of intrinsic proteins could be facilitated by the interaction of hydrophobic regions of the nascent peptides with the phospholipids of the bilayer. Although it is assumed that the basic structure of the bilayer is the same for all membranes, the lipid compositions of various membranes show significant differences, both with respect to the relative proportions of the various phospholipids and their fatty substituents. In addition, some membranes may contain special types of lipids (sterols, sulfolipids, cardiolipin, etc.) that are absent in other membranes. It is also conceivable that there may exist regional differences in lipid composition within a single membrane. 

The physical properties of the membrane, which are strongly influenced by the lipid composition, seem to be important in so far as they are regulated in the face of environmental changes (diet, temperature, etc.) by subtle changes in the proportions of amphiphilic lipids, sterols and fatty acids. Such changes in physical properties may modulate the activities of membrane... 

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