Cholesterol derivative

Figure 42-2. Chemical diversity of hormones. A. Cholesterol derivatives. B. Tyrosine derivatives. C. Peptides of various sizes D. Glycoproteins (TSH, FSH, LH) with common a subunits and unique P subunits.

Several studies have investigated whether statins possess pharmacologic properties in addition to their LDL cholesterollowering effect that may confer additional benefits in IHD.24 These studies were prompted by evidence that patients with normal LDL cholesterol derived benefit from statins. Statins have been shown to modulate the following characteristics thought to stabilize atherosclerotic plaques and contribute to the cardiovascular risk reduction seen with these drugs ... 

Certain azacrown-appended cholesterol derivatives can form unique vesicular or lamellar structures in the absence and the presence of metal salts in aqueous solution.187-190 These superstructures created from the azacrown-appended cholesterol derivatives are useful as a template for the transcription into the silica structure. Azacrown-appended cholesterol gelator creates the novel multilayered spherical structure in acetic acid, whereas this gelator results in the fluffy globular aggregates in the presence of Pd(N03)2.191... 

Whole egg and egg yolk HMDS Hexadecanenitrile, octadecanenitrile, cholesterol derivatives (TMS derivative) 28, 29, 30... 

Xu H, Wang KQ, Deng YH, da Chen W (2010) Effects of cleavable PEG-cholesterol derivatives on the accelerated blood clearance of PEGylated liposomes. Biomaterials 31 4757-4763... 

Because total cholesterol is composed of cholesterol derived from LDL, VLDL, and HDL, determination of HDL is useful when total plasma cholesterol is elevated. HDL may be elevated by moderate alcohol ingestion (fewer than two drinks per day), physical exercise, smoking cessation, weight loss, oral contraceptives, phenytoin, and terbutaline. HDL may be lowered by smoking, obesity, a sedentary lifestyle, and drugs such as /1-blockers. 

Reinitzer discovered liquid crystallinity in 1888 the so-called fourth state of matter.4 Liquid crystalline molecules combine the properties of mobility of liquids and orientational order of crystals. This phenomenon results from the anisotropy in the molecules from which the liquid crystals are built. Different factors may govern this anisotropy, for example, the presence of polar and apolar parts in the molecule, the fact that it contains flexible and rigid parts, or often a combination of both. Liquid crystals may be thermotropic, being a state of matter in between the solid and the liquid phase, or they may be lyotropic, that is, ordering induced by the solvent. In the latter case the solvent usually solvates a certain part of the molecule while the other part of the molecule helps induce aggregation, leading to mesoscopic assemblies. The first thermotropic mesophase discovered was a chiral nematic or cholesteric phase (N )4 named after the fact that it was observed in a cholesterol derivative. In hindsight, one can conclude that this was not the simplest mesophase possible. In fact, this mesophase is chiral, since the molecules are ordered in... 

Various novel imprinting techniques have also been presented recently. For instance, latex particles surfaces were imprinted with a cholesterol derivative in a core-shell emulsion polymerization. This was performed in a two-step procedure starting with polymerizing DVB over a polystyrene core followed by a second polymerization with a vinyl surfactant and a surfactant/cholesterol-hybrid molecule as monomer and template, respectively. The submicrometer particles did bind cholesterol in a mixture of 2-propanol (60%) and water [134]. Also new is a technique for the orientated immobilization of templates on silica surfaces [ 135]. Molecular imprinting was performed in this case by generating a polymer covering the silica as well as templates. This step was followed by the dissolution of the silica support with hydrofluoric acid. Theophylline selective MIP were obtained. 

Nakamura and Matsui [71] prepared silica nanotubes as a spin-off product of sol-gel synthesis wherein tetraethylorthosilicate (TEOS) was hydrolyzed in the presence of ammonia and D, L-tartaric acid. Ono et al. [72] showed that certain cholesterol derivatives can gelate tetraethyl orthosilicate (TEOS) to obtain tubular silica structures. Using cholesterol based gelators nanotubes of transition metal (Ti, V and Ta) oxides can also be prepared. The organogelators used in these processes are chiral diamino... 

E. Uptake of cholesterol-derived bile salts in the intestine... 

Inhibitors of HMG-CoA reductase activity (for example compac-tin240), or compounds that lower the levels of the enzyme (including a number of oxygenated cholesterol derivatives,241- 24 la such as 25-liy-droxycholesterol), not only decrease the formation of polyprenyl diphosphate, but also affect the formation of cholesterol and the polyprenyl side-chains of coenzyme Q. Consequently, prolonged treatment with such compounds may cause side effects, for example, changes in membrane fluidity (see also, Section III,5), decreased activity of membrane enzymes,1214,2,3 and inactivation of membrane transport systems,246 and, therefore, indirectly prevent glvcosvlation of proteins. 

The association of amphiphiles is strongly solvent-, temperature-, pH- and concentration-dependent. The studies of various aggregates formed by a cholesterol derivative 91 [31 ] illustrate this point (Figure 4.11). The dissociation and reassembling of tobacco mosaic virus into its constituent parts discussed in Section 5.2.1 provides an elegant example of a more complicated assembly... 

Originality While liquid-crystal cholesterol derivatives are reported in the literature,... 

Goldfinger (4) proposed preparing an alkoxy(meth)acrylate cholesterol derivative, (III), as a liquid-crystal composition. 

Much of the cholesterol synthesis in vertebrates takes place in the liver. A small fraction of the cholesterol made there is incorporated into the membranes of he-patocytes, but most of it is exported in one of three forms biliary cholesterol, bile acids, or cholesteryl esters. Bile acids and their salts are relatively hydrophilic cholesterol derivatives that are synthesized in the liver and aid in lipid digestion (see Fig. 17-1). Cholesteryl esters are formed in the liver through the action of acyl-CoA-cholesterol acyl transferase (ACAT). This enzyme catalyzes the transfer of a fatty acid from coenzyme A to the hydroxyl group of cholesterol (Fig. 21-38), converting the cholesterol to a more hydrophobic form. Cholesteryl esters are transported in secreted lipoprotein particles to other tissues that use cholesterol, or they are stored in the liver. 

Osada, K., Ravandi, A., and Kuksis, A. 1999. Rapid analysis of oxidized cholesterol derivatives by high-performance liquid chromatography combined with diode-array ultraviolet and evaporative laser light-scattering detection. J. Am. Oil Chem. Soc. 76 863-871. 

Formation of cholesterol and some of its derivatives. All of the carbon atoms of cholesterol are derived from acetyl-CoA by way of mevalonate in a pathway with 33 reaction steps. From cholesterol a wide variety of steroids and bile acids and bile salts are formed. Many of the reactions leading to cholesterol derivatives are organ-... 

Fig. 6 Reciprocal optical pitch as a function of dopant content. Host material is a cholesterol derivative used in the enhanced chirality in N with bent-core molecules [5]...

Impairment of bile acid absorption and consequent loss of these acids via excretion presumably causes an increase in hepatic conversion of cholesterol to bile acids. This conversion lowers serum cholesterol, particularly when serum contains high levels of cholesterol derived from dietary intake. However, when fed with a cholesterol-free diet, 10% pectin supplementation stimulated a 3-fold increase in cholesterol biosynthesis (77). Biosynthesis of phospholipids and triglycerides also increased significantly hence, it was suggested that these increases occurred in response to diminished fat absorption occasioned by pectin intake. This compensatory biosynthesis of cholesterol and lipids may account for pectin s inability (in most cases) to lower serum cholesterol levels in animals fed cholesterol-free diets. 

Other cholesterol derivatives include cholesteryl-3 /3-oxy-succinamido-ethylenedi-methylamine (product 1 in Figure 15.6) and cholesteryl-3 /3-carboxyamidoethylene-dimethylamine (product 2 in Figure 15.6)... 

Vitamin D. Vitamin D is a steroidlike hormone that can be obtained from dietary sources or synthesized in the skin from cholesterol derivatives in the presence of ultraviolet light. Vitamin D produces several metabolites that are important in bone mineral homeostasis.27,31 In general, vitamin D derivatives such as 1,25 dihydroxyvitamin D3 increase serum calcium and phosphate levels by increasing intestinal calcium and phosphate absorption and by decreasing renal calcium and phosphate excretion.27,46... 

Takeuchi K, Ishihara M, Kawaura C et al (1996) Effect of zeta potential of cationic liposomes containing cationic cholesterol derivatives on gene transfection. FEBS Lett... 

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