Cholesterol chemical structure

Why are some organic compounds colored while others aren t /3-Carotene, the pigment in carrots, is purple-orange, for instance, while cholesterol is colorless. The answer involves both the chemical structures of colored molecules and the way we perceive light. 

HMR 3339, a newly designed molecule that binds to human recombinant ER and shows selective agonistic and antagonistic activity in vitro and in vivo, rapidly decreased cholesterol and LDL in a dose-dependent manner (Vogelvang et al. 2004). It seems, therefore, that the decrease in non-HDL cholesterol is a hepatic effect quite accessible to compounds that, despite differences in chemical structure, are capable of exerting some type of SERM activity. 

After the first successful attempts in 1928 to identify the active biochemicals found in antibacterial molds, followed the rediscovery of penicillin by Fleming, identification of its chemical structure by Hodgkin, and subsequent synthesis by Chain, Heatley, and Florey, which led to the commercial production of penicillin in the mid 1940s [1], Since then, other families of (3-lactam antibiotics have been developed [2, 3], and their massive use worldwide continues to be a forefront line of action against infectious pathogens [4-6]. In recent years, (3-lactams have found other biomedical applications, such as inhibitors of serine protease ([7, 8] for a review, see [9]) and inhibitors of acyl-CoA cholesterol acyltransferasa (ACAT) [10]. Encouraged by their bioactivity, the synthesis and chemistry of (3-lactam antibiotics have been the focus of active research, and chemical modification of some basic structures available from biosynthesis (semisynthetic approaches) as well as the discovery of fully chemical routes to de novo synthesis of (3-lactam... 

Figure 15.25 Chemical structure of mannose containing cationic cholesterol lipid.

Fig. 7 (a) A comparison of the TE of DOTAP/DOPC/Chol-DNA complexes (black squares) and DOTAP/DOPC/PC-cholesterol-DNA complexes (gray bowties). The replacement of DOPC with PC-cholesterol, which has a similarly hydrated headgroup, fails to increase TE. (b) The chemical structures of cholesterol and PC-cholesterol. Reprinted with permission from [27]. Copyright 2009 American Chemical Society... 

Figure 9.15 Chemical structures of some of the important sterols used as biomarkers in estuaries (e.g., /3-sistosterol, stigmasterol, campesterol, brassicasterol, and cholesterol).

Figure 10.2 Chemical structures of common plant sterols and cholesterol.

Cholesterol is a major hpid component of mammahan cell plasma membranes, accounting for approximately 35% of the total lipid of the membrane. Cholesterol has a chemical structure that is very different from the major polar hpid constiments, which is a consequence of the fused ring system of cholesterol that gives this hpid less conformational flexibihty than the straight chains of the polar lipids. It is thus not surprising that cholesterol does not mix well in membranes and that cholesterol segregates as crystals at around 50-60 mol% in bilayers of several lipids and at a much lower mol fraction of cholesterol in bilayers comprising hpids with unsaturated acyl chains (5). 

The chemical structure of phytosterols is similar to that of cholesterol so that these compounds may be involved in oxidative reactions. Przybylski and Eskin (42) found some oxidation products formed from plant sterols during storage of fried food products. Similar oxidation products were found in soybean oil and wheat flour (43). In light of health concerns associated with cholesterol oxidation products, potential health risks of phytosterol oxidation products are now receiving serious attention. 

Fats and fat-like compounds of varying chemical structures are classified as lipids. They have a low molecular weight and are insoluble in water. The original substance in fat biosynthesis is acetyl-CoA (so-called activated acetic acid). On the basis of chemical criteria, they may be divided into simple lipids (glycerides, cholesterol, cholesterol esters, bile acids) and complex lipids, (s. tab. 3.7)... 

Saturated fatty acids chemical structure, 639 dietary, 320,362-363 LDL cholesterol and, 364 Scavenger receptor A, 360,635 S cells, 65... 

The chemical structures of the lipid studied are shown in the Fig. 1. There are two different types of behavior for monolayers from those lipid mixtures (i) solid film formation with relatively low pressure of a collapse (cholesterol rich monolayers) and (ii) viscous elastic film formation, when the concentration of CHL is less 30% in the monolayer. The character of the behavior of a monolayer is quite similar upon replacing of CHL by Q3P, though the LB film morphology is essentially different. 

None of the venoms, however, showed any interaction with films of cholesterol or protein, nor did hydrolysis occur in films of tripalmitin, triolein, cerebron, or sphingomyelin. The reaction with lecithin is highly specific. Not only is it sensitive to the chemical structure of the film, but the reaction rate may also be greatly altered by slight changes in the orientation of the molecules in the film or by changes in the pH of the solution or of the concentration of venom. 

Once the benefits of a key component in food are documented, the challenge is to increase its concentration, and presumably its benefits, while maintaining safety. For example, isoflavones in soy are phytoestrogens with a chemical structure similar to estrogen. Isoflavones may reduce cholesterol, but what is the risk of increasing the intake of a compound that may modulate estrogens Knowledge of the toxicity of functional food components is crucial to improve their benefit-risk ratio. The efforts... 

These plant sterols have similar chemical structures to cholesterol (Figure 6.6) and the capacity to lower plasma cholesterol and LDL cholesterol. The higher the dietary intake of plant sterols from the diet, the lower the serum cholesterol level. 

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