Cholesterol detection

A.L. Crumbliss, J.Z. Stonehuerner, R.W. Henkens, J. Zhao, and J.P. O Daly, A carrageenan hydrogel stabilized colloidal gold multi-enzyme biosensor electrode utilizing immobilized horseradish peroxidase and cholesterol oxidase/cholesterol esterase to detect cholesterol in serum and whole blood. Biosens. Bioelectron. 8, 331-337 (1993). 

Clinical measurements of total cholesterol in serum or plasma detect cholesterol esters in addition to cholesterol. Between 60 and 70% of the cholesterol transported in blood is in an esterified form, where the /3-3-OH group on the steroid skeleton is covalently linked to a naturally occurring... 

Outer layer Light yellow a Not detected Cholesterol... 

Further investigation by Kresling confirmed earlier observations that saponification of the fat gave an alcohol of high molecular weight. He was unable to detect cholesterol in the tubercle lipids. It was found that ethereal hydrogen chloride would remove the acid-fast staining lipid fraction from the bacillary cell. 

This volume of secretion is supplemented in the ductules by ca. 150 ml ductular bile, resulting in a daily production of ca. 600 ml. Bile formation is lower at night than during the day. The most important constituents of the so-called liver bile are the bile acids, phospholipids, proteins, cholesterol and bilirubin. The term bile lipids includes cholesterol, bile salts and phospholipids. The manner in which cholesterol is excreted into the gall bladder is not yet known, nor have any cholesterol-specific transport systems been detected. Cholesterol is primarily broken down into bile acids, (see above) (s. tab. 3.5)... 

Devadoss etal. (18) have developed a cholesterol oxidase modified electrode that has been used to detect cholesterol in the plasma membranes of Xenopus oocytes. A platinum electrode modified with a lipid bilayer containing cholesterol oxidase (50) is operated in the amperometric mode and placed adjacent to an oocyte (Figure 17.1.3A-B). 

In milk fat, cholesterol is associated with Hpoproteins in the milk fat globule. It is also a component of animal membranes and controls rigidity and permeabihty of the membranes. Cholesterol has interesting surface properties and can occur in Hquid crystalline forms. Plants contain sterols such as P-sitosterol [83-46-5] (4b) or stigmasterol [83-48-7] (4c). Their functions in plant metaboHsm are not yet well understood. Analysis of sterols has proven useful for detection of adulteration of edible fats (9). 

Detection and result The developed chromatogram was freed from mobile phase by drying for 10 min at 110°C, allowed to cool and immersed for 1 s in the reagent solution. The plate was evaluated as rapidly as possible while it was moist since the fluorescent background increased in intensity as the plate dried out. Cholesterol appeared as a yellow-green fluorescent zone hR 20—25). 

In situ quantitation Fluorimetric analysis was made with long-wavelength UV light (2exc = 365 nm, X(, > 430 nm). The detection limit on HPTLC plates that were analyzed in a moist state was 25 ng cholesterol per chromatogram zone (Fig. 1). 

The pink color of the cholesterol begins to fade after 5 min while the color of the bile acids deepens [2]. The visual detection limit in visible light is 1 pg for cholesterol and 2 pg per chromatogram zone for bile acids [2], Fluorimetric detection is more sensitive by a factor of 1000 ... 

Detection and result The developed chromatogram was dried in a stream of cold air, immersed in the reagent solution for 1 s and heated to 80 °C for 20 — 30 min (until optimal color development occurred). Yellow to brown-colored zones were produced on a pale yellow-colored background these were suitable for quantitative analysis. The detection limits for cholesterol hRf 20 — 25) and coprostanol 25 — 30) were a few nanograms per chromatogram zone. 

Lipid regulators are ordinarily applied drugs in clinical practice, and they are used to lower the level of cholesterol and regulate the metabolism of lipids. Clara et al. [13] detected a lipid regulator bezafibrate at concentrations up to 7.6 pg L although normally they are found at lower nanograms per liter range [8,18,21,22]. 

Lipids, e.g. sitosterol, geraniol, dolichol, squalene, cholesterol 200 C, 15 min Induced fluorescence detection limits <1 pg cholesterol. [3]... 

While the fluid mosaic model of membrane stmcture has stood up well to detailed scrutiny, additional features of membrane structure and function are constantly emerging. Two structures of particular current interest, located in surface membranes, are tipid rafts and caveolae. The former are dynamic areas of the exo-plasmic leaflet of the lipid bilayer enriched in cholesterol and sphingolipids they are involved in signal transduction and possibly other processes. Caveolae may derive from lipid rafts. Many if not all of them contain the protein caveolin-1, which may be involved in their formation from rafts. Caveolae are observable by electron microscopy as flask-shaped indentations of the cell membrane. Proteins detected in caveolae include various components of the signal-transduction system (eg, the insutin receptor and some G proteins), the folate receptor, and endothetial nitric oxide synthase (eNOS). Caveolae and lipid rafts are active areas of research, and ideas concerning them and their possible roles in various diseases are rapidly evolving. 

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