Assay of cholesterol

In the enzymatic assays of cholesterol, glucose, and urea, oxygen is used and H2O2 is formed. The reaction for uric acid [69-93-2] is... 

Theory The assay of cholesterol is solely based on the fact that practically all 3 (3-hydroxysterols e.g., cholesterol, readily produces an insoluble molecular addition complex with pure digitonin (1 1)—a steroidal saponin isolated from either Digitalis purpurea or Digitalis lanata. The complex thus obtained is crystalline in nature, fairly stable and possesses very low solubilities. 

Structure of quinoneimine chromogen formed in the assay of cholesterol. 

E403 von Schenck, H., Treichl, L., Tilling, B. and Olsson, A.G. (1987). Laboratory and field evaluation of three desktop instruments for assay of cholesterol and triglyceride. Clin. Chem. 33, 1230-1232. 

R136 Brandford, S., Sobecki, S. and Bais, R. (1989). Whole-blood quality-control material for Reflotron assays of cholesterol. Clin. Chem. 35, 1255-1256. 

Cholesterol is the most abundant steroid in man, occurring both as free cholesterol (about 30%) and esterified with fatty acids (about 70%). The assay of cholesterol is of great importance in the diagnosis of disturbances in lipid metabolism. The normal concentration range in blood serum is 3.1-6.7 mmol/1 (Strassner, 1980). Cholesterol determination is also of importance in fermentation control and the pharmaceutical industry. 

In a similar manner, but with no necessity to add an electron acceptor, an assay of cholesterol has been designed using an organic metal electrode of NMP+TCNQ (Wollenberger, 1984). HRP was adsorbed on this material and covered by nylon-bound COD. The electrode was polarized at +25 mV to obtain a signal upon addition of cholesterol. The working stability of this sensor was poor. 

Chiang, J.Y. (1991). Reversed-phase high-performance liquid chromatography assay of cholesterol 7 alpha-hydroxylase. Meth. Enzymol. 206, 483 91. 

Another method to preserve the 3D cell morphology and chemical arrangement to submicron precision is by freeze-fracture of frozen-hydrated cells directly within the confines of the mass spectrometer. There is considerable evidence that the presence of water as well as preserving the native bilayer structure provides an optimal environment for ionization [63-65].This method has been employed in many studies with SIMS such as the quantitative assay of cholesterol in macrophage cells [66] and the observation of lipid rearrangement in... 

A. Isolation and Determination of Lipids and Higher Fatty Acids. B. Preparation and itnalysis of Phospholipids and Derivatives. C. Fractionation Procedures for Higher and Lower Fatty Acids. D. Preparation and Assay of Cholesterol and Ergosterol. 

Mattiasson B.O., Danielsson B. and Mosbach K. (1976) Enzyme thermistor assay of cholesterol, glucose, lactose and uric acid in standard solutions as well as in biological samples. Anal. Letters, 9, 217-234. 

Dry chemistry tests are used for the assay of metaboHtes by concentration or by activity in a biological matrix. In general, reactive components are present in amounts in excess of the analyte being deterrnined to make sure that the reactions go to completion quickly. Other enzymes or reagents are used to drive the reactions in the desired direction (25). Glucose and cholesterol are the analytes most commonly measured. 

In this context, the discussion shall be restricted to the colorimetric assays of urea (BUN), bilirubin and cholesterol. However, the clinical significance of these substances and the extent to which they are present in biological fluids besides the various drugs that usually interfere with their assay are also described adequately in the following pages ... 

How would you carry out the assay of bilirubin or cholesterol by colorimetric method Explain. 

Part—I has three chapters that exclusively deal with General Aspects of pharmaceutical analysis. Chapter 1 focuses on the pharmaceutical chemicals and their respective purity and management. Critical information with regard to description of the finished product, sampling procedures, bioavailability, identification tests, physical constants and miscellaneous characteristics, such as ash values, loss on drying, clarity and color of solution, specific tests, limit tests of metallic and non-metallic impurities, limits of moisture content, volatile and non-volatile matter and lastly residue on ignition have also been dealt with. Each section provides adequate procedural details supported by ample typical examples from the Official Compendia. Chapter 2 embraces the theory and technique of quantitative analysis with specific emphasis on volumetric analysis, volumetric apparatus, their specifications, standardization and utility. It also includes biomedical analytical chemistry, colorimetric assays, theory and assay of biochemicals, such as urea, bilirubin, cholesterol and enzymatic assays, such as alkaline phosphatase, lactate dehydrogenase, salient features of radioimmunoassay and automated methods of chemical analysis. Chapter 3 provides special emphasis on errors in pharmaceutical analysis and their statistical validation. The first aspect is related to errors in pharmaceutical analysis and embodies classification of errors, accuracy, precision and makes... 

Arora S, Beaudry C, Bisanz KM et al (2010) A high-content RNAi-screening assay to identify modulators of cholesterol accumulation in Niemann-Pick type C cells. Assay Drug Dev Technol 8 295-320... 

In summary, based on the observation of divergent in vitro and in vivo SAR, a new class of cholesterol-lowering compounds was discovered. Subsequent biological characterization of the first generation lead compound SCH-48461, limited the site of action to be at or near the intestinal villi, with the most probable mechanism being the inhibition of luminal absorption. An SAR optimization based solely on an in vivo assay and without biochemical characterization of the molecular target led to the design of ezetimibe (1). 

Monobactams have been investigated as p-lactamase inhibitors <98CHE1308, 98CHE1319>. The ketene-imine route to P-lactams was used to obtain 1,3,4-trisubstituted derivatives with high trans selectivity. The enolate from 4-hydroxy-y-lactone reacted with the imine (Ar CH NAr ) to give 59, vdiich cyclized in the presence of lithium chloride at low temperature to yield 60. The compounds were assayed for cholesterol absorption inhibition and 61 (R = = OH, R = F) was found to be a potent inhibitor of 3-hydroxy-3-... 

Assays to determine the activities of enzymes defective in any one of the six known disorders of cholesterol biosynthesis have only been described for sterol-delta7-reductase... 

Assays for the determination of cholesterol in routine clinical laboratories include cholesterol esterase and thus quantify total cholesterol (i.e., unesterified and es-terified cholesterol). However, specific assays are also available that lack cholesterol esterase and hence allow the determination of unesterified or free cholesterol. The difference between total and unesterified cholesterol gives the concentration of cholesterol esters. 

Dobiasova M, Frohlich JJ (1998) Assays of lecithin cholesterol acyltransferase (LCAT) Methods Mol Biol 110 217-230... 

Before an immobilized enzyme can be used for an industrial process, it is essential to characterize it in terms of its catalytic and kinetic properties. A quantitative assay must be developed to measure the activity, kinetic parameters, and stability of the enzyme. In a coupling reaction, H202 rapidly reacts with phenol and 4-aminoantipyrine (electron donor) in the presence of peroxidase to produce a quinoneimine chromogen (Equation E12.2, Figure El 1.2), which is intensely colored with a maximum absorbance at 510 nm. (This is the same as the product formed in the analysis of cholesterol in Experiment 11.)... 

The intermediate, NAD- or NADP-, is a radical on the nicotinamide that can react with [(bpy)3Ru]3+. Any enzyme that produces or consumes either NADH or NADPH can be directly monitored by ECL since only the reduced forms NAD(P)H but not the oxidized forms NAD(P)+ can function as a coreactant [31,49], This difference has been exploited in the clinical chemistry assays of ethanol, glucose, bicarbonate, cholesterol, and glucose-6-phosphate dehydrogenase. 

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