Anhydrous cholesterol, crystals

Figure 3 Comparison of the densities (in g/cm ) of model compounds for membrane lipids computed from constant-pressure MD simulations with the coiTespondmg experimental values. The model compounds include solid octane and tricosane, liquid butane, octane, tetradecane, and eico-sane, and the glycerylphosphorylcholme, cyclopentylphosphorylcholme monohydrate, dilauroly-glycerol, anhydrous cholesterol, cholesterol monohydrate, and cholesterol acetate crystals. (Models from Refs. 18, 42, and 43).

A very typical zeolitic organic material is anhydrous cholesterol. Its crystals are penetrated by channels along the three crystallographic directions a, b, and c (Fig. 2.1.45). It is therefore a good reagent for gas-solid and solid-solid reactions. This has already been verified by quantitative reactions with bromine [1] and oxalic add [1]. 

In crystals of both cholesterol monohydrate (Craven, 1976) and anhydrous cholesterol (Shieh et al, 1977) the cholesterol molecules are organized into bilayers with the molecular axes approximately but not... 

Bile contains three amphiphiles (cholesterol, lecithin and bile salts) assembled in mixed micelles. These greatly increase water-solubility of cholesterol (usually very low about 70-80 nM). If excess cholesterol is present, the solubilizing capacity of the micelles is exceeded and supersaturation reached nucleation of cholesterol molecules can occur with formation of cholesterol mono-hydrate crystals and stones[8]. Only ChM is found in gallstones and its dissolution rate is slower than anhydrous cholesterol[9]. 

Cover 0.5 g of cholesterol with 5 mL of acetic acid in a small Erlenmeyer flask, swirl, and note that the initially thin slurry soon sets to a stiff paste of the molecular compound C27H45OH CH3CO2H. Add 1 mL of acetic anhydride and heat the mixture on the steam bath for any convenient period of time from 15 min to 1 h record the actual heating period. While the reaction takes place, prepare the chromatographic column. Cool, add 20 mL of water, and extract with two 25-mL portions of ether. Wash the combined ethereal extracts twice with 15-mL portions of water and once with 25 mL of 10% sodium hydroxide, dry by shaking the ether extracts with 25 mL of saturated sodium chloride solution, then dry the ether over anhydrous sodium sulfate for 10 min in an Erlenmeyer flask, filter, and evaporate the ether. Save a few crystals of this material for TLC (thin-layer chromatography) analysis. Dissolve the residue in 3-4 mL of ether, transfer the solution with a capillary dropping tube onto a column of 12.5 g of silica gel, and rinse the flask with another small portion of ether. ... 

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