Critical micelle concentration contract

The conformations of tethered polyethylene glycol (PEG) chains anchored on styrene polymers (PS) latex particles, labelled with pyrene and mononaphthyl PEG ester, in the presence of an anionic surfactant, dodecyl sulphate (SDS), and Na and K chlorides were studied, using distance-dependent nonradiative energy transfer from the naphthalene moieties to the pyrene ones as a guide. The results indicated a change in acceptor/donor separation distance in response to external stimuli. Analysis of the resnlts snggested considerable polymer chain contraction on interaction with salts and surfactant below the critical micelle concentration of the surfactant. 

Table 1. Critical Micelle Concentration(cmc) of phenothiazines and minimum phenothiazine concentration to contract the HA gel(cc)...

The critical micelle contraction values were obtained using the conductance method from the usual equivalent conductance vs. the square root of concentration plots. The apparatus has been described before (21). About 20 experimental points were obtained for each cmc determination. No cmc could be detected above 20 wt % of acetone and 30 wt % of n-propanol. Surfactants were studied in water - - acetone mixtures at 298.15 K in water + n-propanol mixtures at 308.15 K for comparison purposes with other systems (12) (see the Discussion section). 

In response to a meal, cholecystokinin is released from the intestine and causes relaxation of the sphincter of Oddi and contraction of the gallbladder (see Chapter 48). This allows a concentrated solution of micelles (consisting of bile salts, lecithin, and cholesterol) to enter the intestine. In the intestinal lumen, dietary cholesterol and the products of triglyceride digestion (predominantly free fatty acids and monoglycerides) are incorporated into mixed micelles. Micelles deliver lipolytic products to the mucosal surface. To carry out these functions, a critical micellar bile acid concentration of 2ramoI/L is necessary. 

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