Micelle marker

In MACE, the alteration of the ionic mobility as a factor of the tenside concentration in the background electrolyte solution is a measure of the strength of interaction, which may be evaluated graphically. In Fig. 1, a schematic representation of MEKC is given for the separation of micelle and EOF markers as well as drug solutes of different lipophilicity. If the substances are neutral, their position between the EOF marker and the micelle marker is given only by their lipophilicity, which controls their affinity to the micellar phase. This means that S3 in Fig. 1 has the lowest hydrophilicity. 

Fig. 1 Schematic representation of the separation principle of MEKC. An EOF/ micelle marker and three solutes differing in lipophilicity in the presence of anionic micelles in the background buffer are present. The lipophilicity increases in the sequence Sj < S2 < S3 t—migration time of EOF (nonionic solutes) S (solute) me —micelle.

Particle separation can be characterized by the separation factor, Rp, which is the ratio of eluant to particle elution volumes, or, by the difference in elution voliame, AV, between particle and eluant marker turbidity peaks. For polystyrene monodisperse standards, a linear relationship occ irs between the log of the particle diameter and AV, with a series of parallel lines resulting for different concentration of either salt or surfactant below its critical micelle concentration (IT>18,19) The separation factor has also been shown to be independent of eluant... 

The order parameter values calculated from the data of Fig. 4 are illustrated in Fig. 5. The data there suggest the existence of two continuous transitions, one at a = 0.85 and another at a = 0.7. The first transition at a = 0.85, denoted by the arrow labeled a in Fig. 5, is assigned to the formation of percolating clusters and aggregates of reverse micelles. The onset of electrical percolation and the onset of water proton self-diffusion increase at this same value of a (0.85) as illustrated in Figs. 2 and 3, respectively, are qualitative markers for this transition. This order parameter allows one to quantify how much water is in these percolating clusters. As a decreases from 0.85 to 0.7, this quantity increases to about 2-3% of the water. 

KP and v can, in contrast to kp, not be determined via the concentration gradient for binary and ternary mixed micelles, because for the calculation of the Nemstian distribution a constant CMC and an almost constant partial molar volume must be assumed. The calculation of aggregation constants of simple bile salt systems based on Eq. (4) yields similar results (Fig. 8b). Assuming the formation of several concurrent complexes, a brutto stability constant can be calculated. For each application of any tenside, suitable markers have to be found. The completeness of dissolution in the micellar phase is, among other parameters, dependent on the pH value and the ionic strength of the counterions. Therefore, the displacement method should be used, which is not dependent on the chemical solubilization properties of markers. For electrophoretic MACE studies, it is advantageous for the micellar constitution (structure of micelle, type of phase micellar or lamellar) to be known for the relevant range of concentrations (surfactant, lipids). 

Gatti, C.A., Risso, P.H., and Zerpa, S.M. 1998. Study of the inhibitory effect of hydrophobic fluorescent markers on the enzyme coagulation of bovine casein micelles Action ofTNS. Food Hydmcol. 12 393-400. 

Figure 3. Physicochemical features of mixed aggregates of phosphatidylcholine, phosphatidylethanolamine (PE, used as surface marker), and gangliosides (Gut, G ,a, GTlb, Gt),b) at increasing proportions of ganglioside. Highest value of the outer PE/total PE ratio corresponds to liposomes. Lowering of turbidity and concurrent enhancement of ratio indicate presence of micelles. Break point is indicated as the transition ganglioside/ phospholipid molar ratio. ...

While it might seem reasonable to use a generic marker such as polyethylene glycol, which is completely eliminated without absorption (used to verify integrity of the epithelial barrier), it is important for the marker to have physical properties similar to the nutrient in question because of the complexity of the postprandial intestinal milieu - a thick slurry of mixed micelles, oil and water phases, and suspended particles. The marker should partition among the phases similarly to the analyte of interest and should have similar intestinal transit times. Thus, sugars must be used to trace sugars, sterols to trace sterols, etc. 

To calculate the capacity factor, it is necessary to know the migration time not only of the analyte but also of the micelle and the EOF. Although there is no ideal marker in MECC, a very hydrophobic molecule, such as Sudan III, will spend most of its time partitioned in the micellar phase and... 

Figure 26-5. Principle of the 13C-mixed triglyceride breath test. Absorption of 13C-mixed triglycerides requires prior hydrolysis by pancreatic lipase (1), which leads to production of free fatty acids (stearic acid) and monoacylglycerol [2-(l-13C)octanoylglycerol]. These metabolites are incorporated into micelles, absorbed, and transported to the liver (2). Further degradation by hepatic enzymes and P-oxidation results in formation of 13C02, which is absorbed into the bloodstream, transported to the lung, and exhaled (3). Thus, exhalation of 13C02 reflects intestinal lipolysis and is a marker of pancreatic exocrine function.

In one of our earlier applications, FCS diagnosed unanticipated micelle formation and led to the first development of confocal image microscopy for smaller focal volumes [3]. Recognizing the effective applications of fluorescent marker d mamics to understand cell membrane d mamics, we applied FCS to molecular diffusion on cell membranes, entering thereby into a long series of studies of the dynamics of membrane processes in life, which was at that time a quagmire of conflicting ideas [4]. Later, we also extended FCS theory to fluid flow analysis [9]. It has proven useful for a diversity of ultrafast chemical kinetics as well, c.f. [10-13]. 

To check the pH-sensitivity, biotin-containing micelles are formulated by mixing mPEG -HZ-PE (60% mol), PEG gg-PE (37% mol), Rhodamine-PE (0.5% mol, fluorescent marker), and biotin-PE (2.5% mol, biotin component) in chloroform. 

IVLE should be used in patients with liver failure only to prevent essential fatty acid deficiency when initial serum triglyceride concentrations exceed 300 mg/dL. If serum triglyceride concentrations are low or normal, IVLE should be used as a calorie source. Monitoring serum triglyceride concentration and FFA oxidation (not available in all facilities) to ensure that lipid is both cleared and oxidized appropriately has been suggested. Triglyceride concentrations are the only available marker in most clinical practices at this time. Oral MCTs have been used occasionally with success because they do not require pancreatic enzymes or micelle formation before absorption. However, these products do not provide essential fatty acids. 

Recent physical-chemical observations on native mammalian systems reveal that the proposed mixed micellar mechanism of lipid solubilization and transport in both bile and in upper small intestinal contents is incomplete [1,260-263]. Bile is predominantly a mixed micellar solution but, particularly when supersaturated with Ch, also contains small liquid-crystalline vesicles which, as suggested from model systems [239], are another vehicle for Ch and L transport. In dog bile which is markedly unsaturated with Ch [258], these vesicles exist in dilute concentrations and may be markers of the detergent properties of BS on the cells lining the biliary tree and/or related to the mode of bile formation at the level of the canaliculus. In human hepatic bile, which is generally dilute and markedly supersaturated with Ch, these vesicles may be the predominant form of Ch and L solubilization and transport [261]. If hepatic bile is extremely dilute, it is theoretically possible that no BS-L-Ch micelles may be present [268] all of the lipid content may be aggregated... 

---