Lecithins shifts

Fmctose is sweeter than sucrose at low temperatures (- S C) at higher temperatures, the reverse is tme. At 40°C, they have equal sweetness, the result of a temperature-induced shift in the percentages of a- and P-fmctose anomers. The taste of sucrose is synergistic with high intensity sweeteners (eg, sucralose and aspartame) and can be enhanced or prolonged by substances like glycerol monostearate, lecithin, and maltol (19). 

Figure 3.6 compares iso-pH permeabilities of ketoprofen at various pH values in a 2% DOPC-dodecane model (open circles) and the 20% soy lecithin with SLS in the acceptor compartment (filled circles, data in Table 3.5). In the presence of the latter negatively charged lipids (with the make-up similar to that of BBM in Table 3.1), ketoprofen is intrinsically more permeable, by a factor of 17. The UWL limit, indicated by the solid curves in low-pH solutions, and consistent with the permeability Pu 19.8 x 10-6 cm s 1 (log Pu —4.7), masks the true intrinsic permeability of the membranes, P0. However, it is possible to deduce the membrane permeability if the pKa is known. In Fig. 3.6, the bending in the dashed (calculated) curves at pH 4 corresponds to the pKa of the molecule. Due to the UWL, the point of bending is shifted to higher pH values in the solid (measured) curves. The difference between the apparent pKa (pK 5.3 for DOPC and 6.3 for soy) and the true pKa (4.12) is the same as the difference between log P0 and log Pu [23],... 

Funke H, Eckardstein A von, Pritchard PH, Karas M, Albers JJ, Assmann G (1991) A frame-shift mutation in the human apolipoprotein A-I gene causes high density lipoprotein deficiency, partial lecithin cholesterol-acyltransferase deficiency, and corneal opacities. J Clin Invest 87 371-376... 

The infrared spectrum of lecithin was affected markedly in the region of the P-O-C absorption. The peaks between 9.1 and 9.4 microns showed a continuous shift from the higher frequency to the lower frequency component as the concentration of cholesterol increased from 0 to 75 mole %. The two peaks were equal at a composition of 50 mole % (Figure 4). 

Let us consider first lipid-lipid interaction. Urry et al, showed the existence of a positive CD band at 218 m/x and a negative CD band at about 192 m/z in phosphatidyl choline and phosphatidyl ethanolamine dissolved in trifluoroethanol (86). The 192-m/z band was not characterized in detail, but the 218-m/z band is of such position and shape that the addition of lipid and protein CD bands could produce a composite CD band, and hence an ORD Cotton effect, which is red shifted. As noted by Urry, the 218-m/z CD extremum of lecithin must arise from n — 7T transitions in the fatty acid ester groups. Although the optical activities of solutions of deproteinized membrane phospholipids determined at the same concentration as in the intact membrane are negligibly small, in membranes an ordered array of lipids could greatly enhance rotation. Such an effect could yield information on the nature of lipid-lipid association. This can be tested experimentally. Halobacterium cutirubrum offers a unique system since Kates has shown that the lipids in this extreme halophile contain ether bonds rather than ester bonds (43, 44), Hence, the n — tt transition essential to the CD band at 218 m/z in phospholipids does not exist. Nevertheless, we found that the ORD... 

The European reaction to traces of GMO DNA in foods has markedly affected the uses of phospholipids in food and health applications. The consumers right to know, and ingredient users avoidance of GM products, has led to a decrease in soybean and corn lecithin usage, with a shift to the usage of soft-seed lecithins (rapeseed and sunflower) that are non-GMO. 

Finally it should not be omitted to mention the fact that the rigid sphere fullerene, Ceo, can also be dissolved in vesicle membranes . When dissolved in hexane, chloroform or 1,2-dichloroethane, a narrow, concentration-independent absorption band at 334 nm (e 52000) was produced. In vesicles (lecithin, DODAB, DHP), the fullerene adsorption becomes concentration dependent whereby band-broadening, bathochromic shifts (343-360 nm) and loss of extinction (e 10000 4000) were observed in more concentrated solutions. 50 clearly aggregates within the vesicle membranes, a step not observed in micellar solutions. 

The liver is responsible for synthesis of cholesterol, high-density lipoproteins, and very-low-density lipoproteins. The enzymes lipoprotein lipase and lecithin-cholesterol acyltransferase also are synthesized in this organ. Increased serum triglyceride and FFA concentrations are encountered in patients with hepatic failure, primarily due to the increased lipolysis. The significant insulin resistance that can be seen in cirrhosis causes a shift to lipids as a fuel source. Whereas only 35% of total calories are derived from fat in normal patients after an overnight fast, this can increase to 75% in patients with cirrhosis. Incorporation of late evening snacks in patients with liver cirrhosis may correct abnormal substrate metabolism, increase carbohydrate, and decrease fat oxidation rates. ... 

In a recent study, a dose-response relationship was found between THC and the transition temperature shift for lecithins [113]. The cholesterol content was again found to influence this effect. 

Additional applications of 13C spectroscopy have been developed in an analysis of the conformation of lecithin in vesicles (Batchelor et al., 1972). It has been demonstrated that the 13C resonances of alkanes will shift upfield 5 ppm when a 7-methyl is aligned with the methylene in a gauche configuration about the a-B bond (Cheney and Grant, 1967). This means that changes in chemical shift with temperature or other conditions can be used as a measure of the... 

Detection of an NIR band for DODAB, lecithin, and DHP solutions of [60]fullerene confirmed our earlier report, which was based on differential absorption changes in the Vis region. Interestingly, the characteristic NIR-band of Ceo " within these lipid materials reveals a blue shift with a maximum centered around 1020 nm as compared to organic solutions of [60]fullerene and aqueous Ceo/Y CD where the... 

The steeper slope for tram-flupentixol suggests that it interacts about twice as strongly with lecithin as does c/s-flupentixol (Figure 11 -20) [47], [95].This indicates a stereospecific interaction of these catamphiphiles with phospholipids. The strength of interaction of the stereoisomers with the negatively charged BBPS is more extensive than with the neutral DPPC [91], and the chemical shifts of the HI signals were different for trans- and cis-flupentixol. 

In a 1 1 molar mixture of cholesterol and lecithin the OH stretching band of cholesterol lies at 3250cm , having been shifted from 3420-3400cm in the spectrum of cholesterol alone. These workers have cited some of the evidence supporting the idea that cholesterol-lecithin interactions may be important in cellular membranes and in certain other biological systems. 

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