References: Lecithin
J Pharm Sci. 1993 Mar;82(3):273-5.
Synthesis of galactose derivatives that render lectin-induced agglutinating ability to liposomes.
Yoshioka H, Ohmura T, Hasegawa M, Hirota S, Makino M, Kamiya M.
Department of Environmental Science, School of Pharmaceutical Science, University of Shizuoka, Japan.
Three galactose (Gal) derivatives, Gal beta 1-n-C16H33 (1), Gal beta (1-4)-Glc beta 1-n-C16H33 (2), and Gal beta 1-(CH2CH2O)3-n-C16H33 (3), were synthesized and incorporated into liposomes prepared from egg yolk lecithin. Agglutination of these liposomes with Ricinus communis agglutinin was examined by following the change of turbidity. Liposomes containing 3 were effectively agglutinated in contrast to the cases of 1 and 2, suggesting that the oxyethylene groups act as a favorable spacer to extrude Gal groups into the water. Differential scanning calorimetry showed that 3 was mixed with egg yolk lecithin at room temperature, but 1 and 2 were in the gel state, resulting in the phase separation that makes the recognition of Gal residue with Ricinus communis agglutinin difficult.
Laxative online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8450421&dopt=Abstract lecithin
Biochemistry. 1995 May 30;34(21):7264-70.
Cholesterol transfer from low density lipoproteins to reconstituted high density lipoproteins is determined by the properties and concentrations of both particles.
Bottum K, Jonas A.
Department of Biochemistry, College of Medicine, University of Illinois at Urbana-Champaign 61801, USA.
Cholesterol spontaneously transfers from low density lipoproteins (LDL) to high density lipoproteins (HDL). This transfer is important physiologically as it supplies the major portion of cholesterol for the lecithin:cholesterol acyltransferase reaction and is one mechanism for the reduction of atherogenic LDL cholesterol. The objective of this work was to examine the properties of both HDL and LDL which modulate cholesterol transfer, as well as to obtain the relevant kinetic constants for the transfer at concentrations of lipoproteins approaching those existing in vivo. To examine the effects of HDL structural parameters on cholesterol transfer, we prepared reconstituted HDL particles with saturated or unsaturated phospholipid, with apolipoprotein AI or apolipoprotein AII, with increasing size and phospholipid content, and with increasing initial contents of cholesterol. We also prepared five LDL subfractions of variable density and size. The kinetics of cholesterol mass transfer were measured by incubating LDL with rHDL at 37 degrees C, separating the lipoproteins by dextran sulfate/Mg2+ precipitation of LDL at timed intervals, and analyzing rHDL cholesterol content. The cholesterol content of rHDL at equilibrium, Ceq, and the half-time for transfer, t1/2, as well as the ratio of the lipid surface areas of LDL to rHDL were used in the analysis of the kinetic data by the aqueous diffusion model for lipid transfer developed by Nichols and Pagano [(1982) Biochemistry 21, 1720-1726]. The only variables that significantly affect the C(eq) and/or t1/2 are the phospholipid content and composition of the rHDL and the size or density of the LDL particles.(ABSTRACT TRUNCATED AT
Biochim Biophys Acta. 1993 Mar 14;1146(2):247-57.
Curvature dependent induction of the interdigitated gel phase in DPPC vesicles.
Boni LT, Minchey SR, Perkins WR, Ahl PL, Slater JL, Tate MW, Gruner SM, Janoff AS.
Liposome Company, Inc., Princeton, NJ.
Ethanol causes biphasic melting behavior in saturated lecithins (Rowe (1983) Biochemistry 22, 3299-3305), a consequence of the formation of the stable interdigitated phase (Simon, S.A. and McIntosh, T.J. (1984) Biochim. Biophys. Acta 773, 169-172). The membrane systems studied to date have been large vesicle systems in which the membrane surface can be assumed to be locally planar. An immediate question arises as to whether surfaces of higher curvature interdigitate. To address this question we have prepared DPPC vesicles of varying diameters which we employed to determine the limiting size at which interdigitation occurs using ethanol as the inducer. We find that with decreasing vesicle size the concentration of ethanol necessary for the onset of interdigitation increases. Small isolated vesicles, at inducing concentrations of ethanol, do not stably interdigitate but rupture and coalesce into a viscous gel comprised of interdigitated lipid sheets. As discussed elsewhere (Ahl et al. (1992) Biophys. J. 243a) these sheets can be used as precursors for producing liposomes of large size and high internal volumes useful in drug delivery or modeling applications.
Laxative online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8452859&dopt=Abstract lecithin
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