References: Lecithin
Arterioscler Thromb Vasc Biol. 1997 Sep;17(9):1637-43.
Evidence that apolipoprotein A-IMilano has reduced capacity, compared with wild-type apolipoprotein A-I, to recruit membrane cholesterol.
Bielicki JK, McCall MR, Stoltzfus LJ, Ravandi A, Kuksis A, Rubin EM, Forte TM.
Department of Molecular and Nuclear Medicine, Ernest Orlando Lawrence Berkeley National Laboratory, University of California at Berkeley 94720, USA.
Human carriers of apolipoprotein (apo) A-IMilano are heterozygous for an Arg173-->Cys substitution in the apoA-I primary sequence; despite severe reductions in HDL cholesterol concentrations, affected individuals do not develop coronary heart disease, suggesting that apoA-IMilano may possess antiatherogenic properties. As the beneficial effects of wild-type apoA-I are linked to its role in HDL cholesterol transport, we examined the capacity of apoA-IMilano to recruit cell cholesterol and activate lecithin:cholesterol acyltransferase (LCAT) (two key events in the antiatherogenic reverse cholesterol transport pathway). ApoA-IMilano and wild-type apoA-I were expressed in Chinese hamster ovary cells, and their ability to recruit membrane phospholipid and cholesterol for the assembly of nascent HDL was compared. Both clonal cell lines exhibited similar levels of apolipoprotein accumulation in serum-free medium (approximately 2 micrograms/mg cell protein per 24 hours), and 15% of each apolipoprotein was associated with membrane lipids to form nascent HDL (d = 1.063 to 1.21 g/mL). SDS-PAGE showed that a majority (66 +/- 12%) of the lipidated apoA-IMilano was in the homodimer form. Compositional analyses revealed that apoA-IMilano nascent HDL had a significantly lower (P < .001) unesterified cholesterol/phospholipid mole ratio (0.47 +/- 0.10) than wild-type apoA-I complexes (1.29 +/- 0.14), indicating that apoA-IMilano had a reduced capacity to recruit cell cholesterol. In addition to the reduced unesterified cholesterol/phospholipid ratio, apoA-IMilano nascent HDL consisted mostly of small 7.4
Arch Biochem Biophys. 1995 Sep 10;322(1):135-42.
ATP synthesis by purified ATP-synthase from beef heart mitochondria after coreconstitution with bacteriorhodopsin.
Matuschka S, Zwicker K, Nawroth T, Zimmer G.
Universitatsklinik, Gustav-Embden-Zentrum der Biologischen Chemie, Frankfurt, Germany.
An ATP-synthase complex active in ATP synthesis was isolated from beef heart mitochondria by solubilization of submitochondrial particles with dodecyl-beta-D-maltoside and purified in a one-step procedure by subsequent ion-exchange chromatography. The electrophoretic analysis resulted in 14 subunits for the F0 F1 complex. ATP hydrolysis activity of the purified enzyme was 25 mumol ATP min-1 mg-1F0F1. ATP hydrolysis could be stimulated by addition of lipid vesicles. Further stimulation was observed in the presence of uncoupler. The inhibitors dicyclohexylcarbodiimide and oligomycin reduced hydrolytic activity to 70 and 40%, respectively. The preservation of ATP synthesis capability was demonstrated by reconstitution of the purified enzyme together with the light-driven proton pump bacteriorhodopsin. Upon illumination of ATP-synthase/bacteriorhodopsin proteoliposomes ATP synthesis activity was detectable for at least 7 min. At reduced temperature this time could be increased to 20 min. The maximum synthesis rate of 58 nmol ATP min-1 mg-1 F0F1 was obtained after reconstitution into liposomes made from crude soy bean lecithin by a detergent dialysis procedure using octyl-beta-D-glucopyranoside and monomeric bacteriorhodopsin. ATP synthesis was partially inhibited by oligomycin or dicyclohexylcarbodiimide and was completely abolished in the presence of uncoupler. The ability of the purified enzyme to synthesize ATP shows that the described isolation procedure results in an ATP-synthase complex which is intact in structure and function.
Laxative online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7574667&dopt=Abstract lecithin
Microsc Res Tech. 1997 Oct 1;39(1):85-96.
Imaging supramolecular aggregates in bile models and human bile.
Kaplun A, Konikoff FM, Eitan A, Rubin M, Vilan A, Lichtenberg D, Gilat T, Talmon Y.
Department of Chemical Engineering, Technion, Haifa, Israel.
Investigation of cholesterol crystallization is essential for the understanding of gallstone formation. Previous work has revealed a variety of aggregates of different sizes and shapes prior to the appearance of "classical" plate-like cholesterol monohydrate crystals both in native biles and model systems. In this article, we review existing data based on various microscopic techniques and present data on microstructural pathways leading to cholesterol crystal formation in two different bile models and in native bile. In continuation of our recent investigation of microstructures in nucleating human bile, we now present data suggesting that polymorphism is not limited to complex native bile, but also appears in two, simplified model systems. These studies employed cryo-transmission electron microscopy (cryo-TEM) and video-enhanced light microscopy, using Nomarski optics (VELM). Only the combined use of these two complementary, non-perturbing direct methods can cover the whole range of microstructures ranging from a few nanometers to several microns. Concentrated isotropic solutions of bile models, composed of cholesterol, lecithin and taurocholate, were diluted to induce cholesterol supersaturation and start an evolution of microstructures, leading to cholesterol crystallization. Initially, small spheroidal micelles were observed by cryo-TEM. Subsequently, uni-, oligo- and multilamellar vesicles, compatible with structures seen at the same time by VELM, appeared in coexistence with micelles. Thereafter, during a dynamic phase of cholesterol crystallization, filaments, tubular and helical microstructures, as well as classical plate-like cholesterol monohydrate crystals were noted by light microscopy. Eventually, large plate-like crystal
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