References: Lecithin
J Lipid Res. 1993 May;34(5):759-68.
Molecular species of lecithins in human gallbladder bile.
Hay DW, Cahalane MJ, Timofeyeva N, Carey MC.
Department of Medicine, Harvard Medical School, Brigham and Women's Hospital, Boston, MA.
Using a precise high performance liquid chromatography (HPLC) technique, we identified the molecular species of lecithins in gallbladder biles from patients with cholesterol gallstones (n = 29), pigment gallstones (n = 9), morbid obesity (n = 5), and "controls" (n = 10). The major lecithin species identified in all groups, in descending rank order as represented by the fatty acids in the sn-1 and sn-2 positions, were 16:0-18:2, 16:0-18:1, 16:0-20:4, 18:0-18:2, and 18:1-18:2. Lecithin species were found to be more numerous and in substantially different proportions than reported by previous investigators. No significant differences were found between any biliary lecithin species in the cholesterol and pigment stone groups. However, compared with controls, both cholesterol and pigment stone patients had smaller proportions of 16:0-20:4, the principal arachidonyl lecithin species. Using the HPLC elution sequence for quantifying the hydrophilic-hydrophobic balance, we developed a Hydrophobic Index for lecithin species in each bile based upon the principles proposed by D. M. Heuman for bile salt species. Hydrophobic indices of bile salts and lecithin were positively correlated (r = 0.48, R2 = 0.23, P = 0.0002) suggesting that more hydrophobic bile salts were associated with biliary secretion of more hydrophobic lecithins. The most hydrophobic major lecithin species, 18:0-18:2, was present in greater proportions in biles with cholesterol monohydrate crystals in their sediments and in those with cholesterol saturation indices greater than one. This work provides rigorous separation, identification, and quantitation of the lecithin species in human gallbladder bile from a large cohort of patients but, apart from a more hydrophobic bile salt pattern coupling mo
Biochim Biophys Acta. 1994 Jun 1;1192(1):14-20.
Electron microscopic investigations on free-standing mixed lipid Langmuir-Blodgett-Kuhn monolayers: phase separation and aging process.
Lieser G, Mittler-Neher S, Spinke J, Knoll W.
Max-Planck-Institut fur Polymerforschung, Mainz, Germany.
Lipid monolayers were prepared by the Langmuir-Blodgett-Kuhn technique (LBK) as free-standing films spanning a diameter of up to 1 micron. These films were investigated by electron spectroscopic imaging (ESI) and electron energy loss spectroscopy (EELS). The free-standing monolayer is shown to be in a transient state in which an aging process is proceeding: after storage for two weeks in air at room temperature the films tear off the edges of the perforated supporting film. Ca2+ ions induced lateral phase separation in these films prepared from a 50:50 mixture of lecithin/glycerol could be visualized by means of ESI, i.e., by comparing micrographs below and above the Ca absorption edge in the EEL spectrum. The domain sizes of the demixed phases were determined to vary between 30 and 60 nm. In addition it was shown that the counter ion of the negatively charged glycerol in these films is Ca2+ and not Na+.
Laxative online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8204644&dopt=Abstract lecithin
J Lipid Res. 1995 Nov;36(11):2355-61.
Secretion of biologically active human proapolipoprotein A-I in a baculovirus-insect cell system: protection from degradation by protease inhibitors.
Pyle LE, Barton P, Fujiwara Y, Mitchell A, Fidge N.
Baker Medical Research Institute, Lipoprotein and Atherosclerosis Unit, Prahran, Australia.
Studies of the structure and function of apolipoprotein A-I (apoA-I) often require its purification by delipidation of high density lipoprotein isolated from large quantities of human plasma and separation of apoA-I from other plasma apolipoproteins. To reduce the need for extensive purification procedures, we have developed an insect cell/baculovirus expression system for the production and secretion of human proapoA-I. The recombinant baculovirus containing full-length human apoA-I cDNA, when introduced into Spodoptera frugiperda, directs the synthesis of preproapoA-I, which is subsequently secreted into the growth medium as proapoA-I, indicating correct processing of the signal peptide during secretion. To prevent the extensive degradation of secreted proapoA-I, leupeptin and pepstatin A were added to the serum free cell culture medium. The protein was simply purified by filtration of the medium, which contained up to 80 mg/l proapoA-I, followed by chromatography on phenyl-sepharose CL-4B. The resultant proapoA-I was found to bind lipid and to activate lecithin:cholesterol acyltransferase as effectively as apoA-I from human plasma. The advantage of this expression system is the ease of purification of intact, biologically active apoA-I in high yield.
Laxative online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8656073&dopt=Abstract lecithin
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