References: Lecithin
Biochemistry. 2003 Dec 23;42(50):14921-9.
Molecular logic of 11-cis-retinoid biosynthesis in a cone-dominated species.
Gollapalli DR, Rando RR.
Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 45 Shattuck Street, Boston, Massachusetts 02115, USA.
The biochemical pathway to visual chromophore biosynthesis in rod-dominated animals involves minimally a two component system in which all-trans-retinyl esters, generated by the action of lecithin retinol acyltransferase (LRAT) on vitamin A, are processed into 11-cis-retinol by isomerohydrolase. Possible differences in retinoid metabolism in cone-dominated animals have been noted in the literature, so it was of interest to explore whether these differences are tangential or fundamental. Central to this issue is whether cone-dominated animals use an isomerohydrolase (IMH)-based mechanism in the predominant pathway to 11-cis-retinoids. Here, it is shown that all-trans-retinyl esters (tREs) are the direct precursors of 11-cis-retinol formation in chicken retinyl pigment epithelium/retina preparations. This conclusion is based on at least three avenues of evidence. First, reagents that block tRE synthesis from vitamin A also block 11-cis-retinol synthesis. Second, pulse-chase experiments also establish that tREs are the precursors to 11-cis-retinol. Finally, 11-cis-retinyl-bromoacetate, a known affinity-labeling agent of isomerohydrolase, also blocks chromophore biosynthesis in the cone system.
Laxative online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=14674768&dopt=Abstract lecithin [PubMed - in process]
Biomater Artif Cells Artif Organs. 1989;17(5):563-81.
Oxidative interactions between hemoglobin and egg lecithin liposomes.
Pietrzak WS, Miller IF.
Department of Bioengineering, University of Illinois, Chicago 60680.
The oxidative interaction between hemoglobin and unsaturated egg lecithin liposomes, characterized by the consumption of oxygen and the production of methemoglobin over time, was measured and modelled. The oxygen and methemoglobin profiles were fit by a mathematical model, using numerical integration techniques. From the model, it was determined that the catalytic rate constants for the effect of hemoglobin on lipid peroxidation varied with hemoglobin type, as deoxyhemoglobin greater than oxyhemoglobin = methemoglobin. Under in vivo conditions of oxygen tension, reaction rates were oxyhemoglobin greater than deoxyhemoglobin greater than methemoglobin. Vitamin E had about 35 times the antioxidant activity of cholesterol, as determined by the model. Both additives, together, appeared to stabilize the liposomal membrane, as manifested by their ability to prevent oxidation of approximately 95% of the available lipid.
Laxative online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=2627576&dopt=Abstract lecithin
Indian J Exp Biol. 1994 Jan;32(1):55-9.
Divalent cations and radiation induced lipid peroxidation.
Sitasawad SL, Kale RK.
Radiation Biology Laboratory, School of Life Sciences, Jawaharlal Nehru University, New Delhi, India.
Response of Co2+, Cu2+, Fe2+, Ni2+ and Mn2+ against radiation induced lipid peroxidation has been examined. Liposomes prepared from L-alpha-lecithin were irradiated with or without divalent cations, Co2+ and Cu2+ inhibited lipid peroxidation in concentration dependent manner. On the other hand Fe2+, Ni2+ and Mn2+ enhanced the peroxidation. The enhancement of peroxidation due to Ni2+ was biphasic in nature. Higher concentration of Mn2+ decreased the peroxidation. Except Cu2+ no other cation studied could change the non-linear pattern of radiation induced lipid peroxidation. The pro- or antioxidant effect of divalent cations may be due to their reactivity towards oxygen and oxygen free radicals, and at least in part to their hard/soft acid character.
Laxative online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8045605&dopt=Abstract lecithin
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