Lipids browning

The resultant mixture is extracted with CHCI3 (3x200 ml). The chloroform extract is separated, dried with magnesium sulfate and solvent evaporation under vacuum to yield a brown lipid residue. 

D.A. Brown, Lipid droplets Proteins floating on a pool of fat, Curr. Biol., 2001, 11, 446-449. 

Solutions in contact with polyvinyl chloride can become contaminated with trace amounts of lead, titanium, tin, zinc, iron, magnesium or cadmium from additives used in the manufacture and moulding of PVC. V-Phenyl-2-naphthylamine is a contaminant of solvents and biological materials that have been in contact with black rubber or neoprene (in which it is used as an antioxidant). Although it was only an artefact of the separation procedure it has been isolated as an apparent component of vitamin K preparations, extracts of plant lipids, algae, livers, butter, eye tissue and kidney tissue [Brown Chem Br 3 524 1967]. 

Gel permeation ehromatography (GPC)/normal-phase HPLC was used by Brown-Thomas et al. (35) to determine fat-soluble vitamins in standard referenee material (SRM) samples of a fortified eoeonut oil (SRM 1563) and a eod liver oil (SRM 1588). The on-line GPC/normal-phase proeedure eliminated the long and laborious extraetion proeedure of isolating vitamins from the oil matrix. In faet, the GPC step permits the elimination of the lipid materials prior to the HPLC analysis. The HPLC eolumns used for the vitamin determinations were a 10 p.m polystyrene/divinylbenzene gel eolumn and a semipreparative aminoeyano eolumn, with hexane, methylene ehloride and methyl tert-butyl ether being employed as solvent. 

BROWN M s and goldstein j l (1990) Scavenging for receptors Nature 343, 508-9. ESTERBAUER H, GEBiKi J, PUHL H and JURGENS G (1992) The role of lipid peroxidation and antioxidants in oxidative modification of LDL Free Radical Biology and Medicine 13, 341-90. 

Microbial growth, enzymatic reactions, non-enzymatic browning (reaction between carbonyl and amino compounds), and lipid oxidation are the major deterioration mechanisms that limit the stability of low moisture (o intermediate moisture foods (o.6o < <0.85) and biological materials. 

To fulfill the needs for long term stability of a biological material, the optimum range of water activity lies between 0.20 and 0.35, This area represents the best compromise between lipid oxidation and non-enzymatic browning. Enzymatic browning is suppressed under these conditions, and growth of microorganisms is impossible. 

Acetylcholine is formed from acetyl CoA (produced as a byproduct of the citric acid and glycolytic pathways) and choline (component of membrane lipids) by the enzyme choline acetyltransferase (ChAT). Following release it is degraded in the extracellular space by the enzyme acetylcholinesterase (AChE) to acetate and choline. The formation of acetylcholine is limited by the intracellular concentration of choline, which is determined by the (re)uptake of choline into the nerve ending (Taylor Brown, 1994). 

Beta-1, beta-2, and beta-3 adrenergic receptors are G-protein-coupled receptors. Beta-1 and beta-2 receptors mediate the positive inotropic, chronotropic, and dro-motropic effects of the endogenous catecholamines epinephrine and norepinephrine. The beta-3 subtype seems to play a role in regulating thermogenesis and lipid mobilization in brown and white adipose tissue. Several coding and promoter polymorphisms of these receptors have been identified. Clinical studies in asthma... 

Silvius, J.R., Leventis, R., Brown, P.M., and Zuchermann, M. (1987) Novel fluorescent phospholipids for assays of lipid mixing between membranes. Biochemistry 26, 4279-4287. 

The major types of adipose tissue are (1) white adipose tissue, which manufactures, stores, and releases lipid and (2) brown adipose tissue, which dissipates energy via uncoupled mitochondrial respiration. Obesity research includes evaluation of the activity of adrenergic receptors and their effect on adipose tissue with respect to energy storage and expenditure or thermogenesis. 

London, E. and Brown, D. A. (2000) Insolubility of lipids in triton X-100 physical origin, and relationship to sphingolipid/cholesterol membrane domains (rafts) Biochim. Biophys. Acta 1508,182-195. 

Iodine vapour Place the dried plate in a sealed tank containing a few iodine crystals Dark yellow-brown spots appear within a few minutes where lipids have absorbed the iodine. Unsaturated lipids are more intensely stained. Glycolipids do not stain significantly... 

P. M. Elias, E. R. Cooper, A. Korc, and B. E. Brown. Percutaneous transport in relation to stratum corneum structure and lipid composition. J. Invest. Dermatol. 76 297-301 (1981). 

J. R. Brown, R Shockley, Serum Albumin Structure and Characterization of Its Ligand Binding Sites , in Lipid-Protein Interactions , Eds. P. C. Jost, O. H. Griffith, Wiley, New York, 1982, Vol. 1, p. 25-68. 

Brown, A.J., Dean, R.T., and Jessup, W., 1996, Free and esteiified oxysterol formation during copper-oxidation of low density hpoprotein and uptake by macrophages, /. Lipid Res. 37 320-335. 

---