Lipid protein particles

RELEASE OF LIPID CATABOLITES FROM MEMBRANES BY BLEBBING OF LIPID-PROTEIN PARTICLES... 

Osmiophilic lipid-protein particles enriched in membrane lipid catabolites have been isolated from the cytosol of carnation petals and of cotyledons (Phaseolus vulgaris) by ultrafiltration or flotation centrifugation [2,3]. The particles are spherical in nature and range from 150 to 300 nm in diameter [Fig. 1]. Osmiophilic particles of similar size and shape are also detectable in the cell cytoplasm [3]. The particles contain phospholipid, but are enriched (10- to 100- fold) by comparison with membranes in free fatty acids, triacylglycerols, and steiyl and wax esters [Fig. 2]. 

Several observations support the contention that cytosolic lipid-protein particles originate from membranes. In particular, they contain phospholipid with the same fatty acids, albeit in different proportions, found in phospholipid of corresponding microsomal membranes [3]. In addition, lipid-protein particles with essentially similar properties can be generated in vitro from isolated microsomal membranes under conditions in which phospholipid catabolism has been activated by the addition of Ca [2,3]. The finding that the particles contain high concentrations of free fatly acids and steryl and wax esters suggests that they are formed at specific... 

Figure L Electron micrograph of cytosolic lipid-protein particles isolated from carnation petals and stained with uranyl acetate. Bar = 100 nm.

Figure 2. Thin layer chromatogram of total lipids extracted from microsomal membranes (lane 1) and cytosolic lipid-protein particles (lane 2) isolated from cotyledon tissue of Phaseolus vulgaris. PC, phosphatidylcholine PE, phosphatidylethanolamine PG, phosphatidylglycerol PI, phsophatylinositol FFA, free fatty acids TAG, triacylglycerol SE/WE, steryl and wax esters.

Figure 3. Wide angle X-ray diffraction pattern recorded at 25°C from a hydrated mixture of free fatty acids and steryl and wax esters isolated from cytosolic lipid-protein particles of Phaseolus vulgaris cotyledon tissue. Arrows denote X-ray reflections derived from gel phase packing.

Hudak, K.A., and Thompson, J.E. Flotation of lipid-protein particles containing triacylglycerol and phospholipid from the cytosol of carnation petals. Physiol Plant, (in press). 

Release of Lipid Catabolites from Membranes by Blebbing of Lipid-Protein Particles. J.E. Thompson, C.D. Froese, Y. Hong, K.A. Hudak and M.D. Smith. 

Transports into ER proteins destined for plasma membrane, secretion, or organelles Shuttles proteins between nucleus and cytoplasm Imports, by receptor-mediated endocytosis, lipid carrying particles... 

Figure 4. Fluorescence micrograph of a ciyosection of chocolate stained for protein with ANS. The protein particles in chocolate are discrete and there is little cross-reactivity of the dye with the lipids. Epifluorescence optics (x 230).

Kohane, D.S. Lipp, M. Kinney, R.C. Lotan, N. Langer, R. Sciatic nerve blockade with lipid-protein-sugar particles containing bupivacaine. Pharm. Res. 2000, 17 (10), 1243-1249. 

Santos, I.R.D. Richard, J. Pech, B. Thies, C. Benoit, J.P. Microencapsulation of protein particles within lipids using a novel supercritical fluid process. Int. J. Pharm. 2002, 242 (1-2), 69-78. 

From this emulsion particle model, it was possible to predict the lipoprotein composition, buoyant density, and hydrodynamic properties of the LDL as a function of lipoprotein size, given the partial specific volumes of the lipid, protein, and carbohydrate components. A cross-sectional slice through the model is shown in Fig. 3 as two concentric circles, representing the hydrophobic core surrounded by a monolayer of phospholipid, cholesterol, and protein. The model parameters are given in the footnote to Table II and include the thickness of the shell, the... 

Calculated from the emulsion particle model, given the size of the apoB, the observed density, and the partial specific volumes of the constituent lipid, protein and carbohydrate, a 1 1 molar ratio of C to PL, a 25 6 wt ratio of TG CE (Thrift et al., 1986), and a shell thickness of 20.2 A. 

Figure 27-1 Predicted Influence of water content on sodium measurements for a lOOmmol/L NaCi solution by direct ion-selective electrode (tSE versus flame emission photometry or indirect ISE). Hatched areas represent nonaqueous volumes, which could consist of lipids, proteins, or even a slurry of latex or sand particles. (From Apple FS, Koch DD, Graves S, Ladenson JH. Relationship between d/rect-potent/ometric and flame-photometric measurement of sodium in blood. Clin Chem 1982 28 1931-5.)...

Lipid domains and rafts in biological membranes are stabilized by several different interactions, including membrane-cytoskeleton, lipid-protein, and lipid-lipid interactions, and the organization can be both equilibrium and non-equilibrium in nature [27]. Lipid-domain formation caused by cooperative phenomena in the lipid bilayers is particularly important for the activation of SPLA2 [32-35]. The cooperative phenomena in lipid bilayers are caused by the fundamental interactions between the lipid molecules and are a consequence of the many-particle character of the supramolecular aggregate. The cooperativity leads to phase transitions and phase equilibria. The key cooperative event in many liposomal membranes is the so-called main phase transition, which takes the bilayer from a solid (gel) phase with conformationally ordered acyl chains to a fluid phase with conformationally disordered chains. The main transition in lipid bilayers is often accompanied by strong lateral density and compositional fluctuations. These fluctuations are manifested as dynamic lipid domains characterized by certain time and length scales that are determined by the thermodynamic conditions and the actual lipid species in question. 

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