Lipoproteins behavior

The rotational mobility of human low-density (LDL) and very-low-density (VLDL) lipoproteins was studied as a function of viscosity and temperature in the range of —90 to — 50°C.(86)The rotational behavior for LDL is represented by a single correlation time, consistent with the overall rotation of a spherical rigid particle as the source of the phosphorescence depolarization. For VLDL, internal peptide motions dominate the depolarization profile. 

When soap is dispersed in a nonpolar phase, inverted micelles are formed in which the nonpolar tails of the soap molecules interact with the bulk solvent while the hydrophilic heads interact with each other. This behavior of amphiphilic molecules explains how they can disperse nonpolar particles in water the hydrocarbon tail of the amphiphile interacts with the particle, such as an oil droplet, dirt, or a lipoprotein membrane fragment, covers the particle, and then presents its hydrophilic head groups to the aqueous phase. 

The major lipoproteins of insect hemolymph, the lipophorins, transport diacylglycerols. The apolipo-phorins have molecular masses of -250, 80, and sometimes 18 kDa.34-37a The three-dimensional structure of a small 166-residue lipophorin (apolipophorin-III) is that of a four-helix bundle. It has been suggested that it may partially unfold into an extended form, whose amphipathic helices may bind to a phospholipid surface of the lipid micelle of the lipophorin 35 A similar behavior may be involved in binding of mammalian apolipoproteins. Four-helix lipid-binding proteins have also been isolated from plants.38 See also Box 21-A. Specialized lipoproteins known as lipovitellins... 

Free fatty acids, derived primarily from adipocyte triglycerides, are transported as a physical complex with plasma albumin. Triglycerides and cholesteryl esters are transported in the core of plasma lipoproteins [134], Deliconstantinos observed the physical state of the Na+/K+-ATPase lipid microenvironment as it changed from a liquid-crystalline form to a gel phase [135], The studies concerning the albumin-cholesterol complex, its behavior, and its role in the structure of biomembranes provided important new clues as to the role of this fascinating molecule in normal and pathological states [135]. 

Conversion of VLDLs to VLDL Remnants in the Bloodstream HDLs and the Cycling of Cholesterol Lipids in Lipoproteins Studies on the Behavior of Lipoproteins Appearance of Chylomicrons in the Bloodstream Following a Meal of Fat or Oil... 

Experimental evidence for a core localization of hydrocarbon was obtained from NMR, calorimetry, and SAXRS studies (Katagiri et al., 1985, 1987). Thus, from the similarity in thermotropic behavior of pure hydrocarbons isolated from locust lipophorin, and the same hydrocarbons in the native lipoprotein, it was concluded that hydrocarbons are partially segregated from the other lipophorin components forming a hydrocarbon-rich cluster. The presence of an internal region of low electronic density was observed by SAXRS in lipophorins containing hydrocarbons, suggesting that hydrocarbons form part of an inner lipid core, which is not exposed to the aqueous environment. 

Green tea catechin. Transgenic mice treated with green tea cate-chin (GTC), a radical scavenger, exhibited decreases in behavioral impairment, Afi production, APP-C99/89 expression, y-sccrctasc component and Wnt protein levels, y-secrctasc activity, and MAPK activation. In contrast, the levels of APP-C83 protein and enzyme activities (a-secretase, neprilysin, and Pin 1) were elevated in the GTC-treated mice, together with a decrease in the levels of total cholesterol and low-density lipoprotein cholesterol, whereas the level of high-density lipoprotein cholesterol increased [267]. 

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