Lipoproteins

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Related to low-density lipoproteins: HDL, LDL-C
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Lipoproteins

 

complexes of proteins and lipids. Lipoproteins occur in plants and animals as constituents of all biological membranes and lamellar structures (in the myelin sheath of nerves, in the chloroplasts of plants, in the receptor cells of the retina). They occur in free form in blood plasma, from which they were first isolated in 1929.

Lipoproteins are classified according to chemical structure and lipid-protein ratio. They are subdivided into four main classes according to sedimentation rate during centrifugal separation: (1) high-density lipoproteins (52 percent protein and 48 percent lipids, primarily phospholipids), (2) low-density lipoproteins (21 percent protein and 79 percent lipids, mainly cholesterol), (3) very low-density lipoproteins (9 percent protein and 91 percent lipids, mostly triglycerides), and (4) chylomicrons (1 percent protein and 99 percent triglycerides).

It is thought that lipoprotein structure is micellar (the protein bonded to the lipid-cholesterol complex owing to hydrophobic interaction) or analogous to that of molecular compounds of proteins and lipids (the phospholipid molecules located in flexures of the polypeptide chains of protein subunits). The study of lipoproteins is complicated by the instability of lipid-protein complexes and by difficulties encountered in their isolation in natural form.

REFERENCE

Finean, J. Biologicheskie ul’trastruktury. Moscow, 1970. (Translated from English.)

N. V. PROKAZOVA

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
Frasheri et al., "Small, dense low-density lipoproteins (LDL) are predictors of cardio- and cerebro-vascular events in subjects with the metabolic syndrome," Clinical Endocrinology, vol.
Enhanced susceptibility of low-density lipoproteins to oxidation in coronary bypass patients with progression of atherosclerosis.
Their cholesterol-shuttling, low-density lipoproteins (LDLs)--the so-called bad lipoproteins--were unusually small and dense.
Cholesterol-carrying low-density lipoproteins (LDLs) in the blood can be oxidized by naturally occurring molecular fragments known as free radicals.
Working with simulated cell membranes and low-density lipoproteins from people who had taken different vitamin E supplements, the scientists tested the tocopherols' ability to detoxify peroxynitrite, a nitrogen oxide that appears to be associated with inflammation.
Yet many physicians have been reluctant to advocate consuming fish oil in large quantities because this natural fat has the drawback of increasing the proportion of cholesterol shuttled through the blood in low-density lipoproteins (LDLs), another major risk factor for heart disease.
In the body, oxidation transforms lipid-rich low-density lipoproteins (LDLs) in the blood into the foam cells that create artery-clogging plaque.
In the generation of heart disease, the oxidative transformation of cholesterol-carrying low-density lipoproteins (LDLs) in the blood leads to the buildup of artery-clogging plaque.
In fact, a relatively fatty milk chocolate bar can be swapped for a low-fat daily snack possessing the same calories without raising low-density lipoproteins in the blood-- a major risk factor in heart disease.
For example, other scientists had determined that CD36, a docking site for oxidized low-density lipoproteins, can lead to the unwanted cholesterol plaques that clog arteries.
Since then, several studies have confirmed the ability of trans fats not only to increase concentrations of "bad," low-density lipoproteins (LDLs) -- as most saturated fats do -- but also to decrease concentrations of "good," high-density lipoproteins (HDLs).
High-density lipoproteins (HDL) -- the good guys -- ferried cholesterol away from artery walls to the liver for disposal, while low-density lipoproteins (LDL) deposited lipids, which could clog arteries.

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