Lipoproteins physical properties

Cullis PR, Fenske DB, Fiope MJ Physical properties and functional roles of lipids in membranes. In Biochemistry of Lipids, Lipoproteins and Membranes. Vance DE, Vance JE (editors). Elsevier, 1996. 

Main Physical Properties op Human Sebum High-Density Lipoproteins... 

Lipoproteins are globular, micelle-like particles consisting of a hydrophobic core of triacylglycerols and cholesterol esters surrounded by an amphipathic coat of protein, phospholipid and cholesterol. The apolipoproteins (apoproteins) on the surface of the lipoproteins help to solubilize the lipids and target the lipoproteins to the correct tissues. There are five different types of lipoprotein, classified according to their functional and physical properties chylomicrons, very low density lipoproteins (VLDLs), intermediate density lipoproteins (IDLs), low density lipoproteins (LDLs), and high density lipoproteins (HDLs). The major function of lipoproteins is to transport triacylglycerols, cholesterol and phospholipids around the body. 

The chemical-physical properties of lipoproteins are listed in Table 19.1. It is seen that the density of lipoproteins is lowest for chylomicrons, followed by VLDL, IDL, LDL, and HDL. As density increases, the amount of lipid de-... 

The studies that led to the lipid hypothesis measured plasma total cholesterol concentration. Cholesterol is insoluble in aqueous solution and needs to be combined with protein for transport in blood. These plasma lipoproteins are large heterogeneous aggregates that have different physical properties, such as density, chemical composition and metabolic function (Gurr et al., 2002). 

Studies of the physical properties of UC, reviewed in Chapter 6 of this volume, have contributed much to our understanding of the role of this Upid in membranes and lipoprotein surfaces. The shape and polarity of UC promote its association with the phosphoUpids of membranes and Upoproteins, and this association has important effects on membrane fluidity and permeability. The physical properties of long-chain fatty acid esters of cholesterol, on the other hand, differ strikingly from those of UC, and cause these esters to be largely excluded from phospholipid bilayers and monolayers and to aggregate instead in oil droplets. 

Dandliker M. Moskowitz, B. H. Zimm and M. Calvin The Physical Properties of Elinin, A Lipoprotein from Human Erythrocytes. J. Amer. chem. Soc., in press. (1950). 

Nenseter, M.S., Rustan, A.C., Lund-Katz, S., Spy land, E., Mre-landsmo, G., Philips, M.C., and Drevon, C.A. (1992) Effect of Dietary Supplementation with n-3 Polyunsaturated Fatty Acids on Physical Properties and Metabolism of Low Density Lipoproteins in Hamms, Arterioscler. Thromb. 12, 369-379. 

Avigan (1957) reported that the d 1.063-1.21 lipoprotein class is not essentially affected by ether at 0°. On the other hand, Hayashi et al. (1959), working at higher temperatures (25°C), noted that although a negligible amount of lipids was extracted, a considerable change in physical properties occurred. After ether extraction, the initial single... 

Multi-variable or cold-ethanol precipitation techniques yielded plasma protein fractions rich in lipoprotein (Oncley et al. 1949). These isolation procedures were extremely important. They demonstrated that physical properties such as solubility could be studied with lipoproteins as well as other proteins. Electrophoretic mobilities and specific refractive increments of lipoproteins were shown to be measurable properties (Armstrong et al. 1947 a and 1947 b). A detailed analysis of lipoprotein composition was undertaken (Oncley et al. 1950). 

Lipoprotein classes are not arbitrary segments of an 8f, density, or size continuum. Population distributions for at least two physical properties in one lipoprotein class are distinct from and not continuous with population distributions for the same physical properties in a different lipoprotein class. 

Representative data on the physical properties of chylomicron and very low density lipoprotein classes are compared in Table 1. It is apparent that chylomicrons are readily separated from very low density lipoproteins by ultracentrifugal flotation. The data suggest that a class of particulate lipid, secondary particles, which are distinct from primary particles or chylomicrons, exists in plasma... 

Table 1. Physical properties of chylomicrons, secondary particles, and very low density lipoproteins...

PHYSICAL PROPERTIES AND CHEMICAL COMPOSITION OF HUMAN PLASMA LIPOPROTEINS... 

The lipoproteins are frequently classified according to the density at which they are isolated (Havel et al., 1980). Even though there is rapid exchange of components between lipoproteins, the physical properties (Table 1) and chemical compositions of the major lipoprotein families are essentially constant when isolated... 

Table 1. Physical Properties of Human Plasma Lipoprotein Families...

To study the chemical composition and the physical properties of lipoproteins it is necessary to isolate them from plasma and separate them from each other. This will also be useful in many metabolic studies. There are three basic methods for their isolation separation in the ultracentrifuge gel filtration or precipitation. Ultracentrifugation is costly and time... 

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