Lipoproteins - protein complexes with lipids.
The composition and properties of lipoproteins vary widely with respect to both the quantity and nature of proteins (see)and lipid components (see Lipids). The most pronounced ability to form complexes with lipids have different globulins, which constitute the prevailing part of the protein that is found in the part of lipoproteins. The lipid part of the complex are usually contains triglycerides, phospholipids (lecithin and Catalina), free cholesterol and its esters. The protein content in litres of blood plasma ranged from 2.5 to 46.4%, the content of free cholesterol - from 2 to 7.5%, cholesterol esters - from 6 to 39.4%, phospholipids from 7,1 to 26.1% and triglycerides - from 8.1 up to 81,3%. In the same range varies and composition L. cells of various tissues.
The nature of relationships between proteins and lipids in Leningrad studied very few. In various L. these relations are not equally strong and stable, but those L., in which connection the most rugged, relatively easy to exchange individual lipid components on related or other lipids environment, as established by experiments with lipids, radiolabelled.
Lipoproteins relatively easily soluble in different salt solutions. L. blood plasma and tissue extracts can be divided into different fractions by means of electrophoresis or ultracentrifugation. During electrophoresis on paper the position of the individual fractions L. determined by the color of lipid components relevant dyes, Sudan and others). The main lipoprotein fractions are the alpha - and beta-lipoproteins (containing α - or beta-globulin). When ultracentrifugation in NaCl solution (with a share 1,063) L. divided into two factions, one of which settles (HP density of 1,063 to 1,210), the other, on the contrary, POPs up (L. density of 1,006 to 1,063). The last fraction but the degree of upwelling (flotation) can be divided into more subfractions, which mark in units Swedberg (S) with the addition of the letters f, which indicates that this is not about settling velocity, and velocity of flotation. Normal serum prevails podrace Sf 0-1,2, i.e. the most severe podrace low density lipoprotein. In atherosclerosis in people who are prone to heart attacks, and a number of other diseases (lipoid nephrosis) often there is a sharp increase in pedrocchi Sf 12-20 and other, even more light subfractions.
Lipoproteins form a special layers in the membranes of all cells and their structural elements (mitochondria and others), causing the membranes permeability for a number of compounds. L. are also carriers of triglycerides, cholesterol and its esters from bodies to the authorities.
Many data shows that changes this feature can be important in the pathogenesis of atherosclerosis and other diseases.
Histochemical definition of lipoproteins in the tissues. HP is not detected by the usual histochemical reaction on lipids (see).
For histochemical detection lipoproteins you must free them from communication with protein by additional pressures, leading to the breakdown of complex or to the destruction of the protein component.
Noll (A. Noll) to identify bound lipids recommends pepsin (0.1 g of pepsin in 100 ml of 0.3% HCl). Good results can also be obtained when exposed to the fabric solutions of neutral salts (15% ammonium chloride or 5% magnesium sulfate), 2% solution of hydrochloric acid or 1% solution of sodium hydroxide. S. S. Weill and E. K. Berezina to identify bound lipids used 15% solution of ammonium chloride. Berenbaum (M. G. Berenbaum) indicates that the associated lipids can be detected by long-term (a few hours) washing of paraffin sections in the water. Gg Nepryakhin recommends to identify Liters of alcohol and specially prepared xiaowei solutions Saganovich dyes. Related lipids partly revealed by the method of I. B. Goldman (color solution of Sudan III, containing alpha-naphthol).