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Biomedical subjects

M M Rapport

Publications and source records attributed to M M Rapport.

85 records · Page 5Linked to original sources
PubMed1968

Lipid monolayers: interactions with the apoprotein of high density plasma lipoprotein.

Monolayer techniques were used to study the interactions of various lipids (cholesterol, lysophosphatidyl choline, phosphatidal ethanolamine, phosphatidyl choline, sphingomyelin, stearic acid, and lipids extracted from plasma high density lipoproteins and very low density lipoprotein) with the lipid-free protein subunit of rat plasma high density lipoprotein and with rat plasma albumin. The proteins were injected under the lipid monolayer at fixed area, and the increase in surface pressure (decrease in surface tension) was measured as a function of time. With all lipids, both the rate and magnitude of this increase were greater with the apolipoprotein than with albumin. The degree of film penetration of pure lipid films (at an initial film pressure of 15 dynes/cm) by the two proteins followed the same order: cholesterol > phosphatidal ethanolamine > phosphatidyl choline > stearic acid > sphingomyelin > lysophosphatidyl choline. Other variables studied were protein concentration, initial film pressure, and pH. Two distinctive properties of the apolipoprotein were the penetration of lipid films at pressures above the collapse pressure of the protein, and the formation of a film even at low salt concentration. High surface activity and strong interaction of HDL-protein with lipid monolayers may be associated with the flexibility of the protein molecule due to absence of disulfide bridges. The unusual surface activity of HDL-protein may be intimately related to the mechanism of formation of the lipoprotein.

Animals↗
PubMed1967

An improved preparation of bovine brain proteolipid.

An improved preparation of proteolipid from bovine brain white matter is described. The product obtained by repeated acetone precipitation is completely soluble in chloroform-methanol and has a fairly constant composition: 35% protein, 40% galactocerebroside, and about 25% phospholipid.

Acetone↗
PubMed1966

Enzymic hydrolysis of sphingolipids: Hydrolysis of ceramide lactoside by an enzyme from rat brain.

Ceramide lactoside [1-O-(galactosido-4-beta-glucosido)-2-N-acyl-sphingosine] was hydrolysed to ceramide glucoside and galactose by beta-galactosidase of rat brain. The reaction was not reversible, required cholate or taurocholate, had optimum pH5.0 and K(m) 2.2x10(-5)m. It was inhibited by gamma-galactonolactone and galactose as well as by ceramide, sphingosine and fatty acid. Ceramide lactoside could be degraded to ceramide, galactose and glucose by mixtures of rat-brain beta-galactosidase and ox-brain beta-glucosidase.

Journal Article↗
PubMed1966

Lipid monolayers: action of phospholipase A of Crotalus atrox and Naja naja venoms on phosphatidyl choline and phosphatidal choline.

The activity of phospholipase A on phosphatidyl choline and phosphatidal choline spread as monolayers on phosphate buffers containing snake venom (Crotalus atrox or Naja naja) was studied by measuring the fall of surface potential as a function of time, pH, film pressure, temperature, and concentrations of phosphate and venom. At 25 degrees C, pH 7.0, and 0.2 micrograms of venom per ml, optimal activity was observed with both venoms on both substrates at 12 dynes/cm film pressure on 0.04 m phosphate. Under these conditions, the pH optimum for C. atrox was broad (6.6-7.4) and that for N. naja was sharp (8.0) for the action on phosphatidyl choline, whereas both venoms had a sharp optimum at pH 8.0 in their action on phosphatidal choline. The optimal temperature with phosphatidyl choline was 27.5 degrees C for N. naja and 40 degrees C for C. atrox. In line with studies of phospholipase A activity in bulk phase in ether, phosphatidal choline was attacked much more slowly than phosphatidyl choline by C. atrox. Under conditions where both venoms had equal activity on phosphatidyl choline, C. atrox was only half as active as N. naja on phosphatidal choline. The studies suggest that the linkage of the hydrophobic chains in glycerophosphatides may affect their interaction with proteins.

Animals↗