Flocculation and Conductivity of Phosphatide Sols

Physico-chemical experiments with phosphatidyl ethanolamine sols

The solubilities of phosphatidylethanolamine (PE) in some organic solvents have been determined. The results of surface tension studies of aqueous sols of PE show that it has marked surface-active properties and surface ageing occurs. The effect of pH, concentration, mono- and divalent salts on surface activity has been investigated, and discussed in the light of previous theories. The critical micelle concentration is in the range 0·002 to 0·01 per cent w/v. The isoelectric point is at pH 3·1. The effect of mono- and divalent salts on the stability of PE sols has been studied.

Uptake of cerebroside, cholesterol and lecithin by brain myelin and mitochondria

The uptake of emulsified labeled lipids by rat brain myelin and mitochondria was studied. Cerebroside and lecithin uptakes were greatly stimulated by addition of salts, particularly those containing divalent cations. Cholesterol uptake was not influenced by salts. Increasing concentrations of detergent (non-ionic) were inhibitory. Delipidated membranes took up much less lipid, but pretreatment with lecithin partially restored the ability to take up cerebroside and cholesterol. The lipid uptake appears to be nonenzymatic and appears to depend on the size of the emulsified particles. The possible role of such a phenomenon in membrane formation and maintenance is discussed.