Structure of the phosphatidylcholines of the lung surfactant at birth in normal full term infants.

1. This investigation was undertaken for the purpose of determining the structure of the phosphatidylcholines of lung surfactant system present at birth in normal full term newborn infants. 2. The procedure, using tracheal aspirates as lung secretions, combines a cold-acetone precipitation and a two-dimensional thin-layer chromatography of the lipid extract. 3. Different species of phosphatidylcholines were isolated and found to account together for over 60% of the total phospholipids in tracheal aspirates. Analysis of the fatty acids esterifying the alpha- and beta-carbon of these different phosphatidylcholines showed palmitic acid as the major component with little myristic acid. 4. This fatty acid analysis revealed furthermore that the major phosphatidylcholine fraction was almost exclusively alpha, beta-dipalmitoylphosphatidylcholine. 5. This study shows that the procedure described provides a useful and simple method for the extraction, isolation and characterisation of the functional components of lung surfactant in living human newborns.