Summary
It was confirmed that purified thromboplastin from human brain tissue contains about 18 amino acids after hydrolysis.
The following observations gave rise to a discussion if these amino acids are to be considered as contaminations only, or if they derived from a protein moiety of brain thromboplastin.
The amino acids are present in all fractions of the thromboplastin and in the wash solutions, and their amount is very small.
The amino acids cannot be removed from thromboplastin with the usual techniques, but amino acids and peptides added on purpose can be separated again.
Investigations with DNFB pointed to the presence of a great number of precipitable small peptides of various composition. The possibility of the presence of a microamount of a long-chain peptide, or even a trace of protein could not be excluded.
Four techniques to separate the amino acid-rich fraction of thromboplastin were studied, described, and the results obtained compared. Sephadex G-25 was most successful, and the fractions were analysed.
Most striking was the percentage of aspartic acid in the non-lipid fraction, which is 13-26 times lower than that of proteins and lipoproteins.
The biological investigations of these fractions are subject of the subsequent paper.
