Platelet Phosphatides. Their Fatty Acid and Aldehyde Composition and Activity in Different Clotting Systems*

Previous studies from this laboratory revealed that phosphatidyl serine (PS) isolated from plate- let phospholipid extracts by silicic-acid column chromatography could replace blood platelets in tests of thromboplastin generation and prothrombin consumption of platelet-poor "native" plasma (1, 2). When rigorous criteria of identification were employed, it was found that phosphatidyl ethanolamine (PE) fractions contained traces of PS (2); coagulant properties were therefore difficult to evaluate. Rouser, O'Brien, and Heller (3) recently accomplished the complete separa- tion of PE from PS by means of a double column technique using silicic acid and ammoniated silicic acid. Their studies were carried out on lipids of beef brain, but the methods could be applied to human brain and platelet extracts.