Studies on phospholipids. 1. The determination of amino nitrogen in unhydrolysed phospholipids

The kephalin content of a fat or tissue has, until recently, been estimated from the difference between the amounts oftotal and choline-containing phospholipids. In contrast to this indirect pro- cedure, several methods for the direct determination have recently been described. Those due to Artom (1945), Levine & Chargaff (1951) and Axelrod, Reichenthal & Brodie (1953) require a preliminary hydrolysis of the fat for 3-6 hr. This hydrolysis can be dispensed with if a reagent is used which will react with the amino groups of the intact fat.