The micro-measurement of lysine in the Cartesian diver

ABSTRACT

0.5-1.0ul. of solution containing lysine is mixed in silicone-coated divers (Waterlow & Borrow, 1949) with 2 ul. of a suspension of L-lysine decarbolylase (Sigma Chemical Co.). Evolution of CO2 is complete after 1 hr. By this method it is possible to estimate 0.01 uM lysine with an accuracy of about 5 percent. The method has been applied to the measurement of the turnover rate of free lysine in the rat during constant intravenous infusion with 14C-lysine. Serial blood samples are taken from the tail to give 100 ul. of plasma. After deproteinazation with picric acid the free amino acid extract is evaporated to dryness and taken up in 5 ul. of acetate buffer pH 5. This provides enough material for two duplicate measurements of lysine content and for measurement of radioactivity (AU)