Natural Abundance of N 15 in Hemin and Plasma Protein from Normal Blood. ∗

Abstract

Summary

Hemin and plasma protein isolated from normal blood were found to have a slightly increased abundance of N¹⁵ over tank nitrogen or ammonium chloride. The mean values for normal hemin, 0.0046, and for normal plasma protein, 0.0039 atom % excess N¹⁵, were similar to the N¹⁵ concentration found in urinary urea. These results lend further support to the idea that minute fractionation of the nitrogen isotopes might occur through normal biological processes.