Chemical structure and production of G-NH
-derived metabolite after dialysis against porcine serum. The chemical structures of doubly labeled glycine with two 13C- and one 15N-isotopes (A) which was transformed into labeled glycineamide (B). The latter was dialyzed against porcine serum at 37°C, and the 13C2 15N-labeled product (C) here is referred to as Met-X. This compound was purified by HPLC and concentrated before being analyzed with NMR.