CHARACTERIZATION OF A PHOSPHONIUM ANALOG OF CHOLINE AS A PROBE IN P-31 NMR-STUDIES OF PHOSPHOLIPID-METABOLISM

Tumors and transformed cells have been shown by P-31 NMR to contain el evated concentrations of two phosphomonoesters, phosphorylcholine and phosphorylethanolamine, involved in phospholipid metabolism. In order to understand the biochemical basis for these phenomena new methods ar e needed to allow for analysis of the relevant metabolic pathways in i ntact cells. One such promising tool may be phosphonium-choline, a P-3 1 NMR-visible analog of choline in which the trimethyl-ammonium group of choline has been replaced with a trimethyl-phosphonium moiety. As s hown previously [Sim et al. Biochem. J. 154, 303 (1976)], this compoun d is non-toxic and readily metabolized by cultured cells into phosphol ipids. In this paper we describe in greater detail some of the chemica l and NMR spectroscopic properties of this material. Most significantl y we show here that the chemical shift of phosphonium-choline is sensi tive to the phosphorylation state of the analog and that the phosphoni um nucleus is NMR-visible even after its incorporation into phospholip id. The unique properties of this analog should make it possible to us e high-field P-31 NMR to follow the flux of phosphonium-choline throug h the Kennedy pathway in intact perfused cells cultures.