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NOTPME: A 31 P NMR probe for measurementof divalent cations in biological systems
Author(s) -
Ramasamy Ravichandran,
Lazar Istvan,
Brucher Erno,
Sherry A.Dean,
Malloy Craig R.
Publication year - 1991
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(91)80218-r
Subject(s) - chelation , divalent , chemistry , intracellular , nuclear magnetic resonance spectroscopy , tris , metal , metal ions in aqueous solution , ion , chemical shift , intracellular ph , proton nmr , nuclear chemistry , inorganic chemistry , stereochemistry , biochemistry , organic chemistry
1, 4, 7‐Triazacyclononame‐ N, N′,N′ ‐tris(methylenephosphonate monoethylester) (NOTPME) has been synthesized, characterized and analyzed for use as a 31 P NMR indicator of intracellular Mg 2+ and Zn 2+ ions. The 31 P NMR spectrum of this chelate in the presence of metal ions shows characteristics resonances for the free chelate, Mg(NOTPME) − , Zn(NOTPME) − and Ca(NOTPME) − . The K ??? values indicate that this chelate has a 10‐fold higher affinity for Mg 2+ than for Ca 2+ at physiological pH values. In the presence of Mg 2+ , NOTPME is readily loaded into red blood cells. A 31 P NMR spectrum of red cells taken after several washing shows resonances characteristics of entrapped NOTPME and the Mg(NOTPME) − complex, the relative areas of which report an intracellular free Mg 2+ concentration of 0.32 mM. The 31 P chemical shifts of the free chelate and its metal complexes are far downfield from the typical phosphorus‐containing metabolites observed in biological systems, thus making it possible to monitor intracellular cation concentration and cell energetics simultaneously.