NOTPME: A 31P NMR probe for measurementof divalent cations in biological systems

Ravichandran Ramasamy, Istvan Lazar, Erno Brucher, A. Dean Sherry, Craig R. Malloy

Research output: Contribution to journalArticlepeer-review

14 Scopus citations


1, 4, 7-Triazacyclononame-N, N′,N′-tris(methylenephosphonate monoethylester) (NOTPME) has been synthesized, characterized and analyzed for use as a 31P NMR indicator of intracellular Mg2+ and Zn2+ ions. The 31P 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 Mg2+ than for Ca2+ at physiological pH values. In the presence of Mg2+, NOTPME is readily loaded into red blood cells. A 31P 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 Mg2+ concentration of 0.32 mM. The 31P 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.

Original languageEnglish (US)
Pages (from-to)121-124
Number of pages4
JournalFEBS Letters
Issue number1
StatePublished - Mar 11 1991


  • Magnesium chelator
  • P NMR indicator

ASJC Scopus subject areas

  • Biophysics
  • Structural Biology
  • Biochemistry
  • Molecular Biology
  • Genetics
  • Cell Biology


Dive into the research topics of 'NOTPME: A 31P NMR probe for measurementof divalent cations in biological systems'. Together they form a unique fingerprint.

Cite this