Magnesium ions probes

Ion Probe Magnesium Isotopic Measurements of Allende Inclusions... 

Fig. 10.22. Chelating PCT sensors for calcium and magnesium ions (PCT-11 and PCT-12 Grynkiewicz G. et al. (1985) J. Biol. Chem. 260, 3440. PCT-13 and PCT-14 Haugland R. P., Handbook of Fluorescent Probes and Research Chemicals, 6th edn, Molecular Probes, Inc., Eugene, OR).

Hutcheon ID (1982) Ion probe magnesium isotopic measurements of Allende inclusions. Amer Chem Soc... 

Because muscle cells are especially rich in terms of phosphorus-containing metabolites (e.g., ATP, ADP, phos-phocreatine, and orthophosphate), nuclear magnetic resonance " has proved to be a valuable noninvasive probe of metabolic changes attending muscle activity. The spectral sensitivity of P is especially high relative to other nuclei, and one can detect cellular concentrations as low as 0.5 mM as well as utilize chemical shift data to define intracellular pH and free magnesium ion concentrations. See also Nuclear Magnetic Resonance Chemical Shift... 

B. M. Altura and B. T. Altura, Role of magnesium and calcium in alcohol-induced hypertension and strokes as probed by in-vivo television microscopy, digital image microscopy, optical spectroscopy, P-NMR spectroscopy and a unique magnesium ion-selective electrode. Alcohol. Clin. Exp. Res., 1994,18,1057-1068. 

Feig AL (2000) The use of manganese as a probe for elucidating the role of magnesium ions in ribozymes. Met Ions Biol Syst 37 157-182... 

The Use of Manganese as a Probe for Elucidating the Role of Magnesium Ions in Ribozymes... 

Calcium sensors are merely representative of a much wider class of ion sensors, albeit probably the best understood. Fluorescent probes have now been developed for a wide range of metal ions of biological interest, particularly sodium, potassium, magnesium, and zinc. 

By keeping the same fluorophores, but reducing the cavity size of the ion-ophore, we obtain PCT-13 (Mag-Indol) and PCT-14 (Mag-Fura2) (Figure 10.22), which are selective for magnesium. PCT-8, PCT-9 and PCT-11 to PCT-14 are commercially available in the non-fluorescent acetoxymethylester form so that they are cell permeant and they recover their fluorescence upon hydrolysis by enzymes (Molecular Probes, Inc., Eugene, OR). 

The sensor reported by Shirai(69) used a natural carboxylic polyether antibiotic (Aem = 481 nm) for the detection of magnesium and calcium. Detection limits of I0 5 and KT4 M, respectively, were reported but, interference from other metals was difficult to overcome. Ishibashi(69) used a bulkier hexadecyl-acridine orange dye (Xem = 525 nm) plasticized in a PVC membrane for the fluorescent detection of ammonium ions. Signal interference due to superfluous ions and poor detection limits of KT5 M restricted the use of the probe. 

A metal-nucleotide complex that exhibits low rates of ligand exchange as a result of substituting higher oxidation state metal ions with ionic radii nearly equal to the naturally bound metal ion. Such compounds can be prepared with chromium(III), cobalt(III), and rhodi-um(III) in place of magnesium or calcium ion. Because these exchange-inert complexes can be resolved into their various optically active isomers, they have proven to be powerful mechanistic probes, particularly for kinases, NTPases, and nucleotidyl transferases. In the case of Cr(III) coordination complexes with the two phosphates of ATP or ADP, the second phosphate becomes chiral, and the screw sense must be specified to describe the three-dimensional configuration of atoms. 

Tretyakov and Filimonov (219) describe a coordinative interaction between benzonitrile and aprotic sites on magnesium oxide, and Zecchina et al. (256) came to the same conclusion for the adsorption of propionitrile, benzonitrile, and acrylonitrile on a chromia-silica catalyst. Chapman and Hair (257) observed an additional chemical transformation of benzonitrile on alumina-containing surfaces, which they describe as an oxidation. Knozinger and Krietenbrink (255) have shown that acetonitrile is hydrolyzed on alumina by basic OH- ions, even at temperatures below 100°C. This reaction may be described as shown in Scheme 2. The surface acetamide (V) is subsequently transformed into a surface acetate at higher temperatures. Additional reactions on alumina are a dissociative adsorption and polymerizations (255) analogous to those observed for hydrogen cyanide by Low and Ramamurthy (258), and a dissociative adsorption. Thus, acetonitrile must certainly be refused as a probe molecule and specific poison. 

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