The properties of the inorganic dye ruthenium red are presented with emphasis upon its use for electron microscopy of cells and tissues. Although commercial ruthenium red often can be used directly, it always contains various impurities and by-products. One of these, termed ruthenium violet, can be isolated and is useful by itself. Absorption spectra of the ruthenium dyes and common impurities are given so that an assay is possible for any sample. Convenient fixative recipes containing ruthenium red or violet are provided together with constraints necessary for a reliable reaction to label extracellular acidic mucosubstances. Perfusion was not successful. The specificity of the ruthenium red reaction was evaluated by spot testing with 57 substances, and by titration with chemically defined pectins. The results indicate that ruthenium red, as a hexavalent cation, precipitates a large variety of polyanions by ionic interaction, and that its classical reaction with pectin is typical rather than specific. New data are presented regarding its reaction with phospholipids. For electron microscopy, a further reaction with OsO4 amplifies the feeble electron density, which is the counterpart of its intense optical labeling, to a practical level resulting in strong contrast. An hypothesis is presented for the mechanism underlying this intensification.

Ruthenium red and violet. I. Chemistry, purification, methods of use for electron microscopy and mechanism of action

Coordination and organometallic chemistry of metal-NO complexes.

The mutual influence of ligands in transition metal coordination compounds with multiple metal-ligand bonds

The complex cis-(Cl,Cl)-[RuCl2(terpy)(NO)]Cl (1) has been synthesized by the reaction of [RuCl3(H2O)2(NO)] with terpyridine (terpy) and characterized by various spectroscopic, analytical techniques and using electronic structure calculation (DFT) methods. The cytotoxic activity and the DNA-binding properties of 1 have also been studied using biochemical techniques. The results establish unequivocally that 1 corresponds to a so-called [RuNO]6 species, which readily releases the nitrosyl ligand upon irradiation with a mercury lamp in acetonitrile solution. DFT calculations provided a satisfactory description of structural, bonding, electronic and related properties of the new compound and throw light on the mechanism of the photo-induced NO release. Screening on A2780 (human ovarian carcinoma) cell lines showed significant cytotoxicity with an IC50 value of 0.49 µM. 31P and 23Na NMR spectroscopy along with electrophoretic mobility studies illustrated that complex 1 primarily binds by coordination to DNA without any π-interaction between the planar terpy ligand and the DNA bases, while weak electrostatic interactions could not be excluded. Studies on the inhibition of the restriction enzymes DraI and SmaI revealed that 1 prefers the guanine and cytosine bases of DNA.

Synthesis, characterization, in vitro antitumor activity, DNA-binding properties and electronic structure (DFT) of the new complex cis-(Cl,Cl)[RuIICl2(NO+)(terpy)]Cl.

F.S. Martin

Papers

Nitrato and nitro complexes of nitrosylruthenium