Synthesis and X-ray crystal structure of the dirhenium complex Re2(i-C3H7COO)4Cl2 and its interactions with the DNA purine nucleobases.

The dirhenium complex Re2(i-C3H7COO)4Cl2 was synthesized and characterized by X-ray crystallography, (1)H NMR and electronic spectroscopies, and electrospray ionization-mass spectrometry. The reactions of Re2(i-C3H7COO)4Cl2 with the substituted DNA purine nucleobases guanine (9-methylguanine and 9-ethylguanine) and adenine (9-methyladenine and 9-ethyladenine) were investigated by proton nuclear magnetic resonance and electronic spectroscopies as well as electrospray ionization-mass spectrometry. The data corroborate binding of two 9-methylguanine (or 9-ethylguanine) and 9-methyladenine (or 9-ethyladenine) bases per dirhenium unit in a bidentate fashion, in equatorial positions, via sites N7/O6 and N1/N6, respectively, with concomitant substitution of two carboxylate groups to form a single isomer of cis-Re2(i-C3H7COO)2(nucleobase)2Cl2. The binding of the bases to the dirhenium core disrupts important nucleobase interactions and may have important biological implications with respect to the anticancer activity of dirhenium complexes.

Synthesis, X-ray structure, interactions with DNA, remarkable in vivo tumor growth suppression and nephroprotective activity of cis-tetrachloro-dipivalato dirhenium(III).

In this study we report the synthesis, the X-ray crystal structure and the in vivo tumor growth suppression and nephroprotective activity of bis-dimethylsulfoxide-cis-tetrachlorodi-µ-pivalatodirhenium(III), cis-Re2[(CH3)3CCOO]2Cl4·2(CH3)2SO (I). The interactions of I with DNA were also investigated by electrophoretic mobility shift assays, electronic absorption titrations, ΔTm and viscosity measurements, which indicate that compound I interacts relatively strongly with the DNA (Kb 2.2×10(3)M(-1)), most likely by forming covalent interstrand cross-links, and by kinking and unwinding supercoiled DNA; moreover, DNA cleavage by I is enhanced in the presence of redox-active species. The in vivo antitumor activity of I is considerable and is accompanied by significant elimination of red blood cell and kidney damage. Remarkably, compound I in combination with cisplatin (combined Re-Pt antitumor system) led to suppression of tumor growth or complete tumor elimination. The antihemolytic and nephroprotective abilities of I only or as a part of the Re-Pt antitumor system were established and a possible mechanism for the influence of I on these properties, involving erythropoietin production, is proposed.

Composition changes in the cuticular surface lipids of the helophytes Phragmites australis and Juncus effusus as result of pollutant exposure.

AIM OF THE STUDY: Helophytes like rush and reed are increasingly used for phytoremediation of contaminated water. This study characterises the response of rush and reed plants to chemical stressors such as chlorobenzene, benzene and methyl-tert-butyl ether. The extractable wax layer of the cuticle was chosen for detailed investigations due to its multiple, particularly, protective functions for plants and its easy availability for analysis. METHODS: The chemical composition of the cuticle wax layer of reed and rush was studied in dependence on chemical stress caused by contaminated water under wetland cultivation conditions. The lipid layer of leaves was extracted, derivatised and investigated by GC-MS using retention time locking and a plant-specific data base. RESULTS: In case of rush, a remarkable increase of the total lipid layer and a prolongation of the mean chain length resulted as response on a chlorobenzene exposure. The significant difference in the substance profiles of exposed plants and controls could be confirmed by multivariate data analysis. The lipid layer of reed was not changed significantly when the plants were exposed to water polluted with benzene and methyl-tert-butyl ether. However, scanning electron microscopic images of the exposed reed leaves indicated alterations in the crystal structure of their wax surface. CONCLUSION: The composition and morphology of cuticular waxes indicated the plants' response to chemical stress very sensitively thus, changes in the wax layer could be used as an indication for growing in a contaminated area.

Synthesis, characterization, in vivo antitumor properties of the cluster rhenium compound with GABA ligands and its synergism with cisplatin.

A new dirhenium(III) complex cis-[Re2(GABA)2Cl5(H2O)]Cl.2H2O with zwitterionic gamma-aminobutyrate ligands was prepared and characterized by spectral methods and crystallography. The structure of the compound is comprised of dinuclear complex cations (Re-Re 2.2437(3) A) involving cis-oriented double carboxylate bridges, four equatorial chloride ions and two weakly bonded aqua and chloride ligands in the axial positions at two rhenium centers (Re-O 2.363(3), Re-Cl 2.6735(12) A). Antitumor properties of the complex were studied in the model of tumor growth with the use of Wistar rats inoculated by tumor carcinoma Guerink cells. The introduction of the compound in dosage according to the scheme of antioxidant therapy, inhibited the tumor growth by ca. 60% and led to stabilization of red blood cells in the tumor-bearing organisms. The combined introduction of the compound and cisplatin had a significant impact on the tumor growth and the disappearance of the tumors in most of the animals.

Liposomal forms of rhenium cluster compounds: enhancement of biological activity.

Liposomal formulations of dinuclear cluster rhenium (Re) compounds were used in biochemical trials. Interaction of liposomal forms of some Re compounds with red blood cells in experiments in vitro showed strong cell-stabilizing properties. In the models of tumor growth and hemolytic anemia in vivo, liposomal forms had better therapeutic effects in comparison with their solutions. The process of formation of liposomes of cluster Re compounds with different organic ligands was investigated by the method of electronic absorption spectra and mechanism of their interactions with lipids is proposed. Encapsulation of cluster Re compounds to lipid coating may have activation significance for the quadruple Re-Re bond.