15N NMR studies of the binding of C15N- with gold(I) drugs

15N NMR studies of the interaction of 15N cyanide ion with gold(I)-thiomalate (Autm) and gold(I)-thioglucose (Autg) have been carried out at pH* 7.40. The chemical shifts of the two 15N ions containing species Au(C15N)2- and RS-Au-C15N- (where RS- = tm- or tg-) were identified at 265.94 and 260.30 ppm, respectively. From the broadened 15N NMR signals, approximate life times of the RS-Au-CN- species were calculated.

The 13C NMR study of the binding of gold(I) thiomalate with ergothionine in aqueous solution

The interaction of gold(I) thiomalate (Autm) (Myocrysine) with ergothionine (ErSH) has been studied in aqueous solution at pH 7.4. It was found that ErSH forms a ternary complex of the type ErS-Au-tm at a 1:1 mole ratio; unlike other thiols (e.g., cysteine and glutathione) it does not eject thiomalate (Htm) as a free ligand. However, in the presence of glutathione (GtSH), both ligands, ErSH as well as Htm, from the ErS-Au-tm complex were freed. The 13C NMR chemical shifts of C-2 resonance of ergothionine in the presence of Autm shifts greater than imidazolidine-2-thione (Imt) and 1,3-Diazinane-2-thione (Diaz), indicating the stronger complexation of ErS-Au-tm compared to Imt-Au-tm and Diaz-Au-tm.

Gold(I) efflux from auranofin-treated red blood cells. Evidence for a glutathione-gold-albumin metabolite

The efflux of gold from red blood cells (RBCs) exposed to 10-100 microM auranofin [the second generation chrysotherapy agent, triethylphosphine-(2,3,4,6-tetra-O-acetyl-1-beta-D-glucopyranosato -S-)gold(I)] was studied. RBCs in whole blood were allowed to accumulate gold, and then were placed in fresh plasma or buffered saline solution. In plasma, the kinetics of efflux were first order in gold with an apparent rate constant of 0.81 +/- 0.18 hr-1. Serum albumin, in plasma or added to a buffered solution, shifted the equilibrium between intra- and extracellular gold in favor of the latter (compared to saline solution). [14C]Glutathione, generated by in situ labeling, also effluxed and associated with the albumin and gold, providing the first direct evidence that the albumin-gold-glutathione complex (AlbSAuSG) may be a circulating metabolite of auranofin formed after both of the original ligands of auranofin are displaced.

Synthesis of thionato(triethylphosphine) gold(I) complexes:analogues of "auranofin," an antiarthritic drug

New compounds having the formula [L-Au-PEt3]Cl (where L = imidazolidine-2-thione(Imt) and 1,3-Diazinane-2-thione(Diaz)) are synthesized. They are characterized by elemental analysis, infrared, 13C and 31P NMR spectroscopy.

A reaction between captopril (a high blood pressure drug) and gold(I)-thiomalate

A reaction of gold(I) thiomalates [Au(tm)], "Myocrisin" (an antiarthritic drug), with captopril (a high blood pressure drug) was carried out in aqueous solution at pH 7.20 using 13C NMR spectroscopy. Captopril, which exists in the cis (c) and trans (t) isomer forms, binds strongly with gold(I), ejecting thiomalate (Htm) as free ligand into solution.

A 1H nmr study of the interaction of aurothiomalate ("Myocrisin") with human red blood cells in vitro

The results of 1H spin-echo Fourier transform (SEFT) nuclear magnetic resonance (nmr) experiments suggest that some aurothiomalate binds intracellular glutathione (GSH) when added to suspensions of red cells in vitro. When added to red cell lysates, a specific binding of gold to cysteine of GSH is observed together with release of thiomalate. Gold binding to GSH can be reversed by addition of dimercaptopropanol sulfonate. Spectra are compared to those of an aurothiomalate-GSH model system. The relationship of these findings to the mechanism of action of Myocrisin is discussed.

A proton nuclear magnetic resonance study of the interaction of cadmium with human erythrocytes

The binding of Cd2+ by molecules in the intracellular region of human erythrocytes has been studied by 1H-NMR spectroscopy. From changes in spin-echo Fourier transform NMR spectra for both intact and hemolyzed erythrocytes to which CdCl2 was added, direct evidence was obtained for the binding of Cd2+ by intracellular glutathione and hemoglobin. Time-courses were measured by 1H-NMR for the uptake of Cd2+ by intact erythrocytes in saline/glucose solution and in whole blood. In both cases, the uptake, as indicated by changes in the 1H-NMR spectrum for intracellular glutathione, plateaus after about 30 min. The effectiveness of the disodium salt of EDTA and of various thiol-chelating agents for releasing glutathione from its Cd2 + complexes in hemolyzed erythrocytes was also studied. EDTA was found to be more effective than thiols, and dithiols more effective than monothiols.

H nmr study of the effectiveness of various thiols for removal of methylmercury from hemolyzed erythrocytes

The effectiveness of eight thiol ligands for removing methylmercury (CH3Hg(II)) from its glutathione and hemoglobin complexes in hemolyzed erythrocytes has been studied by 1H nuclear magnetic resonance spectroscopy. These complexes are the predominant methylmercury species in human erythrocytes. The effectiveness was determined from the exchange-averaged chemical shift of the resonance for the proton on the alpha-carbon of the cysteinyl residue and from the intensity of the resonance for the methylene protons of the glycine residue of reduced glutathione (GSH), both of which provide a measure of the amount of glutathione in the CH3Hg(II)-complexed form. The thiol ligands were found to release GSH from its CH3Hg(II) complex in the order 2, 3-dimercaptosuccinic acid greater than mercaptosuccinic acid greater than cysteine greater than mercaptoacetic acid greater than D-penicillamine greater than 2,3-dimercaptopropanesulfonic acid greater than N-acetyl-D,L-penicillamine greater than D,L-homocysteine.

A proton nuclear magnetic resonance study of the interaction of mercury with intact human erythrocytes

The binding of mercuric ion (Hg(II)) by small molecules in the intracellular region of intact human erythrocytes has been studied by 1H-NMR spectroscopy. HgCl2 added to intact erythrocytes in saline-glucose suspension is found to cross the membrane and reach an equilibrium distribution among the molecules of the erythrocyte within 4 min. In the intracellular region Hg(II) reacts with GSH and hemoglobin to form the ternary mixed-ligand complex GSH-Hg(II)-hemoglobin. The analogous complex with ergothioneine is formed after all the GSH is complexed. 1H-NMR spectra show that the GSH-Hg(II)-hemoglobin complex also forms in simpler solutions containing HgCl2, GSH and hemoglobin, whereas the complex Hg(GSH)2 predominates in solutions of GSH and HgCl2. The lifetime of the GSH in the GSH-Hg(II)-hemoglobin complex is shown to be less than 30 s, which provides direct evidence for the first time that Hg(II) complexes in biological systems are quite labile, even though their thermodynamic stability is large. The effectiveness of eight sulfhydryl-containing ligands, some of which have been used as antidotes for Hg(II) poisoning, for releasing GSH from its Hg(II) complex in hemolyzed erythrocytes was also studied. Dithiol ligands were found to be more effective than monothiols, with dithioerythritol the most effective of the dithiols.

A proton nuclear magnetic resonance study of the binding of methylmercury in human erythrocytes

The binding of methylmercury, CH3Hg(II), by small molecules in the intracellular region of human erythrocytes has been studied by 1H-NMR spectroscopy. To suppress or completely eliminate interfering resonances from the much more abundant hemoglobin protons, spectra were measured by a technique based on the transfer of saturation throughout the envelope of hemoglobin resonances following a selective presaturation pulse or by the spin-echo Fourier transform method. With these techniques, 1H-NMR spectra were measured for the more abundant intracellular small molecules, including glycine, alanine, creatine, lactic acid, ergothioneine and glutathione, both intact and hemolyzed erythrocytes to which CH3Hg(II) had been added. The results for intact erythrocytes indicate that part of the CH3Hg(II) is complexed by intracellular glutathione. These results also indicate that exchange of CH3Hg(II) among glutathione molecules is fast, with the average lifetime of a CH3Hg(II)-glutathione complex estimated to be less than 0.01 s. From exchange-averaged chemical shifts of the resonance for the proton on the alpha-carbon of the cysteine residue of glutathione, it is shown that, in hemolyzed erythrocytes, the sulfhydryl group of glutathione binds CH3Hg(II) more strongly than the sulfhydryl groups of hemoglobin.

Reactions of gold(III) ions with ribonuclease A and methionine derivatives in aqueous solution

1. Addition of Au(III) (as chloroaurate) to folded ribonuclease A causes the formation of aggregates, as shown by chromatography and extreme broadening of the 270 MHZ 1H NMR spectrum. 2. When RNAase is partially unfolded Au(III) causes oxidation of methionines to the sulphoxide, and leads to almost complete unfolding (at molar equivalent ratios). 3. Reactions between model methionine derivatives and Au(III) show that the oxidation involves the production of Au(I)-methionine species. The stability of these complexes is dependent on the availability of free NH2 groups which catalyse their disproportionation.