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PubMed2000

Evidence of gold-gold intra- and intermolecular interactions gained by laser desorption/ionisation and fast atom bombardment mass spectrometry in the study of some gold(I) coordination compounds

The mass spectrometric behaviour of some two-coordinated linear gold(I) complexes has been studied by fast atom bombardment (FAB) and laser desorption/ionisation (LDI) methods. The results obtained demonstrate some interesting aspects of Au-Au interactions. The detection under FAB conditions of Au(n)(+) clusters, in particular of Au(3)(+) species, can be rationalised by the presence of significant intramolecular Au-Au interactions, while the formation under LDI conditions of Au(n)(+) clusters can be considered indicative of Au(ellipsis)Au intermolecular interactions present in the solid state. Copyright 2000 John Wiley & Sons, Ltd.

Journal Article↗
PubMed1996

Solid State Structures and Gold-Gold Bonding in Luminescent Halo(dimethylphenylphosphine)gold(I) Complexes.

The structures of the series of two-coordinate gold(I) complexes {(Me(2)PhP)AuX}(n) where X is Cl, Br, or I have been examined by X-ray diffraction. The chloro complex crystallized in two separate polymorphic forms. Colorless hexagonal blocks of {(Me(2)PhP)AuCl}(3) crystallized in the monoclinic space group P2(1)/m with a = 12.141(4) Å, b = 8.433(2) Å, c = 14.834(3) Å, and beta = 94.15(2) degrees at 130 K with Z = 2. Refinement of 2837 reflections and 177 parameters yielded R = 0.066 and R(w) = 0.069. The complex consists of three nearly linear P-Au-Cl units that are connected by Au-Au contacts at 3.091(2) and 3.120(2) Å. Colorless prisms of {(Me(2)PhP)AuCl}(2) form in the orthorhombic space group P2(1)2(1)2(1) as described earlier (Cookson, P. D.; Tiekink, E. R. T. Acta Crystallogr. 1993, C49, 1602). The two nearly linear P-Au-Cl units are staggered and connected through a Au-Au bond (3.230(2) Å). Colorless rectangular prisms of {(Me(2)PhP)AuBr}(2) form in the monoclinic space group P2(1) with a = 9.572(5) Å, b = 8.757(3), and c = 12.915(7) at 130 K with Z = 2. Refinement of 2469 reflections with 118 parameters yielded R = 0.080 and R(w) = 0.084. {(Me(2)PhP)AuI}(2) is isomorphous with the bromo complex with a = 9.736(2) Å, b = 8.890(2) Å, and c = 13.160(5) Å at 130 K with Z = 2. Refinement of 2796 reflections with 119 parameters yielded R = 0.052 and R(w) = 0.058. These complexes are similar to the chloro dimer but with altered orientations of the phenyl substituent. The predicted order of ligand effects (Cl > Br > I) on Au-Au distances from quasi-relativistic calculations is borne out in the experimental values: 3.230 Å (Cl); 3.119 Å (Br); 3.104 Å (I). In dichloromethane, these complexes dissociate into monomeric units but there is some evidence for the presence of dimers in concentrated solutions of the iodide compound.

Journal Article↗
PubMed2002

Catalytic role of gold in gold-based catalysts: a density functional theory study on the CO oxidation on gold.

Gold-based catalysts have been of intense interests in recent years, being regarded as a new generation of catalysts due to their unusually high catalytic performance. For example, CO oxidation on Au/TiO(2) has been found to occur at a temperature as low as 200 K. Despite extensive studies in the field, the microscopic mechanism of CO oxidation on Au-based catalysts remains controversial. Aiming to provide insight into the catalytic roles of Au, we have performed extensive density functional theory calculations for the elementary steps in CO oxidation on Au surfaces. O atom adsorption, CO adsorption, O(2) dissociation, and CO oxidation on a series of Au surfaces, including flat surfaces, defects and small clusters, have been investigated in detail. Many transition states involved are located, and the lowest energy pathways are determined. We find the following: (i) the most stable site for O atom on Au is the bridge site of step edge, not a kink site; (ii) O(2) dissociation on Au (O(2)-->2O(ad)) is hindered by high barriers with the lowest barrier being 0.93 eV on a step edge; (iii) CO can react with atomic O with a substantially lower barrier, 0.25 eV, on Au steps where CO can adsorb; (iv) CO can react with molecular O(2) on Au steps with a low barrier of 0.46 eV, which features an unsymmetrical four-center intermediate state (O-O-CO); and (v) O(2) can adsorb on the interface of Au/TiO(2) with a reasonable chemisorption energy. On the basis of our calculations, we suggest that (i) O(2) dissociation on Au surfaces including particles cannot occur at low temperatures; (ii) CO oxidation on Au/inactive-materials occurs on Au steps via a two-step mechanism: CO+O(2)-->CO(2)+O, and CO+O-->CO(2); and (iii) CO oxidation on Au/active-materials also follows the two-step mechanism with reactions occurring at the interface.

Journal Article↗
PubMed1992

Activation of gold-reactive T lymphocytes in rheumatoid arthritis patients treated with gold.

OBJECTIVE: To assess the role of T lymphocyte sensitization in the etiology of side effects of gold therapy in patients with rheumatoid arthritis (RA). METHODS: Lymphocyte proliferation induced by gold(III) and gold(I) salts was measured in 53 subjects: 30 RA patients with gold-induced side effects (17 with dermatitis, 9 with proteinuria, 3 with hematologic complications, and 1 with colitis), 9 RA patients without side effects despite prolonged chrysotherapy, 4 RA patients who had never received gold, and 10 healthy controls. Peripheral blood lymphocytes were cultured with the different gold salts and proliferation was measured by 3H-thymidine incorporation. RESULTS: Thirteen of the 17 RA patients who developed gold-induced dermatitis showed significant T lymphocyte proliferation in response to gold(III) salts, and this proliferation could be completely blocked by monoclonal antibodies directed at the HLA-DR molecule. Such proliferative responses were not seen in patients with other gold-induced side effects, in patients who had never received gold, or in healthy controls. Only 1 of 9 patients who had not developed side effects despite long-term maintenance chrysotherapy showed significant lymphocyte activation with gold(III) salts. Lymphocyte proliferation could not be induced with gold(I) salts or with other metal salts. CONCLUSION: Patients with RA who develop dermatitis following treatment with sodium aurothiomalate [gold(I)] have T cells which proliferate in an HLA-DR-restricted manner in response to HAuCl4 [gold(III)]. We believe this observation can lead to more accurate diagnosis and treatment of side effects, which currently limit the use of one of the most effective antirheumatic drugs.

Adult↗
PubMed1986

Inter-strand cross-links and single-strand breaks produced by gold(I) and gold(III) coordination complexes.

The ability of gold coordination complexes to bind to DNA and produce inter-strand cross-links in DNA was assessed in an assay system based on the fluorescence properties of the DNA intercalative dye, ethidium bromide. Results from these studies using a variety of gold(I) and gold(III) complexes suggest that the ability of gold complexes to bind to and produce inter-strand cross-links in DNA is not dependent on the oxidation state of gold in the complex but is influenced by the nature of the coordinating ligands. Those complexes in which the gold was ligated through one or more weakly coordinating ligands showed evidence for DNA binding. However, only those complexes with two or more of these relatively weak coordinating ligands produced inter-strand cross-links. Both the amount of binding to and cross-linking of DNA by these compounds were decreased by treatment of the gold-DNA complex with 2-mercaptoethanol and other thiol containing agents. As shown by agarose gel electrophoresis, 2-mercaptoethanol caused a dissociation of the gold-DNA complexes and a regeneration of closed circular superhelical pBR322 DNA. DNA strand breakage also resulted from treatment of a number of gold-DNA complexes with 2-mercaptoethanol; this was observed with the gold compounds which were shown to produce inter-strand cross-links in DNA. The amount of DNA strand breakage produced by treatment of gold-DNA complexes with 2-mercaptoethanol was influenced by the initial conformation of the DNA; gold-DNA complexes which resulted from the binding of gold compounds to covalently closed superhelical DNA were more sensitive to the breakage induced by 2-mercaptoethanol treatment than those complexes in which closed circular, relaxed DNA was used as substrate. The DNA breakage was not reduced in partially anaerobic conditions or by free-radical scavengers, suggesting that it is not mediated by oxygen. The results are discussed with respect to the potential for the interaction of gold complexes with intracellular DNA and chromatin and their biological implications.

Anaerobiosis↗
PubMed1992

Effective diameters of protein A-gold and goat anti-rabbit-gold conjugates visualized by field emission scanning electron microscopy.

High-voltage (15-30 kV) field emission scanning electron microscopy (FESEM) was used to evaluate the effects of gold particle size and protein concentration on the formation of protein-gold complexes. Six colloidal gold sols were prepared, ranging in diameter from 7.6 to 39.8 nm. The minimal protecting amounts (m.p.a.) of protein A and goat anti-rabbit antibody (GAR) were experimentally determined. Gold particles were conjugated at the m.p.a., one half the m.p.a., and ten times the m.p.a. for both proteins, and protein-gold complexes prepared for FESEM. The smallest colloidal gold particles required the most protein per milliliter of gold suspension for stabilization. Transmission electron microscopy was found to be the preferred method for accurate sizing of gold particles, whereas FESEM of protein-gold complexes permitted visualization of a protein halo around a spherical gold core. Protein halo width varied significantly with changes in gold particle size. Measurements of protein halos indicated that conjugation with the m.p.a. of protein A resulted in the thickest protein layers for all gold sizes. GAR conjugation with the m.p.a. again produced the thickest protein layers. However, GAR halos were significantly smaller than those obtained with protein A conjugation. The proteins used showed similar adsorption patterns for the larger gold particles. For smaller gold particles, proteins may act differently, and these complexes should be further characterized by low-voltage FESEM.

Animals↗
PubMed2001

Enhanced photo--catalytic activity of gold ion and gold modified.

The gold ion modified TiO2 was prepared by means of sol-gel whereas gold deposited TiO2 was prepared by means of photo-reduction. The physical properties were influenced significantly by the presence of gold ion or gold. The enhanced photo-activity of gold modified TiO2 was quantified in terms of methylene blue degradation. The presence of gold ion in TiO2 lattices or gold on TiO2 surface enhanced their photo-activity. The optimum molar content of gold ion doping and gold deposition all was 0.5%. The first-order rates constants of gold modified TiO2 was more than that of pure TiO2, and decreased by increasing the content of gold ion and gold when their contents were more than 0.5%. Gold ion doped in TiO2 lattices was more effective to enhance the photo-activity than gold on TiO2 surface. Moreover, the relationship between physical properties, chemical properties and photo-activity has been discussed.

Binding Sites↗
PubMed1996

Relative gold-binding capacity of metallothionein: studies in renal cytosols of gold-injected rats.

To determine the gold-binding capacity of metallothionein (MT) in cytosols of gold-injected rats, we examined the relationship between gold contents in cytosols and in MT fraction in rat kidneys. Each rat was injected intraperitoneally once with 0.9% NaCl or gold (5, 10 or 20 mg gold/kg b.w.). The gold contents in kidneys and in MT fraction increased following the injected amount of gold. The distribution profiles of the renal cytosols of gold-injected rats on a Sephadex G-75 column showed that the amount of the increased gold was attributable to the high molecular weight proteins (HP) and the MT fractions. There were close relationships between the gold contents in cytosol and in MT fractions, and between the gold contents in cytosol and in HP fractions. These results demonstrate that 14% of the increased gold in the renal cytosols of gold-injected rats was bound to MT and that 79% of the increased gold was bound to HP. Our results suggest that the role of metallothionein in gold accumulation in kidneys is different from that in zinc accumulation in kidneys.

Animals↗
PubMedDate not supplied

[Protein binding of gold in serum of patients treated with different gold preparations].

Binding of gold to serum proteins of patients treated with Na-aurothiomalate (AM), gold keratinate (GK) and triethylphosphine gold (PG) was compared. In addition the pattern of distribution of gold in serum of healthy donors after in vitro incubation with these compounds and with tetrachlorogoldacid (GC) was studied. Serum specimens were fractionated by gel filtration (Sephadex G 200), gold was measured by atomic absorption spectroscopy, concentration of protein was calculated by extinction at 280 nm. After incubation with AM, PG and GC in vitro gold binds to serumproteins rapidly and completely (concentration of gold with AM and GC about 5 mg/l, with PG about 1 mg/1). The distribution among the protein fractions is different, however. With AM and GC 94% of gold is bound to albumin and only 6% to globulin. The corresponding figures with PG are 70% respectively 30%. With GK gold binds not completely to serum proteins in vitro. Even after 24 hours incubation about 7% are unbound. The affinity to globulin is high with GK (20%). On principle the pattern of distribution of gold is the same in vivo. The concentration of gold in the serum was almost the same as during the in vitro experiments. No unbound gold was found with GK. The affinity to globulin increases from AM to GK and especially to PG. The reason for these typical patterns are at least in part different metabolic pathways of the gold compounds. These findings may explain some differences of efficacy of certain goldcompounds.

Anti-Inflammatory Agents↗
PubMed1992

[A case of gold lung with positive lymphocyte stimulation test to gold, using bronchoalveolar lymphocytes].

Gold lung, a gold-induced pneumonitis, is considered to be caused by hypersensitivity reaction to gold. We performed lymphocyte stimulation test (LST) to determine the response to gold, using lymphocytes obtained by bronchoalveolar lavage (BAL) from a patient with gold lung. A 57-year-old man was admitted with progressive shortness of breath following a skin eruption. He had been receiving weekly sodium gold thiomalate (Shiosol) for rheumatoid arthritis, with a cumulative dose of 485 mg. Chest roentgenogram showed diffuse interstitial infiltrates. LST for the response to gold, using peripheral lymphocytes, was positive. T cell lymphocytosis was observed in BAL, and transbronchial lung biopsy showed lymphocytic alveolitis and granulation tissue in alveolar ducts. From these findings, we diagnosed gold lung. Prednisolone (PSL) was started with an initial dose of 30 mg/day and resulted in a rapid improvement. As the dose of PSL was tapered, the patient's condition deteriorated and he was treated with a maintenance dose of 10 mg PSL. The second BAL revealed persistent lymphocytosis, and LST using bronchoalveolar lymphocytes for response to gold was positive. LST using peripheral lymphocytes was also positive, but was weaker than that using bronchoalveolar lymphocytes. This is the first report in Japan of a positive LST for response to gold, using bronchoalveolar lymphocytes from a patient with gold lung. This case suggests that the presence of activated lymphocytes against gold in the lung is cumulative, and that cell-mediated hypersensitivity is related to gold lung.

Arthritis, Rheumatoid↗
PubMed1987

Streptococcal protein G-gold complex: comparison with staphylococcal protein A-gold complex for spot blotting and immunolabeling.

Protein G, a cell wall protein isolated from human group G streptococci strain G148, binds in a similar manner as protein A from Staphylococcus aureus to the Fc portion of IgG molecules. Indeed, protein G has been proposed as a superior Fc binding protein due to its broader species reactivity. Thus, we have prepared a complex of protein G with particles of colloidal gold and determined its applicability for spot-blot analysis and postembedding immunolabeling by comparing it with protein A-gold complex. By spot-blot analysis no difference in binding of protein G-gold or protein A-gold to IgG molecules from a whole spectrum of animal species was observed. Moreover, using rabbit, sheep, or goat anti-rat albumin antibodies to detect nitrocellulose-immobilized rat albumin or antigenic sites in paraffin and Lowicryl K4M thin sections from rat liver, no difference was found with protein G-gold or protein A-gold. Similarly, no difference in binding to protein G-gold or protein A-gold was observed with a battery of monoclonal antibodies. However, in contrast to expectations, protein A-gold reacted well with both sheep and goat IgG molecules; indeed, for the light and electron microscopic localization of albumin with sheep or goat antibodies it was as efficient as protein G-gold. These results demonstrate, therefore, that both protein G-gold and protein A-gold are useful second step reagents for immunolabeling and that protein G-gold was not a superior probe in the systems tested.

Albumins↗
PubMed1984

[Intracellular gold content of circulating blood cells using various gold compounds].

Evidence on the action mechanisms of gold salts in the treatment of rheumatoid arthritis is still inconclusive. The intracellular localization of the place of action is likely. Therefore not only the serum gold levels but also the intracellular concentration of gold are of special interest. We measured the gold concentration in the serum and in the blood cells after in vitro application of aurothiomalate (Tauredon), gold keratinate (Auro-Detoxin) and triethylphosphine-gold (Ridaura) and in blood samples of patients undergoing these gold salts treatments. Cell-bound concentrations were found to vary extensively as a function of the gold compound used. While no or very little gold was present intracellularly after administration of the 2 parenteral drugs, up to 40% of the circulating gold was found to bind to the cells after administration of the triethylphosphine compound for gastro-intestinal absorption. The red cell concentration was more or less the same as that in the extracellular compartment. Gold apparently accumulated in the white cells, because the cell-bound concentration relative to unit volume was up to 20 times higher than the plasma level. The method used did not offer any information on the actual binding site of gold in white cells, i.e. cytoplasm versus nucleus versus cell membrane.

Anti-Inflammatory Agents↗
PubMed1989

Factors affecting efficiency of colloidal gold staining: pH-dependent stability of protein-gold conjugates.

The preparation of stable protein-gold conjugates is important in the quantitative colloidal gold staining. The protein adsorption onto colloidal gold particles and pH-dependent stability of protein-gold conjugates were examined using albumin and fibrinogen as model proteins. Albumin stabilized gold sols at pH values higher than 5.0. The amount of albumin necessary to stabilize gold sols was lowest at pH 5.6 and slightly increased as the pH of the adsorption medium was increased. Albumin was also able to stabilize gold particles even at acidic pH values ranging from 3.5 to 4.5, if a sufficient amount of albumin was added. Stable fibrinogen-gold conjugates were obtained at pH values above 6.5. Unlike albumin, the same amount of fibrinogen was able to stabilize gold sols as pH was increased from 7 to 10. The stability of the prepared protein-gold conjugates was very sensitive to the pH of the storing medium. The protein-gold conjugates were least stable at the isoelectric pH of the protein. The results suggest that protein-gold conjugates should be prepared at pH where conjugates are most stable, instead of pH close to the isoelectric point.

Colloids↗
PubMed1989

Probe size and bound label conformation in colloidal gold-ligand labels and gold-immunolabels.

Colloidal gold can be produced in sizes ranging from 1.0nm to 150nm. All sizes of gold can be conjugated, principally by hydrophobic bonding, to a variety of molecules including ligands, enzymes and antibodies, as well as lectins and polysaccharides. The activity of most of these biological molecules is retained on conjugation with gold particles irregardless of size range, although the ratio of protein surface area to gold particle surface area varies widely depending on particle and protein size. We have employed low voltage high resolution scanning electron microscopy to compare, microscopically, the shapes of biological molecules unbound, bound to very small (3nm) gold particles, and bound to larger (18nm-30nm) gold particles. When very small gold particles are conjugated to large protein molecules, several particles bind along the length of each molecule, while smaller protein molecules often wrap around a single small gold particle. With larger gold particles, several biological molecules bind to a single gold particle. In addition, the shape of protein molecules bound to larger gold particles differs from that of molecules bound to small gold particles.

Animals↗
PubMed1995

Skin testing with gold sodium thiomalate and gold sodium thiosulfate.

Recently gold sodium thiosulfate was found to be the most common sensitizer after nickel sulfate in our routinely patch tested dermatitis patients. When patients hypertensive to gold sodium thiosulfate were tested with another monovalent gold salt, gold sodium thiomalate, at equimolar concentrations, in principle, no positive reactions were obtained. Gold sodium thiomalate is used for treatment of rheumatoid arthritis, a treatment with a high frequency of adverse skin reactions. To investigate whether the reactivity difference between the 2 gold salts was due to differences in bioavailability, some experiments were carried out. Intracutaneous tests with the 2 gold salts at equimolar concentrations yielded equivalent reactions. When the concentration of gold sodium thiomalate for epicutaneous testing was increased, all 12 gold-allergic patients reacted positively. Therefore, in our department, contact allergy to gold sodium thiomalate is probably as common as contact allergy to gold sodium thiosulfate.

Administration, Cutaneous↗
PubMed1999

Hypersensitivity to gold in gold sodium thiomalate-induced dermatosis.

Gold compounds are widely used in the treatment of rheumatoid arthritis. Mucocutaneous side-effects leading to the discontinuation of medication are common with these drugs. We investigated whether allergic mechanisms are involved in dermatosis induced by gold sodium thiomalate (GSTM). Thirteen gold dermatosis patients, 15 arthritis patients without any side-effects from GSTM and 11 healthy controls participated in the study. Venous blood lymphocytes from these subjects were cultured with GSTM and gold sodium thiosulphate (GSTS) in the lymphocyte proliferation test (LPT). In some cases, interferon-gamma-producing cells were enumerated in vitro (T-cell ELISpot). The subjects were also patch-tested with GSTM and GSTS. The LPT to either GSTM, GSTS or both was positive in 12 of 13 patients with gold dermatosis. In the arthritis patient group without side-effects from gold, the LPT gave two false-positive results and in the healthy control group the LPT was falsely positive with one subject. T-cell ELISpot was positive in four of six gold dermatosis patients and negative in the arthritis and healthy control groups. Only one patient who also developed contact dermatitis from gold jewellery was positive to gold in the patch test. These results indicate that gold dermatosis is mediated, at least in part, by allergic mechanisms and that the LPT is of value in the diagnosis of gold dermatosis.

Adult↗
PubMed2002

Contact allergy to gold is correlated to dental gold.

Questionnaire studies have indicated that patients with dental gold will more frequently have contact allergy to gold. This study aimed at investigating the relationship between contact allergy to gold and the presence and amount of dental gold alloys. A total of 102 patients were referred for patch testing because of suspicion of contact allergy. Patch tests were performed with gold sodium thiosulphate 2% and 5%. The patients underwent an oral clinical and radiological examination. Contact allergy to gold was recorded in 30.4% of the patients, and of these 74.2% had dental gold (p=0.009). A significant correlation was found between the amount of gold surfaces and contact allergy to gold (p=0.008), but there was no statistical relationship to oral lesions. It is concluded that there is a positive relationship between contact allergy to gold and presence and amount of dental gold alloys.

Adult↗