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PubMed2004

Electrochemical redox control of ferrocene using a supramolecular assembly of ferrocene-linked C(60) derivative and metallooctaethylporphyrin array on a Au(111) electrode.

Supramolecular assembled layers of ferrocene-linked C(60) derivative (C(60)Fc) and various metal ions coordinated to octaethylporphyrin (MOEP) were formed on the surface of a Au(111) single-crystal electrode by immersing the Au substrate successively into a benzene solution containing MOEP and one containing C(60)Fc molecules. The MOEPs used were zinc(II) (ZnOEP), cobalt(II) (CoOEP), copper(II) (CuOEP), and iron(III) chloride (FeClOEP) of OEP (2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphine). The molecules of C(60)Fc directly attached to the Au(111) electrode showed poorly defined electrochemical redox response, whereas a clear electrochemical redox reaction of the ferrocene group in the C(60)Fc molecule was observed at 0.78 V versus reversible hydrogen electrode on ZnOEP, CoOEP, and CuOEP adlayers, but not on the FeClOEP adlayer. Adlattices of the underlying layer and the top layer of C(60)Fc were determined by in situ scanning tunneling microscopy. Adlayer structures of MOEP were independent of the central metal ion; that is, MOEP molecules were arranged hexagonally with two different orientations. Highly ordered C(60)Fc arrays were formed with 1:1 composition on the ZnOEP-, CoOEP-, and CuOEP-modified Au(111) surface, whereas a disordered structure of C(60)Fc was found on the FeClOEP-modified Au(111) surface. The presence of Cl ligand was found to prevent the formation of supramolecularly assembled layers with C(60)Fc molecules, resulting in an ill-defined unclear electrochemical response of the Fc group. The well-defined electrochemical response of the Fc group in C(60)Fc was clearly due to the control of orientation of C(60)Fc molecules.

Electrochemistry↗
PubMedDate not supplied

Subcorneal pustular dermatosis-type IgA pemphigus induced by thiol drugs.

We report a case of subcorneal pustular dermatosis (SPD)-type IgA pemphigus arising in a 49 year-old woman with rheumatoid arthritis who had been treated with chrysotherapy. Scaly erythemic plaques containing vesicles and pustules occurred on her chest and abdomen during the course of anti-rheumatic treatments using prednisolone at 11 mg/day and thiol compounds (bucillamine and gold sodium thiomalate). Histological investigations revealed subcorneal pustules containing many neutrophils and a few acantholytic cells, and intercellular IgA deposits at the upper epidermis of the eruptions without any other immunoglobulins and complement component C3. Circulating IgA antibodies directed against intercellular spaces of the epidermis were found by prolonged incubation of normal skin specimens in medium containing 20% patient's serum in an explant culture, although standard indirect immunofluorescence for IgA antibodies was negative. The eruptions were treated successfully with prednisolone, 30 mg/day, dapsone, 50 mg/day, and discontinuance of the thiol compound. In addition to the coexistent rheumatoid arthritis, both thiol compounds might have been responsible for the development of the eruptions.

Abdomen↗
PubMed2001

Two-, three-, and four-coordination at gold(I) supported by the bidentate selenium ligand [Ph2P(Se)NP(Se)Ph2](-).

Treatment of the gold(I) halide complexes LAuCl (L = PMe3, PPh3, CNC6H3Me2-2,6) with K[Ph2P(Se)NP(Se)Ph2] provides the gold-selenium coordination compounds [(N(Ph2PSe)2-Se,Se')AuL]. However, on standing for a number of days, the complex [(N(Ph2PSe)2-Se,Se')AuPMe3] gains a phosphine to provide the bis(phosphine) species [(N(Ph2PSe)2-Se,Se')Au(PMe3)2]. Treatment of the K[Ph2P(Se)NP(Se)Ph2] ligand with [(Ph3PAu)3O]BF4 allows the isolation of [(N(Ph2PSe)2-Se,Se')(AuPPh3)2]BF4. Reaction of the complex [(dppm)(AuCl)2] with AgSO3CF3 followed by addition of the ligand K[Ph2P(Se)NP(Se)Ph2] results in the formation of [(N(Ph2PSe)2-Se,Se')Au2(dppm)]OSO2CF3 and treatment of [(tht)AuCl] (tht = tetrahydrothiophene) with an equimolar quantity of K[Ph2P(Se)NP(Se)Ph2] affords the complex [(N(Ph2PSe)2-Se,Se')2Au2]. The compounds [(N(Ph2PSe)2-Se,Se')Au2(dppm)]OSO2CF3, [(N(Ph2PSe)2-Se,Se')AuPPh3] and [(N(Ph2PSe)2-Se,Se')Au(PMe3)2] have been investigated crystallographically. The results reveal that the metal centers are two-, three-, and four-coordinate, respectively. The cationic, eight-membered ring complex bearing the dppm ligand displays transannular aurophilic bonding and is further associated into dimers via intermolecular gold-selenium contacts. The six-membered rings in the other two structures have C2-symmetrical twist conformations, however, the Au(I) coordination sphere in [N(PPh2Se)2]AuPPh3 is not fully symmetrical. The Au-Se bond lengths increase dramatically as the coordination number of the metal atom becomes larger.

Journal Article↗
PubMed2005

Geochemical modeling of gold precipitation conditions in the Bloco do Butiá Mine, Lavras do Sul/Brazil.

A geochemical modeling of gold deposition was performed using the EQ3/EQ6 software package using conditions inferred from geological, petrographic, geochemical and fluid inclusion data from the Bloco do Butiá gold mine, Lavras do Sul, RS. Gold in the mine occurs only in the pyrite structure (invisible gold). The pyrite occurs associated with white mica (phengite) in the zone of phyllic alteration. The process of gold deposition showed to be related to temperature and pH decrease. The pH decrease was fundamental to gold deposition by destabilization of sulfur species [Au(HS)2- , HAu(HS)2(0) and Au(HS)0] dissolved in the aqueous solution, being Au(HS)0 the main gold transporting complex. The addition of KCl is hard to accept as cause of gold precipitation because no Cl- was detected in phengite. However, the geochemical mass balance calculation resulted in the gain of some potassium in the zone of phyllic alteration. The precipitation of pyrite (+/- auriferous) may have been strongly influenced by iron availability resulting from dissolution of ferrous chlorites by the fluids responsible for phengite deposition. The low salinity in quartz grain fluid inclusions from the propylitized wall rock also indicates the little importance of chlorine as gold transporting agent. Sulfur, and not chlorine, compounds must have dominated the gold transporting complexes in the Bloco do Butiá gold area.

Journal Article↗
PubMed1985

Antidotes for gold (sodium bis[thiosulfato]gold[I]) intoxication in mice.

Eight compounds were examined to determine their relative efficacy as antidotes in acute gold intoxication in mice after the intraperitoneal injection of 200 mg/kg of Na3 [Au(S2O3)2] X 2H2O. Of the compounds examined, 2,3 dimercaptosuccinic acid was the most effective antidote. It was noted that with D-penicillamine those animals which did not survive died sooner (in a matter of hours) than the corresponding control animals which had received no antidote (about 3 days). In subsequent experiments in which Na3 [Au(S2O3)2] X 2H2O was administered at the lower level of 140 mg/kg, 2,3 dimercaptosuccinic acid showed itself to be capable of reducing kidney gold levels by a factor of about 5 and liver gold levels by a factor of approximately 2.

Animals↗
PubMed2000

Xenon as a complex ligand: the tetra xenono Gold(II) cation in AuXe(4)2+(Sb(2)F(11)-)(2).

The first metal-xenon compound with direct gold-xenon bonds is achieved by reduction of AuF(3) with elemental xenon. The square planar AuXe(4)2+ cation is established by a single-crystal structure determination, with a gold-xenon bond length of approximately 274 picometers. The bonding between gold and xenon is of the final sigma donor type, resulting in a charge of approximately 0.4 per xenon atom.

Journal Article↗
PubMed2002

Attachment of alkyltrichlorosilanes to the terminal 3,5-dihydroxyphenyl moiety of a self-assembled thiol monolayer on gold.

The synthesis of 5-(6-mercaptohexyloxy)-1,3-dihydroxybenzene and the formation of a self-assembled monolayer on polycrystalline gold using this compound are described. Methyltrichlorosilane and (tridecafluoro-1,1,2,2-tetrahydrooctyl)trichlorosilane were attached to the 3,5-dihydroxyphenyl terminus of the monolayer. The modified surfaces were studied by contact angle measurement, XPS, and cyclic voltammetry. High contact angles of 119 degrees -128 degrees were observed for the semifluoroalkylsilyl-functionalized monolayer. These high contact angles were maintained after subjecting the surface to, e.g., boiling in water or heating in air to 300 degrees C. Characterization of the silane-modified monolayers by XPS indicated more than one layer of silane present at the top of the monolayer. The thickness was reduced after boiling the cross-linked monolayers in H(2)O, however, maintaining high contact angles. Cyclic voltammetry studies revealed that the semifluoroalkylsilyl-functionalized surface showed a higher blocking capability and a higher electrochemical stability than the parent monolayer.

Journal Article↗
PubMed2007

Monolayers at solid-solid interfaces probed with infrared spectroscopy.

The sensitivities of infrared spectra of thin adsorbate layers measured in either transmission, internal reflection or external reflection can be greatly increased if a light incidence medium with a high refractive index such as an IR-transparent solid material is used. This increase in sensitivity is due to the strong enhancement of the perpendicular electric field in a thin layer of low refractive index sandwiched between two high refractive index materials. Based on model calculations of a hypothetical sample layer, the influence and optimization of experimental parameters such as incidence angle, sample layer thickness and optical contact between layers are investigated. Under optimized conditions, this enhancement can exceed a factor of 100 when compared to conventional surface IR techniques. In addition, the spectra of sandwiched sample layers are governed by a uniform surface selection rule, such that only the perpendicular vibrational components are enhanced, and they permit a straightforward, substrate-independent analysis of surface orientations. Experimental examples of monolayer spectra of long-chain hydrocarbon compounds adsorbed onto gold and silicon substrates and contacted with a germanium crystal used as the incidence medium demonstrate the simple experimental realization and unprecedented sensitivity of this sandwich technique, and they offer novel insights into the chemistry and structure of monolayers confined and compressed between two solid surfaces.

Journal Article↗
PubMed2000

Methotrexate use in rheumatoid arthritis. A Clinician's perspective.

Aminopterine, a precursor of methotrexate (MTX), was first used for the treatment of rheumatoid arthritis (RA) in 1951 [Gubner, R., 1951. Therapeutic suppression of tissue reactivity: I. Comparison of the effects of cortisone and aminopterin. Am. J. Med. Sci. 221, 169-175; Gubner, R., August, S., Ginsberg, V., 1951. Therapeutic suppression of tissue reactivity: II. Effect of aminopterin in rheumatoid arthritis and psoriasis. Am. J. Med. Sci. 221, 176-182.]. Corticosteroids, and to some extent cyclophosphamide, took MTX out of the rheumatologist's armamentarium until the late 1970s-early 1980s when the toxic profile of these compounds became apparent. By the mid 1980s, four randomized clinical trials (RCTs) had proven beyond doubt the beneficial effects of MTX when administered to patients with established disease who had failed to respond to other compounds such as gold salts and D-penicillamine [Thompson, R.N., Watts, C., Edelman, J., Esdaile, J., and Russell, A.S., 1984. A controlled two-centre trial of parenteral methotrexate therapy for refractory rheumatoid arthritis. J. Rheumatol. 11, 760-763; Andersen, P.A., West, S.G., O'Dell, J.R., Via, C.S., Claypool, R.G., and Kotzin, B.L., 1985. Weekly pulse methotrexate in rheumatoid arthritis. Clinical and immunologic effects in a randomized, double-blind study. Ann. Intern. Med. 103, 489-496; Weinblatt, M.E., Coblyn, J.S., Fox, D.A., Fraser, P.A., Holdsworth, D.E., Glass, D.N., and Trentham, D.E., 1985. Efficacy of low-dose methotrexate in rheumatoid arthritis. N. Engl. J. Med. 312, 818-822; Williams, H.J., Willkens, R.F., Samuelson, C.O.J., Alarcón, G.S., Guttadauria, M., Yarboro, C., Polisson, R.P., Weiner, S.R., Luggen, M.E., Billingsley, L.M., Dahl, S.L., Egger, M.J., Reading, J.C., and Ward, J.R., 1985. Comparison of low-dose oral pulse methotrexate and placebo in the treatment of rheumatoid arthritis. A controlled clinical trial. Arthritis Rheum. 28, 721-730.]. Subsequently, these four trials were included in a meta-analysis and the drug was approved by the Food and Drug Administration for use in RA [Health and Public Policy Committee, H.P.P.C. and American College Physicians, A.C.P., 1987. Methotrexate in rheumatoid arthritis. Ann. Intern. Med. 107, 418-419; Paulus, H.E., 1986. FDA Arthritis Advisory Committee meeting: Methotrexate; guidelines for the clinical evaluation of antiinflammatory drugs; DMSO in scleroderma. Arthritis Rheum. 29, 1289-1290; Tugwell, P., Bennett, K., and Gent, M., 1987. Methotrexate in rheumatoid arthritis. Indications, contraindications, efficacy, and safety. Ann. Intern. Med. 107, 358-366.]. Since then, rheumatologists have become aware of what Pincus et al. have called "the side effects" of RA comparing the morbidity and mortality caused by RA with that potentially caused by medications used to treat this disease [Pincus, T. and Callahan, L.F., 1993. The "side effects" of rheumatoid arthritis: joint destruction, disability and early mortality. Br. J. Rheumatol. 32, 28-37.]. Thus, during the 1990s the use of MTX for the treatment of RA became generalized [O'Dell, J.R., 1997. Methotrexate use in rheumatoid arthritis. Rheum. Dis. Clin. N Am. 23, 779-796 (a); Bannwarth, B., Vernhes, J., Schaeverbeke, T., and Dehais, J., 1995. The facts about methotrexate in rheumatoid arthritis. Rev. Rhum. 62, 471-473 (b); Bologna, C., Jorgensen, C., and Sany, J., 1997a. Methotrexate as the initial second-line disease modifying agent in the treatment of rheumatoid arthritis patients. Clin. Exp. Rheumatol. 15, 597-601; Bologna, C., Viu, P. (ABSTRACT TRUNCATED)

Animals↗
PubMed2004

Quasi-relativistic density functional study of aurophilic interactions.

Fifteen molecules containing the Au(I) species have been calculated by ab initio HF and MP2 methods and by five different density functional approaches. The aurophilic Au(d10)-Au(d10) bonding mechanism has been investigated. Both, one-electron interactions (i.e., electrostatic, polarization, charge transfer, and orbital interference) and two-electron effects (i.e., correlation, dispersion) contribute significantly to the so-called 'secondary' or metallophilic bonds representing the Au-Au interaction. Second, the applicability of density functional approaches to this type of bonding has been tested. It is well-known that present day density functionals are not yet designed to simulate the long-range London dispersion forces between nonoverlapping systems, whereas they approximately reproduce the short range dynamical electron correlations of strongly overlapping chemically bonded nondegenerate species. It is found here empirically for the investigated groups of gold(I) cluster compounds that simple local density functionals (LDF) of the Slater (or Slater plus Vosko) type yield rather reasonable estimates for the equilibrium distances, and (on the average) also for the aurophilic interaction energies, though with rather large standard deviations. Still LDF are useful for survey investigations of Au cluster compounds. Common gradient corrected DF are not recommended here, nor are the large core pseudopotentials for Au.

Journal Article↗
PubMed2006

Direct and efficient stereological estimation of total cell quantities using electron microscopy.

Stereological estimation of total subcellular quantities in bioscience is presented in this report. Special emphasis is placed on the use of electron microscopy, which under certain circumstances may be combined with light microscopy. Three strategies based on the Cavalieri principle, the disector and local stereological probes through arbitrarily fixed points for estimation of total quantities inside cells are presented. The quantities comprise (total) number, length, surface area, volume or 3D spatial distribution for organelles as well as total amount of gold particles, various compounds or certain cytochemical markers.

Animals↗
PubMed1991

Thiol-containing compounds inhibit the production of monocyte/macrophage-derived angiogenic activity.

Macrophage (M phi)-mediated angiogenesis is believed to play an important role in the pathogenesis of rheumatoid arthritis. Gold sodium thiomalate, which is used in the treatment of rheumatoid arthritis, is a potent inhibitor of the production of m phi-derived angiogenic activity. To determine the mechanism of this inhibition, we studied the effects of thiol containing compounds (TCCs) on elicited mouse peritoneal m phi and lipopolysaccharide stimulated normal human monocytes. Monocyte/m phi conditioned media were potently angiogenic when assayed in rat corneas, while conditioned media from viable monocyte/m phi s treated with TCCs (at concentrations of 8.3-16.6 x 10(-5) M) were not. TCCs inhibited production of angiogenic activity by the m phi s rather than affecting other components of the angiogenic response such as the angiogenic factors or the target microvasculature of the rat cornea. Levels of the angiogenic mediator tumor necrosis factor-alpha (TNF-alpha) were not decreased in conditioned media of monocyte/m phi s treated with TCCs. We conclude that TCCs are potent inhibitors of the production of m phi-mediated angiogenic activity. This action of TCCs on m phi s may be in part responsible for the mechanism of action of therapeutic gold compounds in rheumatoid arthritis.

Animals↗