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PubMed2006

Resonance Rayleigh-scattering method for the determination of proteins with gold nanoparticle probe.

Gold nanoparticles with a 12-nm diameter were used as probes for the determination of proteins by resonance Rayleigh-scattering techniques. In weak acidic solution, large amounts of citrate anions will self-assemble on the surface of positively charged gold nanoparticles to form supermolecular compounds with negative charges. Below the isoelectric point, proteins with positive charges such as human serum albumin (HSA), bovine serum albumin (BSA), and ovalbumin (Ova) can bind gold nanoparticles to form larger volume products (the diameter of the binding product of gold nanoparticles with HSA is 23 nm.) through electrostatic force, hydrogen bonds, and hydrophobic effects, which can result in a red shift of the maximum absorption wavelength, the remarkable enhancement of the resonance Rayleigh-scattering intensity (RRS), and the appearance of the RRS spectra. At the same time, the second-order-scattering (SOS) and frequency-doubling-scattering (FDS) intensities are also enhanced. The binding products of gold nanoparticles with different proteins have similar spectral characteristics and the maximum wavelengths are located near 303 nm for RRS, 540 nm for SOS, and 390 for FDS, respectively. The scattering enhancement (DeltaI) is directly proportional to the concentration of proteins. Among them, the RRS method has the highest sensitivity and the detection limits are 0.38 ng/ml for HSA, 0.45 ng/ml for BSA, and 0.56 ng/ml for Ova, separately. The methods have good selectivity. A new RRS method for the determination of trace proteins using a gold nanoparticle probe has been developed. Because gold nanoparticle probes do not need to be modified chemically in advance, the method is very simple and fast.

Animals↗
PubMed2006

Development of a high analytical performance-tyrosinase biosensor based on a composite graphite-Teflon electrode modified with gold nanoparticles.

The design of a new tyrosinase biosensor with improved stability and sensitivity is reported. The biosensor design is based on the construction of a graphite-Teflon composite electrode matrix in which the enzyme and colloidal gold nanoparticles are incorporated by simple physical inclusion. Experimental variables such as the colloidal gold loading into the composite matrix, the enzyme loading and the potential applied to the bioelectrode were optimized. The Tyr-Au(coll)-graphite-Teflon biosensor exhibited suitable amperometric responses at -0.10 V for the different phenolic compounds tested (catechol; phenol; 3,4-dimethylphenol; 4-chloro-3-methylphenol; 4-chlorophenol; 4-chloro-2-methylphenol; 3-methylphenol and 4-methylphenol). The limits of detection obtained were 3 nM for catechol, 3.3 microM for 4-chloro-2-methylphenol, and approximately 20 nM for the rest of phenolic compounds. The presence of colloidal gold into the composite matrix gives rise to enhanced kinetics of both the enzyme reaction and the electrochemical reduction of the corresponding o-quinones at the electrode surface, thus allowing the achievement of a high sensitivity. The biosensor exhibited an excellent renewability by simple polishing, with a lifetime of at least 39 days without apparent loss of the immobilized enzyme activity. The usefulness of the biosensor for the analysis of real samples was evaluated by performing the estimation of the content of phenolic compounds in water samples of different characteristics.

Biosensing Techniques↗
PubMed2000

A gold(I) mononuclear complex and its association into binuclear and cluster compounds by hydrogen bonding or metal ion coordination.

The mononuclear Au(I) complex, Au(Spy)(PPh2py) (1), has been synthesized and characterized structurally. The complex possesses the expected linear coordination geometry with a S-Au-P bond angle of 176.03(6) degrees and no evidence of aurophilic interactions between nearest neighbor Au(I) ions in the solid state. Protonation of the pendant pyridyl groups of 1 leads to the formation of the H-bonded dimer [(Au(SpyH)(PPh2py))2](PF6)2 (2), which has also been structurally characterized. A linear coordination geometry at the Au(I) ions in 2 with a S-Au-P bond angle of 173.7(2) degrees is augmented by evidence of a strong aurophilic interaction with a Au...Au distance of 2.979(1) A. The pendant pyridyl groups of 1 have also been used to bind Cu(I) by reactions with [Cu(NCMe)4](PF6) and Cu(P(p-tolyl)3)2(NO3) leading to the formation of the heterobimetallic complexes [(AuCu(mu-Spy)(mu-PPh2py))2](PF6)2 (3) and [AuCu(P(p-tolyl)3)2(mu-Spy)(mu-PPh2py)](NO3) (4), respectively. A structure determination of 3 reveals a tetranuclear complex composed of two AuCu(mu-Spy)(mu-PPh2py)+ units held together by bridging thiolate ligands. A strong metal-metal interaction is noted between the two different d10 ions with nearest Au-Cu distances averaging 2.6395 A. The S-Au-P bond angles in 3 deviate slightly from linearity due to the Au...Cu interactions, while the coordination geometries at Cu(I) are distorted tetrahedral consisting of the two pyridyl nitrogen atoms, a bridging thiolate sulfur, and the interacting Au(I) ion. While mononuclear complex 1 is only weakly emissive in the solid state and in fluid solution, complexes 2-4 show stronger photoluminescence in the solid state and rigid media at 77 K, and in fluid solution. The emission maxima for 2-4 in ambient temperature fluid solution are 470, 635, and 510 nm, respectively. A tentative assignment of the emitting state as a S(p pi)-->Au LMCT transition is made on the basis of previous studies of Au(I) thiolate phosphine complexes. Shifts of lambda em result from the influence of H bonding or Cu(I) coordination on the filled thiolate orbital energy, or on the effect of metal-metal interaction on the Au(I) acceptor orbital energy. Crystal data for Au(Spy)(PPh2py) (1): triclinic, space group P1 (No. 2), with a = 8.3975(4) A, b = 11.0237(5) A, c = 12.4105(6) A, alpha = 98.6740(10) degrees, beta = 105.3540(10) degrees, gamma = 110.9620(10) degrees, V = 995.33(8) A3, Z = 2, R1 = 3.66% (I > 2 sigma(I)), wR2 = 9.04% (I > 2 sigma(I)) for 2617 unique reflections. Crystal data for [(Au(SpyH)(PPh2py))2](PF6)2 (2): triclinic, space group P1 (No. 2), with a = 14.0284(3) A, b = 14.1093(3) A, c = 15.7027(2) A, alpha = 97.1870(10) degrees, beta = 96.5310(10) degrees, gamma = 117.1420(10) degrees, V = 2692.21(9) A3, Z = 2, R1 = 7.72% (I > 2 sigma(I)), wR2 = 15.34% (I > 2 sigma(I)) for 5596 unique reflections. Crystal data for [(AuCu(mu-Spy)(mu-PPh2py))2](PF6)2 (3): monoclinic, space group P2(1)/c (No. 14), with a = 19.6388(6) A, b = 16.3788(4) A, c = 17.2294(5) A, beta = 91.48 degrees, V = 5540.2(3) A3, Z = 4, R1 = 3.99% (I > 2 sigma(I)), wR2 = 8.38% (I > 2 sigma(I)) for 10,597 unique reflections.

Journal Article↗
PubMed2006

Synthesis, structural characterization, and theoretical studies of gold(I) and gold(I)-gold(III) thiolate complexes: quenching of gold(I) thiolate luminescence.

The gold(I) thiolate complexes [Au(2-SC6H4NH2)(PPh3)] (1), [PPN][Au(2-SC6H4NH2)2] (2) (PPN = PPh3=N=PPh3), and [{Au(2-SC6H4NH2)}2(mu-dppm)] (3) (dppm = PPh2CH2PPh2) have been prepared by reaction of acetylacetonato gold(I) precursors with 2-aminobenzenethiol in the appropriate molar ratio. All products are intensely photoluminescent at 77 K. The molecular structure of the dinuclear derivative 3 displays a gold-gold intramolecular contact of 3.1346(4) A. Further reaction with the organometallic gold(III) complex [Au(C6F5)3(tht)] affords dinuclear or tetranuclear mixed gold(I)-gold(III) derivatives with a thiolate bridge, namely, [(AuPPh3){Au(C6F5)3}(mu2-2-SC6H4NH2)] (4) and [(C6F5)3Au(mu2-2-SC6H4NH2)(AudppmAu)(mu2-2-SC(6)H4NH2)Au(C6F5)3] (5). X-ray diffraction studies of the latter show a shortening of the intramolecular gold(I)-gold(I) contact [2.9353(7) or 2.9332(7) A for a second independent molecule], and short gold(I)-gold(III) distances of 3.2812(7) and 3.3822(7) A [or 3.2923(7) and 3.4052(7) A] are also displayed. Despite the gold-gold interactions, the mixed derivatives are nonemissive compounds. Therefore, the complexes were studied by DFT methods. The HOMOs and LUMOs for gold(I) derivatives 1 and 3 are mainly centered on the thiolate and phosphine (or the second thiolate for complex 2), respectively, with some gold contributions, whereas the LUMO for derivative 4 is more centered on the gold(III) fragment. TD-DFT results show a good agreement with the experimental UV-vis absorption and excitation spectra. The excitations can be assigned as a S --> Au-P charge transfer with some mixture of LLCT for derivative 1, an LLCT mixed with ILCT for derivative 2, and a S --> Au...Au-P charge transfer with LLCT and MC for derivative 3. An LMCT (thiolate --> Au(III) mixed with thiolate --> Au-P) excitation was found for derivative 4. The differing nature of the excited states [participation of the gold(III) fragment and the small contribution of sulfur] is proposed to be responsible for quenching the luminescence.

Crystallography, X-Ray↗
PubMed2006

Using triethynylphosphine ligands bearing bulky end caps to create a holey catalytic environment: application to gold(I)-catalyzed alkyne cyclizations.

The synthesis, properties and catalytic uses of phosphinoalkynes bearing bulky end caps at the alkyne termini, that is, tris[(triarylsilyl)ethynyl]phosphines are reported. The most salient feature of the new phosphines is the holey molecular shape possessing a deep and large-scale metal-binding cavity. The holey phosphines displayed remarkable rate enhancement in the gold(I)-catalyzed six- and seven-membered ring forming cyclizations of acetylenic keto esters and 1,7-enynes. It is proposed that the cavity in the ligand forces a nucleophilic center (enol or alkene) of the acetylenic compounds close to the gold-bound alkyne, making ring-closing anti attack feasible.

Acetylene↗
PubMed1988

Metabolism of mutagenic polycyclic aromatic hydrocarbons by photosynthetic algal species.

Polycyclic aromatic hydrocarbons (PAH) known to produce carcinogenic and mutagenic effects have been shown to contaminate waters, sediments and soils. While it is accepted that metabolites of these compounds are responsible for most of their biological effects in mammals, their metabolism, and to a large extent their bioactivity, in aquatic plants have not been explored. Cultures of photosynthetic algal species were assayed for their ability to metabolize benzo[a]pyrene (BaP), a carcinogenic PAH under conditions which either permitted (white light) or disallowed (gold light) photooxidation of the compound. Growth of Selenastrum capricornutum, a fresh-water green alga, was completely inhibited when incubated in white light with 160 micrograms BaP/l medium. By contrast concentrations at the upper limit of BaP solubility in aqueous medium had no effect on algal growth when gold light was used. BaP quinones and phenol derivatives were found to inhibit growth of Selenastrum under white light incubation. BaP phototoxicity and metabolism were observed to be species-specific. All 3 tested species of the order Chlorococcales were growth-inhibited by BaP in white light whereas neither the green alga Chlamydomonas reinhardtii nor a blue-green, a yellow-green or an euglenoid alga responded in this fashion. Assays of radiolabeled BaP metabolism in Selenastrum showed that the majority of radioactivity associated with BaP was found in media as opposed to algal cell pellets, that the extent of metabolism was BaP concentration dependent, and that the proportion of various metabolites detected was a function of the light source. After gold light incubation, BaP diols predominated while after white light treatment at equal BaP concentrations, the 3,6-quinone was found in the highest concentration. Extracted material from algal cell pellets and from media was tested for mutagenicity in a forward mutation suspension assay in Salmonella typhimurium using resistance to 8-azaguanine for selection. Direct-acting mutagens were detected in extracted media from incubation of Selenastrum with 400 micrograms BaP/l for 1 day in gold light. Extracts of media from algae incubated in gold light from 1 to 4 days with 1200 micrograms BaP/l were found to have direct-acting mutagens as well as those requiring further metabolism. Media extracts from white light incubations of BaP were mutagenic upon addition of rat liver homogenates. Activity of these materials from white light treatment are largely attributable to unmetabolized BaP.

Benzo(a)pyrene↗
PubMed1987

Reproducibility of results in "near-replicate" carcinogenesis bioassays.

Reproducibility of results was examined in 70 "near-replicate" comparisons consisting of 2 or more long-term carcinogenesis bioassays of the same chemical administered by the same route and using the same sex and strain of rodent. Overall, there was good reproducibility of positivity, target site, and carcinogenic potency in hamsters, mice, and rats. The published authors' opinions about whether the test was positive disagreed in only 9 of the 70 comparisons. Among the 35 comparisons in which all tests of the chemical were positive, 33 of the near-replicates had at least 1 identical target site. The carcinogenic potency values estimated from near-replicate tests in these 35 comparisons were within a factor of 2 of each other in 40% of the comparisons, within a factor of 5 in 80%, and within a factor of 10 in 90%. For the few cases in which the carcinogenic response was not reproduced, analyses suggest two explanations: In mice the discrepant cases tended to have shorter experiment times than average; in both rats and mice the discrepant results tended to be tests of weakly active compounds.

Animals↗
PubMed1996

Antitumor properties of some 2-[(dimethylamino)methyl]phenylgold(III) complexes.

Four analogues of the gold(III) complex [AuCl2(damp)] (1) (damp = 2-[(dimethylamino)methyl]phenyl) have been evaluated for antitumor activity. The compounds have structural features in common with cisplatin which was included as a comparison in the study. In vitro, against a panel of cell lines established from tumors of different tissue types, the gold complexes showed broadly similar growth inhibitory properties with some selectivity to the HT1376 bladder cell line. In a panel of human ovarian carcinoma cell lines, non-cross-resistance to cisplatin was observed, for the complexes, in an acquired cisplatin-resistant line. In vivo, using subcutaneously implanted xenografts derived from the HT1376 bladder and CH1 ovarian cell lines, [Au(acetato)2(damp)] (3) and [Au(malonato)(damp)] (5) (administered intraperitoneally) gave significant tumor inhibition. Mechanistic studies performed with compound 3 showed marked differences to cisplatin. Thus, much higher concentrations of the gold compound were required to affect Col E1 plasmid mobility, and an alkaline elution study showed that 3 did not cause interstrand DNA cross-links in SK-OV-3 cells. Exposure of SK-OV-3 cells to 3 induced only relatively minor changes in cell cycle distribution. Furthermore 3 was only marginally active in vivo against the cisplatin-sensitive murine ADJ/PC6 plasmacytoma. In summary, the gold-(III) complexes 3 and 5 exhibited selective cytotoxicity in vitro and showed in vivo antitumor activity against human carcinoma xenografts. Also, although 3 has some structural similarity to cisplatin, its mode of action appears to be different.

Animals↗
PubMed1979

The aurosome.

Aurosomes are lysosomal bodies containing gold. Colloidal gold produces aurosomes containing spherical electron-dense granules. Soluble gold salts produce aurosomes containing lamellar, filamentous and rod-like profiles studded with particles and granules. This morphological pattern is quite distinctive, and is not affected or altered by which particular soluble gold salt is administered, by which route it is administered or in which species or cell type the aurosome occurs. In the skin of patients treated with soluble gold salts the characteristics electron-dense formations indicating the presence of gold are often found in compound melanosomes and other lysosomes in the dermal macrophages; while in the synovial membrane these characteristic electron-dense deposits are seen in the numerous lysosomes that develop in the rheumatoid synovial membrane. Thus it would appear that while aurosomes may vary somewhat in morphology, the electron dense contents indicating the presence of gold have a fairly constant morphology.

Animals↗
PubMed2002

Induction of mitochondrial permeability transition by auranofin, a gold(I)-phosphine derivative.

1 Gold(I)-thiolate drugs are compounds that specifically interact with thiol and/or selenol groups and are essentially utilized in the treatment of rheumatoid arthritis. 2 Considering the importance of thiol groups in regulating mitochondrial membrane permeability, the effects of auranofin (S-triethylphosphinegold(I)-2,3,4,6-tetra-O-acetyl-1-thio-beta-D-glucopyranoside), a second-generation gold drug, were studied on mitochondria isolated from rat liver. 3 Auranofin, at submicromolar concentrations, was able to induce the mitochondrial membrane permeability transition observed as swelling and loss of membrane potential. Both events are completely inhibited by cyclosporin A, the specific inhibitor of mitochondrial permeability transition. Calcium ions and energization by succinate are required for the occurrence of permeability transition. 4 By interacting with the active site selenol group, auranofin results as an extremely potent inhibitor of mitochondrial thioredoxin reductase, both isolated and in its mitochondrial environment. 5 It is concluded that auranofin, in the presence of calcium ions, is a highly efficient inducer of mitochondrial membrane permeability transition, potentially referable to its inhibition of mitochondrial thioredoxin reductase.

Animals↗
PubMed2004

Synthesis and auration of primary and di-primary heteroaryl-phosphines.

Convenient high-yield syntheses of the primary and di-primary heteroaryl-phosphines R-PH2 and H2P-R'-PH2(with R = 2-thienyl, 2-furyl, and R'= 2,5-thiophenediyl, 2,5-furandiyl, respectively) are presented. The products and a set of precursor molecules have been characterized by analytical and spectral data, and the crystal structures of selected molecules have been determined: 2-C4H3O-PCl2, 2,5-(Cl2P)2C4H2O, 2,5-[(Et2N)2P]2C4H2E (with E = O, S). In the crystals, the two molecules with -PCl2 substituents adopt trans conformations, while the other two have the -P(NEt2)2 groups rotated into a twist conformation. The reaction of the thienyl compounds with tris[(tert-phosphine)gold]oxonium tetrafluoroborates gave almost quantitative yields of the tri- and hexanuclear gold complexes, respectively: {2-C4H3S-P[Au(PR3)]3}+BF4- and [2,5-{[(R3P)Au]3P}2C4H2S]2+(BF4(-)2, (R =tBu, Ph). The structures of the compounds with R3P =tBu3P ligands have been determined. In both cases the [2-C4H3/2S-P] units cap triangles of gold atoms in an array that can be described as three [Au(PR3)]+ cations bridged by a phosphido dianion (RP)2-.

Journal Article↗
PubMed2006

Computer-aided molecular design of highly potent HIV-1 RT inhibitors: 3D QSAR and molecular docking studies of efavirenz derivatives.

Ligand- and structure-based design approaches have been applied to an extended series of 74 efavirenz compounds effectively inhibiting wild type (WT) and mutant type (K103N) HIV-1 reverse transcriptase (RT). For ligand-based approach, three dimensional quantitative structure-activity relationship (3D-QSAR) methods, comparative molecular field analysis (CoMFA) and comparative similarity indices analysis (CoMSIA), were performed. The starting geometry of efavirenz was obtained from X-ray crystallographic data. The efavirenz derivatives were constructed and fully optimized by ab-initio molecular orbital method at HF/3-21G level. Reliable QSAR models for high predictive abilities were developed. Regarding WT and K103N inhibitions, CoMFA models with r2/cv = 0.651 and 0.678 and CoMSIA models with r2/cv = 0.662 and 0.743 were derived, respectively. The interpretation obtained from the models highlights different structural requirements for inhibition of WT and K103N HIV-1 RT. To elucidate potential binding modes of efavirenz derivatives in the binding pocket of WT and K103N HIV-1 RT, structure-based approach based on computational docking studies of selected efavirenz compounds were performed by using GOLD and FlexX programs. The results derived from docking analysis give additional information and further probe the inhibitor-enzyme interactions. The correlation of the results obtained from 3D QSAR and docking models validate each other and lead to better understanding of the structural requirements for the activity. Therefore, these integrated results are informative to provide key features and a helpful guideline for novel compound design active against HIV-1 RT.

Alkynes↗
PubMed2002

Enantioselective adsorption of phenylalanine onto self-assembled monolayers of 1,1'binaphthalene-2,2'-dithiol on gold.

Self-assembled monolayer of atropisomeric compound, 1,1'-binaphthalene-2,2'-dithiol (BNSH), provides a field for chiral discrimination. The two-dimensional chiral arrangement with screw-like units, each of which is composed of three BNSH molecules, plays an important role in the enantioselectivity of adsorption of phenylalanine, as revealed by a quartz crystal microbalance technique.

Adsorption↗