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Bin Su

Publications and source records attributed to Bin Su.

At least 19 recordsLinked to original sources
PubMed2006

CdSe sensitized thin aqueous films: probing the potential distribution inside multilayer assemblies.

Ultrathin polypeptide multilayer films are assembled by the sequential electrostatic adsorption of monolayers of poly-l-lysine and poly-l-glutamic acid onto carboxylic acid terminated alkanethiol-modified gold surfaces. The polypeptide multilayer films are hydrophilic, can incorporate electroactive species such as ferri/ferrocyanide, and are stable when immersed in organic solvents such as 1,2-dichloroethane. Cadmium selenide quantum dots stabilized by negatively charged citrate groups are electrostatically attached to the multilayer film assembly in order to act as photoactive species. Photocurrent responses originating from the CdSe sensitized ultrathin multilayer film are investigated as functions of the applied potential, the thickness of the film and the presence of quenchers in the organic phase. A theoretical model is proposed in order to analyze the kinetics of the photoinduced electron-transfer reactions and to probe the potential distribution within the film.

Journal Article↗
PubMed2006

Solvent effect on redox properties of hexanethiolate monolayer-protected gold nanoclusters.

The capacitance of monolayer-protected gold nanoclusters (MPCs), C(MPC), in solution has been theoretically reconsidered from an electrostatic viewpoint, in which an MPC is considered as an isolated charged sphere within two dielectric layers, the intrinsic coating monolayer, and the bulk solvent. The model predicts that the bulk solvent provides an important contribution to C(MPC) and influences the redox properties of MPCs. This theoretical prediction is then examined experimentally by comparing the redox properties of MPCs in four organic solvents: 1,2-dichloroethane (DCE), dichloromethane (DCM), chlorobenzene (CB), and toluene (TOL), in all of which MPCs have excellent solubility. Furthermore, this set of organic solvents features a dielectric constant in a range from 10.37 (DCE) to 2.38 (TOL), which is wide enough to probe the solvent effect. In these organic solvents, tetrahexylammonium bis(trifluoromethylsulfonyl)imide (THATf2N) is used as the supporting electrolyte. Cyclic and differential pulse voltammetric results provide concrete evidence that, despite the monolayer protection, the solvent plays a significant effect on the properties of MPCs in solution.

Journal Article↗
PubMed2006

Antioxidant redox sensors based on DNA modified carbon screen-printed electrodes.

Antioxidant redox sensors based on DNA modified carbon screen-printed electrodes were developed. The carbon ink was doped with TiO2 nanoparticles, onto which double-strand DNA was adsorbed. A redox mediator, namely, tris-2,2'-bipyridine ruthenium(II) [Ru(bpy)3(2+)] was electrooxidized on the electrode surface to subsequently oxidize both the adsorbed ds-DNA and the antioxidants in solution. The resulting oxidation damage of the adsorbed ds-DNA was then detected by square wave voltammetry in a second solution containing only Ru(bpy)3Cl2 at a low concentration (microM). A kinetic model was developed to study the protecting role of antioxidants in aqueous solutions. The electrochemical sensor has been applied to evaluate the redox antioxidant capacity of different molecules.

Antioxidants↗
PubMed2006

Novel sulfonanilide analogues suppress aromatase expression and activity in breast cancer cells independent of COX-2 inhibition.

Aromatase is a particularly attractive target in the treatment of estrogen receptor positive breast cancer. Aromatase levels in breast cancer cells are enhanced by prostaglandins and reduced by COX inhibitors. The synthesis and biological evaluation of a novel series of sulfonanilide analogues derived from the COX-2 selective inhibitor NS-398 are described. The compounds suppress aromatase enzyme activity in SK-BR-3 breast cancer cells in a dose- and time-dependent manner. The effect of these compounds on COX-2 inhibition is investigated in breast cancer cells as well. Structure-activity analysis does not find a correlation between aromatase suppression and COX-2 inhibition. Microsomal aromatase inhibition studies rule out the possibility of direct enzyme inhibition. Real-time PCR analysis demonstrates that the sulfonanilide analogues decrease aromatase gene transcription in SK-BR-3 cells. These studies suggest that the novel sulfonanilide compounds suppress aromatase activity and transcription in SK-BR-3 breast cancer cells independent of COX-2 inhibition.

Aniline Compounds↗
PubMed2006

2-Dimensional porphyrin self-assemblies at molecular interfaces.

The heterodimer formed by electrostatic association of zinc(II) meso-tetrakis(N-methylpyridyl)porphyrin (ZnTMPyP) and zinc(II) meso-tetrakis(p-sulfonatophenyl)porphyrin (ZnTPPS) exhibits a strong affinity for the interface between water and 1,2-dichloroethane (DCE). Surface tension measurements using the quasi-elastic light scattering (QELS) technique reveal that the heterodimer adsorption can be described in terms of a Langmuir isotherm with standard Gibbs energy of adsorption of -45.5 kJ mol(-1). The orientation of the heterodimer transition dipole moment, as estimated from light polarization modulated reflectance (LPMR), shows a marked dependence on the bulk concentration of heterodimer. On the other hand, changes in the Galvani potential difference between the two phases have little effect on the heterodimer organization at the water/1,2-dichloroethane interface when the surface coverage is close to maximum. This behavior suggests that the ZnTPPS-ZnTMPyP heterodimer forms an adsorbed layer of aggregated molecules which affects the physical properties of the interface. Indeed, capacitance and surface tension measurements reveal that the dielectric properties of the water/DCE interface are significantly altered in the presence of heterodimer species.

Journal Article↗
PubMed2006

Interference by naturally occurring fatty acids in a noncellular enzyme-based aromatase bioassay.

Natural product drug discovery efforts frequently utilize noncellular screening assays. Fatty acids are commonly found in natural product extracts, and some have been shown to interfere with noncellular assays. Several pure fatty acids were tested using a noncellular aromatase assay, with the unsaturated analogues showing strong inhibitory activity, while the saturated analogues were inactive. Unsaturated fatty acids were further tested against SK-BR-3 hormone-independent human breast cancer cells that overexpress aromatase and were found to be inactive. In natural product screening efforts, especially using plant seeds, it is recommended that extracts active in noncellular bioassays should be dereplicated for the presence of fatty acids prior to bioassay-guided fractionation.

Aromatase↗
PubMed2005

Redox properties of self-assembled gold nanoclusters.

The redox properties of a monolayer of alkanethiolate-protected gold nanoclusters (MPCs) constructed on a gold slide electrode was studied in 1,2-dichloroethane (DCE) electrolyte solutions. The influence of the electrostatic interaction between attached MPCs and the substrate electrode on the absolute standard redox potential of MPCs was theoretically considered and studied experimentally.

Alkanes↗
PubMed2005

Lead optimization of 7-benzyloxy 2-(4'-pyridylmethyl)thio isoflavone aromatase inhibitors.

Aromatase, the enzyme responsible for estrogen biosynthesis, is a particularly attractive target in the treatment of hormone-dependent breast cancer. The synthesis and biological evaluation of a series of 2-(4'-pyridylmethyl)thio, 7-alkyl- or aryl-substituted isoflavones as potential aromatase inhibitors are described. The isoflavone derivatives demonstrate IC(50) values from 79 to 553 nM and compete with the endogenous substrate, androstenedione. Data supporting the ability of these analogs to suppress aromatase enzyme activity in the SK-BR-3 breast cancer cell line are also presented.

Aromatase↗
PubMed2005

Reactivity of monolayer-protected gold nanoclusters at dye-sensitized liquid/liquid interfaces.

Hexanethiolate monolayer-protected gold nanoclusters (MPCs) were used as redox quenchers at the polarizable water/1,2-dichloroethane (DCE) interface. Photocurrent responses originating from the heterogeneous quenching of photoexcited water soluble porphyrin complexes by MPCs dissolved in the DCE phase were observed. As MPCs can function as both electron acceptors and donors, the photocurrent results from the superposition of two simultaneous processes, which correspond to the oxidation and reduction of MPCs. The magnitude of the net photocurrent is essentially determined by the balance of the kinetics of these two processes, which can be controlled by tuning the Galvani potential difference between the two phases. We show that, within the available potential window, the apparent electron-transfer rate constants follow classical Butler-Volmer dependence on the applied potential difference.

Journal Article↗
PubMed2005

Absolute standard redox potential of monolayer-protected gold nanoclusters.

The redox properties of monolayer-protected gold nanoclusters (MPCs) are considered from both the theoretical and experimental viewpoints. The "absolute standard redox potential" ([E0((z/z)-1))]abs) of MPCs is first derived from electrostatic considerations. A linear dependence of the absolute standard redox potential on the valence state of MPCs is theoretically predicted and verified experimentally. By employing ferricinium/ferrocene (Fc+/Fc) as a reference redox couple, the average valence state of MPCs at a given potential can be estimated.

Letter↗
PubMed2005

Synthesis and characterization of azole isoflavone inhibitors of aromatase.

The synthesis and biological evaluation of a series of 2-azole and 2-thioazole isoflavones as potential aromatase inhibitors are described. Differences in inhibitory activity of triazole and imidazole inhibitors are rationalized with density functional theory to expose a key difference in the electronic structure of these molecules. In addition, difference binding spectra of inhibitors to immunoaffinity-purified aromatase produces classical Type II spectra consistent with coordination of the nitrogen lone pair electrons to the aromatase P450 heme.

Androstenedione↗
PubMed2004

[Factors of avascular necrosis of femoral head and osteoporosis in SARS patients' convalescence].

OBJECTIVE: To explore the factors affecting the pathogenesis of avascular necrosis of femoral head and osteoporosis of SARS patients during convalescent stage. METHODS: The clinical data of 40 SARS patients, 12 males and 28 females, aged 29 +/- 9, hospitalized from April to June 2003, were reviewed, targeted on the use of glucocorticoids. Three months after the discharge ELISA and indirect immunofluorescent antibody (IFA) assay were used to detect the serum IgG. Magnetic resonance imaging (MRI) was used to detect the damage of the head of femur and quantitative ultrasound (QUS) was used to detect osteoporosis at the left heel. RESULTS: The average total dosage of methylprednisolone was (4949 +/- 2959) mg, and the average course of treatment was (24 +/- 5) days (16 to 30 days). Twenty-three patients underwent ictus therapy of corticosteroids for (8 +/- 4) days. The extenuation time of corticosteroid' dosage was (33 +/- 26) mg/d. Of the 40 patients, 36 were IgG positive with an average A value of (0.91 +/- 0.24) and 4 patients were IgG negative. Twelve patients (30%) were with type I avascular necrosis of femoral head, including 3 cases with unilateral left--necrosis and 9 cases of bilateral necrosis. The other 28 patients were without necrosis. Two patients were suffering from osteoporosis and 30 patients were with bone density decrement. The average Z values of the parameter BUA and VOS were (-1.26 +/- 0. 53) and (-0.53 +/- 0.30) respectively. The corresponding T values of the parameter BUA and VOS were (-1.49 +/- 0.59) and (-0.65 +/- 0.05) respectively. The influencing factors of femoral necrosis included the degree of healing activity, the dosage summation of corticosteroids, and length of ictus therapy. The influencing factors of bone density included age, dosage summation, and length of ictus therapy. The influencing factors of the bone fabric and flexibility included the use and length of ictus therapy. Statistics showed that serum IgG was not related with avascular necrosis of femoral head and osteoporosis. CONCLUSIONS: The incidence rates of avascular necrosis of femoral head and of osteoporosis were higher in convalescent SARS patients than in general population. The influencing factors of femoral necrosis included the degree of healing activity, the dosage summation of corticosteroids, and length of ictus therapy. The influencing factors of bone density included age, dosage summation, and length of ictus therapy. The influencing factors of the bone fabric and flexibility included the use and length of ictus therapy. Statistics showed that serum IgG was not related with avascular necrosis of femoral head and osteoporosis. SARS virus may not affect the pathogenesis of avascular necrosis of femoral head and osteoporosis.

Adolescent↗
PubMed2004

Reversible voltage-induced assembly of au nanoparticles at liquid/liquid interfaces.

The voltage-induced assembly of mercaptosuccinic acid-stabilized Au nanoparticles of 1.5 +/- 0.4 nm diameter is investigated at the polarizable water/1,2-dichloroethane interface. Admittance measurements and quasi-elastic laser scattering (QELS) studies reveal that the surface concentration of the nanoparticle at the liquid/liquid boundary is reversibly controlled by the applied bias potential. The electrochemical and optical measurements provide no evidence of irreversible aggregation or deposition of the particles at the interface. Analysis of the electrocapillary curves constructed from the dependence of the frequency of the capillary waves on the applied potential and bulk particle concentration indicates that the maximum particle surface density is 3.8 x 10(13) cm(-2), which corresponds to 67% of a square closed-pack arrangement. This system provides a unique example of reversible assembly of nanostructures at interfaces, in which the density can be effectively tuned by the applied potential bias.

Journal Article↗
PubMed2004

[The effect of curcumin on bladder cancer cell line EJ in vitro].

OBJECTIVE: To observe the effect of curcumin on bladder cancer cell line EJ in vitro. METHODS: Cell morphology, MTT, flow cytometer, immunocytochemical method for detecting NF-KB, Cyclin D1 were used to observe the effect of 5,10,20 mg/L curcumin on bladder cancer cell line EJ in vitro. RESULTS: All concentrations curcumin resulted in the growth suppression significantly [Suppression ratio > or = (27.5 + 3.1)%, P < 0.05]. Above 10 mg/L concentrations curcumin induced apoptosis [Apoptosis ratio > or = (14.6 +/- 1.8)%, P < 0.05] and down-regulated of the expression of NF-kappaB [Expression ratio < or = (35.8 +/- 4.2)%, P < 0.05], Cyclin D1 [Expression ratio < or = (29.7 +/- 3.2)%, P < 0.05]. The cell phase arrest induced by curcumin was G1 phase arrest mainly with significant decrease of S phase. CONCLUSIONS: Curcumin can suppress the growth, induce apoptosis of bladder cancer EJ cell in vitro. Its mechanism is related with down-regulations of the expressions of NF-kappaB and Cyclin D1. Curcumin has great potential for the treatment of bladder cancer.

Antineoplastic Agents↗
PubMed2003

Synthesis and potential antimetastatic activity of monovalent and divalent beta-D-galactopyranosyl-(1-->4)-2-acetamido-2-deoxy-D-glucopyranosides.

Anomers of monovalent and divalent beta-D-galactopyranosyl-(1-->4)-2-acetamido-2-deoxy-D-gluco-pyranosides were synthesized under different glycosylation conditions, and evaluated for in vitro antimetastatic activity. Three compounds showed promising inhibitory effects on cancer cell attachment, spreading, migration, and invasion.

Amino Sugars↗
PubMed2003

Cytoskeletal rearrangements in gastric epithelial cells in response to Helicobacter pylori infection.

Helicobacter pylori causes host epithelial cell cytoskeletal rearrangements mediated by the translocation and tyrosine phosphorylation of an outer-membrane protein, CagA, and by the vacuolating cytotoxin, VacA. However, the mechanisms by which H. pylori mediates cytoskeletal rearrangements in infected host cells need to be more clearly defined. The aim of this study was to determine the effects of H. pylori isolates from children on the architecture of host gastric epithelial cells. Gastric epithelial (AGS) cells were infected with type I (cagE(+), cagA(+), VacA(+)) H. pylori, a type II H. pylori strain (cagE(-), cagA(-), VacA(-)) or a cagE isogenic mutant. Double-labelled immune fluorescence was used to detect adherent H. pylori and the distribution of F-actin, alpha-actinin and Arp3. Both type I and type II H. pylori strains induced stress fibres in gastric epithelial cells that were not observed in uninfected cells. Type I H. pylori also induced cell elongation (hummingbird phenotype) after 4 h of infection, whereas the type II H. pylori strain did not. Less elongation occurred when AGS cells were exposed to a cagE isogenic mutant, compared with the parental strain. Confocal microscopy showed Arp3 accumulation in AGS cells infected with wild-type H. pylori, but not in response to infection with the cagE mutant. These findings indicate that type I H. pylori induce a stress fibre-like phenotype in infected gastric epithelia by a mechanism that is different from the induction of host-cell elongation. In addition to CagA and VacA, cagE also impacts on the morphology of infected gastric epithelial cells.

Actin-Related Protein 3↗
PubMed2003

Helicobacter pylori activates Toll-like receptor 4 expression in gastrointestinal epithelial cells.

Helicobacter pylori activates the transcription factor NF-kappaB, leading to proinflammatory cytokine production by gastric epithelial cells. However, the receptors for the initial bacterial interaction with host cells which activate downstream signaling events have not been completely defined. Recently, it has been shown that microbial components activate Toll-like receptors (TLRs), thereby leading to AP-1- and NF-kappaB-dependent transcription and resulting in the production of proinflammatory cytokines. The aim of this study was to determine whether H. pylori activates TLR4. Reverse transcription-PCR showed that both type I and type II H. pylori clinical isolates induced TLR4 mRNA expression in AGS cells compared with that by uninfected controls. H. pylori upregulated TLR4 protein expression in two gastric epithelial cell lines (AGS and MKN45) and one intestinal epithelial cell line (T84). Monoclonal TLR4 antibody inhibited lipopolysaccharide-induced interleukin-8 secretion from THP-1 macrophages but not from gastric epithelial cells infected with H. pylori. H. pylori demonstrated increased adherence to CHO TLR4-transfected cells compared with that to both CHO TLR2-transfected and nontransfected CHO cells (P < 0.01). These results indicate that H. pylori activates TLR4 expression in epithelial cells and that TLR4 can serve as a receptor for H. pylori binding.

Animals↗