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Biomedical subjects

Yongsheng Chen

Publications and source records attributed to Yongsheng Chen.

16 recordsLinked to original sources
PubMed2006

Enhanced bioaccumulation of cadmium in carp in the presence of titanium dioxide nanoparticles.

In this study adsorption of Cd onto TiO2 nanoparticles and natural sediment particles (SP) were studied and the facilitated transports of Cd into carp by TiO2 nanoparticles and SP were assessed by bioaccumulation tests exposing carp (Cyprinus carpio) to Cd contaminated water in the presence of TiO2 and SP respectively. The results show that TiO2 nanoparticles had a significantly stronger adsorption capacity for Cd than SP. The presence of SP did not have significant influence on the accumulation of Cd in carp during the 25 d of exposure. However, the presence of TiO2 nanoparticles greatly enhanced the accumulation of Cd in carp. After 25 d of exposure Cd concentration in carp increased by 146%, and the value was 22.3 and 9.07 microg/g, respectively. And there is a positive correlation between Cd and TiO2 concentration. Considerable Cd and TiO2 accumulated in viscera and gills of the fish.

Adsorption↗
PubMed2006

Hydration and contact ion pairing of Ca2+ with Cl- in supercritical aqueous solution.

X-ray absorption fine structure (XAFS) spectroscopy was used to measure the first-shell structure about Ca2+ in high-temperature aqueous solution. XAFS spectra were acquired at the Ca K edge at temperatures up to 400 degrees C and pressures up to 350 bars. For the system at 400 degrees C, both Ca (4038.5 eV) and Cl (2822.4 eV) K-edge data were acquired and a global model was used to fit the two independent sets of XAFS data. Measurements were made at the bending magnet beamline (sector 20) at the Advanced Photon Source, Argonne. Above 250 degrees C, a significant number of Ca2+-Cl- direct contact ion pairs form in agreement with existing thermodynamic data for this system. For a 1 m CaCl2 solution at 400 degrees C, the mean coordination structure about Ca2+ contains 3.2+/-0.6 water molecules at an average Ca-O distance of 2.356+/-0.026 A and 1.8+/-0.7 Cl- at a Ca-Cl distance of 2.677+/-0.007 A. An evaluation of the Ca and Cl preedge and near-edge (x-ray absorption structure) spectra provided further confirmation of the change in the Ca2+ first-shell structure and symmetry. Overall these measurements provide a structural basis for understanding solvation of Ca2+ in hydrothermal systems. These results also provide important new insights into the structural aspects of Ca2+ ion pairing that are the basis of many biological processes under ambient conditions.

Journal Article↗
PubMed2006

Delivery of telomerase reverse transcriptase small interfering RNA in complex with positively charged single-walled carbon nanotubes suppresses tumor growth.

PURPOSE: To determine whether -CONH-(CH(2))(6)-NH(3)(+)Cl(-) functionalized single-walled carbon nanotubes (SWNT) carrying complexed small interfering RNA (siRNA) can enter into tumor cells, wherein they release the siRNA to silence the targeted gene. EXPERIMENTAL DESIGN: -CONH-(CH(2))(6)-NH(3)(+)Cl(-) was used to mediate the conjugation of telomerase reverse transcriptase (TERT) siRNA to SWNTs. The ability of TERT siRNA delivered via SWNT complexes to silence the expression of TERT was assessed by their effects on the proliferation and growth of tumor cells both in vitro and in mouse models. RESULTS: The functionalized SWNTs -CONH-(CH(2))(6)-NH(3)(+)Cl(-) could facilitate the coupling of siRNAs that specifically target murine TERT expression to form the mTERT siRNA:SWNT+ complex. These functionalized SWNTs rapidly entered three cultured murine tumor cell lines, suppressed mTERT expression, and produced growth arrest. Injection of mTERT siRNA:SWNT+ complexes into s.c. Lewis lung tumors reduced tumor growth. Furthermore, human TERT siRNA:SWNT+ complexes also suppressed the growth of human HeLa cells both in vitro and when injected into tumors in nude mice. CONCLUSIONS: -CONH-(CH(2))(6)-NH(3)(+)Cl(-) functionalized SWNTs carry complexed siRNA into tumor cells, wherein they release the siRNA from the nanotube sidewalls to silence the targeted gene. The -CONH-(CH(2))(6)-NH(3)(+)Cl(-) functionalized SWNTs may represent a new class of molecular transporters applicable for siRNA therapeutics.

Animals↗
PubMed2006

Electromagnetic interference (EMI) shielding of single-walled carbon nanotube epoxy composites.

Single-walled carbon nanotube (SWNT)-polymer composites have been fabricated to evaluate the electromagnetic interference (EMI) shielding effectiveness (SE) of SWNTs. Our results indicate that SWNTs can be used as effective lightweight EMI shielding materials. Composites with greater than 20 dB shielding efficiency were obtained easily. EMI SE was tested in the frequency range of 10 MHz to 1.5 GHz, and the highest EMI shielding efficiency (SE) was obtained for 15 wt % SWNT, reaching 49 dB at 10 MHz and exhibiting 15-20 dB in the 500 MHz to 1.5 GHz range. The EMI SE was found to correlate with the dc conductivity, and this frequency range is found to be dominated by reflection. The effects of SWNT wall defects and aspect ratio on the EMI SE were also studied.

Artifacts↗
PubMed2006

Modeling of indoor air treatment of polychlorinated dibenzo-p-dioxins and dibenzofurans using high-efficiency particulate air-carbon filtration.

A high-efficiency particulate air (HEPA)-carbon filtration system was developed by the Access Business Group, LLC, to reduce the indoor levels of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). The HEPA filter removes the particle-bound PCDD/Fs, and the carbon filter removes the gaseous fraction. Because of the toxicity of PCDD/Fs, it is very difficult to handle them in the laboratory. In this study, mathematical modeling was performed to evaluate the performance of the HEPA-carbon filtration system for PCDD/Fs removal and to optimize its design and operation. The model was calibrated with experimental data conducted with toluene in a sealed room. Model simulations with four selected congeners demonstrated that it takes approximately 1 hr for the indoor air treatment system to reach the maximum removal efficiency and that the carbon air filter has a life time of 10(7) yr for dioxin removal. Given a zero emission from the HEPA filter, the overall removal efficiency is 78.7% for 2,3,7,8-tetrachloro dibenzo-p-dioxins, 89.8% for octa-chlorodibenzodioxin, 78% for tetra-chlorodibenzofuran, and 89.8% for octa-chlorodibenzofuran. The larger the mass emission from the HEPA filter, the lower the overall removal efficiency, and the larger the ratio of the filter flow rate (Q(f)) to the room flow rate (Q), the higher the overall removal efficiency. When the ratio of Q(f)/Q is 15, an overall removal efficiency of 90% can be reached for all four of the selected compounds. The removal of the four selected compounds does not change as the relative humidity increases < or = 90%.

Adsorption↗
PubMed2005

The structure of the homogeneous oxidation catalyst, Mn(II)(Br(-1))x, in supercritical water: an X-ray absorption fine-structure study.

Extended X-ray absorption fine structure (EXAFS) and X-ray absorption near edge structure (XANES) spectroscopies were used to probe the first-shell coordination structure about Mn(II) and Br(-1) ions that exist as contact ion pairs in supercritical water. This work was performed to clarify why solutions of MnBr2 in supercritical water are known to effectively catalyze the aerobic oxidative synthesis of terephthalic acid from p-xylene as well as a number of other methylaromatic compounds. The Mn and Br K-edge spectra were collected at the bending magnet beamline (sector 20) at the Advanced Photon Source, Argonne National Laboratory. The first-shell coordination structure about the Mn(II) ion changes from octahedral at ambient conditions to tetrahedral at supercritical conditions. Under supercritical conditions, the measured bond distances of Mn-OH2 and Mn-Br are 2.14 and 2.46 A, respectively. Direct contact ion pairs form with about 2 Br(-1) ions present in the first coordination shell of the Mn(II) ion. The structure of dissolved MnBr2, below 1.0 m, changes from essentially [Mn(II)(H2O)6]+2 to [Mn(II)(H2O)2(Br(-1))2] in supercritical water (scH2O). When an excess of Br(-1) ion is added, the bromide coordination number increases and the number of water molecules decreases. The results show that the initial MnBr2 catalyst in scH2O is tetrahedral with two Mn-Br contact ion pairs. The presence of the acetate anion deactivates the catalyst by formation of insoluble MnO.

Catalysis↗
PubMed2005

In situ XAFS and NMR study of rhodium-catalyzed dehydrogenation of dimethylamine borane.

In situ X-ray absorption fine structure spectroscopy (XAFS) and 11B NMR were used to study the rhodium-catalyzed dimerization reaction of dimethylaminoborane, (CH3)2NHBH3 or DMAB. XAFS spectra show that the active form of the rhodium catalyst is most likely composed of a six-atom Rh core surrounded by tightly bound external ligands. NMR results show the presence of monomeric dimethylamine borane (CH3)2NBH2, providing evidence that hydrogen formation from the homogeneous Rh species occurs by an intramolecular pathway. This is in contrast to thermal pathways that involve intermolecular B-N concurrent with hydrogen formation. This work shows that in situ XAFS spectroscopy offers a unique experimental tool to differentiate between heterogeneous and homogeneous catalysis.

Journal Article↗
PubMed2005

Preparation of a novel TiO2-based p-n junction nanotube photocatalyst.

TiO2 nanotube semiconductors contain free spaces in their interior that can be filled with active materials such as chemical compounds, enzymes, and noble metals, giving them a fundamental advantage over colloids. Although the unique shape of semiconductor nanotubes makes them promising for a range of potential applications, significant developmental research is required. In this research, a novel TiO2 nanotube photocatalyst was prepared that has a p-n junction. The photocatalyst particle surface is physically divided into reduction and oxidation surfaces, which poses a potential driving force for the transport of photogenerated charge carriers. The structure of this nanotube catalyst was characterized using a scanning electron microscope (SEM) and X-ray diffraction (XRD). The catalyst activity was evaluated by coating the catalyst on HEPA filters and determining the destruction rate of toluene in air. The p-n junction nanotube catalyst was shown to have a much higher photocatalytic destruction rate than that of commercially available, nonnanotube structured material, and a higher destruction rate for nanotube catalysts that did not contain a p-n junction.

Catalysis↗
PubMed2004

Magnetic powder MnO-Fe2O3 composite--a novel material for the removal of azo-dye from water.

Fine powder adsorbents or catalysts often show better adsorptive or catalytic properties, but they encounter the difficulties of separation and recovery in application. In this study, four inexpensive magnetic powder MnO-Fe2O3 composites used as adsorbent-catalyst materials were prepared and characterized. These materials could be recovered efficiently by a magnetic separation method. Their adsorptive properties for the removal of an azo-dye, acid red B (ARB), from water and the regeneration of adsorbents containing ARB by catalytic combustion was studied. These powder adsorbents showed excellent adsorption towards ARB under acidic conditions. A very fast adsorption rate was observed and could be well described by a pseudo-second-order kinetics model. The adsorption capacity increased with increasing Fe content and surface area of the adsorbent, and the highest adsorption capacity of 105.3 mg/g was obtained at pH 3.5. The adsorption was not affected by the presence of Cl-, but was significantly affected by SO4(2-). The adsorbent containing ARB can be regenerated by catalytic combustion of adsorbed ARB at 400 degrees C in air. Laboratory experiments demonstrated that this material is reusable.

Adsorption↗
PubMed2004

Synthesis and structure-activity relationships of 1-arylmethyl-5-aryl-6-methyluracils as potent gonadotropin-releasing hormone receptor antagonists.

Based on the SAR from bicyclic gonadotropin-releasing hormone (GnRH) antagonists such as 6-aminomethyl-7-aryl-pyrrolo[1,2-a]pyrimid-4-ones (5) and 2-aryl-3-aminomethyl-imidazolo[1,2-a]pyrimid-5-ones (6a,b), a series of novel uracil compounds (8) were derived as GnRH antagonists. The synthesis and SAR studies of 6-methyluracils as human GnRH receptor antagonists are discussed herein. Introduction of a small methyl substituent at the beta-position of the N3 side-chain improved the GnRH binding potency by 5-10-fold. Introduction of a methyl group of (R)-configuration at the alpha-carbon of the N-3 side-chain gave a modest improvement in binding affinity over the unsubstituted ethylene analogues. This modification enabled us to make uracil compounds without the labile 2-pyridylethyl motif on the basic nitrogen while still maintained excellent potency against the hGnRH receptor.

Animals↗
PubMed2003

Synthesis and structure-activity relationships of thieno[2,3-d]pyrimidine-2,4-dione derivatives as potent GnRH receptor antagonists.

The synthesis and SAR studies of thieno[2,3-d]pyrimidine-2,4-diones as human GnRH receptor antagonists to treat reproductive diseases are discussed. It was found that the 2-(2-pyridyl)ethyl group on the 5-aminomethyl functionality of the core structure was a key feature for good receptor binding activity. SAR study of the 6-(4-aminophenyl) group suggests that hydrophobic substituents were preferred. The best compound from this series had binding affinity (K(i)) of 0.4 nM to the human GnRH receptor.

Pyrimidinones↗
PubMed2003

Synthesis and photochromic properties of molecules containing [e]-annelated dihydropyrenes. Two and three way pi-switches based on the dimethyldihydropyrene-metacyclophanediene valence isomerization.

The syntheses of several new simple negative, a simple positive, and multiple negative photochromes containing the dihydropyrene-cyclophanediene photochromic system are described. The photo-openings of the negative photochromes, the [e]-annelated benzo (7), naphtho (9), anthro (11), furano (19), and triphenyleno (15) derivatives of the parent 2,7-di-tert-butyl-trans-10b,10c-dimethyl-dihydropyrene (5), as well as its 4,5-dibromo derivative (13), are described to give the corresponding cyclophanedienes, as well as their photoclosures and thermal closures back to the dihydropyrenes. These are compared to the results obtained for the positive photochrome dibenzo[e,l]dihydropyrene (21) and to the bis(dihydropyreno)chrysene (44) and the (dihydropyrenobenzo)(benzo)metacyclophanediene (47) photochromes, which have more than one photochromic switch present and thus have more than a simple "on-off" state. Thermodynamic data are obtained for the thermal closing reactions. The anthrodihydropyrene (12) has the fastest thermal closing (tau(1/2) = 20 min), while the furanodihydropyrene (19') has the slowest (tau(1/2) = 63 h) at 46 degrees C. An electrochemical readout of the state of the switch is demonstrated for the benzodihydropyrene (7).

Journal Article↗
PubMed2003

Effects of thyroxine on cardiac function and lymphocyte beta-adrenoceptors in patients with chronic congestive heart failure.

OBJECTIVE: To explore the effects of thyroid hormone (TH) on cardiac function and peripheral lymphocyte beta-adrenoceptors (beta-ARs) of patients with chronic congestive heart failure (CHF). METHODS: Twenty-eight patients with class III or IV advanced CHF due to dilated cardiomyopathy (DCM) or ischemic cardiomyopathy (ICM) were randomly divided into groups A and B. L-thyroxine (L-T(50)) was administered to group B. Exercise tolerance, chest X-rays, and echocardiographic parameters were obtained before and after one month of treatment, Ficoll-hypaque solution was used to separate peripheral lymphocytes, and (125)I-pindolol radioligand binding was used to measure beta-AR levels in peripheral lymphocytes. RESULTS: L-T(50) therapy improved cardiac output [CO, (2.98 +/- 0.31)L/min vs (3.24 +/- 0.28) L/min, P < 0.01], left ventricular ejection fraction (LVEF, 26.21% +/- 3.21% vs 37.93% +/- 9.01%, P < 0.01), and decreased isovolumetric relaxation time (IVRT, 0.12 +/- 0.04 vs 0.10 +/- 0.02, P < 0.01). Serum TH levels and the maximal number of beta-AR binding sites (beta(max)) in peripheral lymphocytes were lower in patients with CHF than in normal healthy people, but L-T(50) administration induced a beta-AR up-regulation on peripheral lymphocyte surfaces. L-T(50) was well tolerated without episodes of ischemia or arrhythmia. There was no significant change in heart rate or metabolic rate. CONCLUSION: TH administration improves cardiac function and beta-AR expression in peripheral lymphocytes of patients with CHF.

Adult↗
PubMed2002

The Molecule Pages database.

The Alliance for Cellular Signaling (AfCS)-Nature Molecule Pages will be a comprehensive database of key facts about more than 3,000 proteins involved in cell signalling. Each entry will be created by invited experts and be peer-reviewed. Alongside the large-scale experiments being conducted by the AfCS scientists, the wealth of information contained in this database offers the potential of accelerating the pace of discovery in signal transduction research.

Automation↗
PubMed2002

Expeditious syntheses of two carbohydrate-linked cisplatin analogs.

The syntheses of two carbohydrate-linked cisplatin analogs, namely lacto- and alpha-Gal-cisplatin, are described. A fusion enzymatic approach was used to create the diazido-alpha-Gal trisaccharide intermediate in the synthesis of alpha-Gal-cisplatin.

Carbohydrate Sequence↗