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Yong Chen

Publications and source records attributed to Yong Chen.

At least 37 records · Page 2Linked to original sources
PubMed2006

Nuclear and mitochondrial localization of the putative RNA helicase DHX32.

RNA helicases are involved in all aspects of RNA metabolism. We identified DHX32 as a novel gene with homology to the DHX family of RNA helicases. To gain insight into the role of DHX32 in RNA metabolism, we determined its subcellular localization. Electron microscopy immunocytochemistry detected DHX32 in the nucleus and mitochondria of the myeloid leukemia cell line HL-60. Confocal microscopy shows mitochondrial localization of DHX32 in HeLa cells. Double labeling showed close proximity of DHX32 to some of the newly synthesized RNA in the mitochondria. These results suggest that DHX32 is a putative RNA helicase that might be involved in regulating nuclear and mitochondrial gene expression.

Cell Nucleus↗
PubMed2006

Crystal structure of human histone lysine-specific demethylase 1 (LSD1).

Lysine-specific demethylase 1 (LSD1) was recently identified as the first histone demethylase that specifically demethylates monomethylated and dimethylated histone H3 at K4. It is a component of the CoREST and other corepressor complexes and plays an important role in silencing neuronal-specific genes in nonneuronal cells, but the molecular mechanisms of its action remain unclear. The 2.8-A-resolution crystal structure of the human LSD1 reveals that LSD1 defines a new subfamily of FAD-dependent oxidases. The active center of LSD1 is characterized by a remarkable 1,245-A3 substrate-binding cavity with a highly negative electrostatic potential. Although the protein core of LSD1 resembles other flavoenzymes, its enzymatic activity and functions require two additional structural modules: an N-terminal SWIRM domain important for protein stability and a large insertion in the catalytic domain indispensable both for the demethylase activity and the interaction with CoREST. These results provide a framework for further probing the catalytic mechanism and the functional roles of LSD1.

Catalytic Domain↗
PubMed2006

Molecular recognition thermodynamics of pyridine derivatives by sulfonatocalixarenes at different pH values.

The complex stability constants (Ka) and thermodynamic parameters (DeltaG degrees, DeltaH degrees, and TDeltaS degrees) for 1:1 complexation of water-soluble calix[4]arene, thiacalix[4]arene, and calix[5]arene sulfonates with pyridine and their methylated derivatives have been determined by means of isothermal titration calorimetry at pH 2.0 and 7.2 at 298.15 K, and their binding modes have been investigated by NMR spectroscopy. The results obtained show that sulfonatocalixarenes afford stronger binding ability toward pyridine guests at pH 2.0, attributable to the positive electrostatic interactions and the more extensive desolvation effects, but present higher molecular selectivity at pH 7.2 owing to the strengthened C-H...pi interactions. The pH-responsible binding ability and molecular selectivity are discussed from the viewpoint of electrostatic, pi-stacking, van der Waals interactions and size-fit relationship between host and guest. A close comparison further demonstrates that the C-H...pi interactions and van der Waals interactions play a more important role than pi...pi interactions in the present inclusion complexation.

Journal Article↗
PubMed2006

Adjustable fragmentation in laser desorption/ionization from laser-induced silicon microcolumn arrays.

Laser-induced silicon microcolumn arrays (LISMA) were developed as matrix-free substrates for soft laser desorption/ionization mass spectrometry (SLDI-MS). When low-resistivity silicon wafers were irradiated in air, sulfur hexafluoride, or water environment with multiple pulses from a 3 x omega mode-locked Nd:YAG laser, columnar structures were formed on the surface. The radii of curvature of the column tips varied with the processing environment, ranging from approximately 120 nm in water, to <1 mum in SF6, and to approximately 2 mum in air. In turn, these microcolumn arrays were used as matrix-free soft laser desorption substrates. In SLDI-MS experiments with a nitrogen laser, the microcolumn arrays obtained in water environment readily produced molecular ions for peptides and synthetic polymers at low laser fluence. These surfaces demonstrated the best ion yield among the three arrays. The threshold laser fluence and ion yield were comparable to those observed in matrix-assisted laser desorption/ionization. Low-femtomole sensitivity and approximately 6000 Da mass range were achieved. At elevated laser fluence, efficient in-source decay was observed and extensive peptide sequence information was extracted from the resulting mass spectra. The versatility of LISMA was attributed to confinement effects due to the submicrometer morphology and to the surface, thermal, and optical properties of processed silicon.

Silicon↗
PubMed2006

Ligands regulate cell surface level of the human kappa opioid receptor by activation-induced down-regulation and pharmacological chaperone-mediated enhancement: differential effects of nonpeptide and peptide agonists.

Two peptide agonists, eight nonpeptide agonists, and five nonpeptide antagonists were evaluated for their capacity to regulate FLAG (DYKDDDDK)-tagged human kappa opioid receptors (hKORs) stably expressed in Chinese hamster ovary cells after incubation for 4 h with a ligand at a concentration approximately 1000-fold of its EC(50) (agonist) or K(i) (antagonist) value. Dynorphins A and B decreased the fully glycosylated mature form (55-kDa) of FLAG-hKOR by 70%, whereas nonpeptide full agonists [2-(3,4-dichlorophenyl)-N-methyl-N-[(2R)-2-pyrrolidin-1-ylcyclohexyl-]acetamide (U50,488H), 17-cyclopropylmethyl-3,14-dihydroxy-4,5-epoxy-6-[N-methyl-trans-3-(3-furyl) acrylamido] morphinan hydrochloride (TRK-820), ethylketocyclazocine, bremazocine, asimadoline, and (RS)-[3-[1-[[(3,4-dichlorophenyl)acetyl]-methylamino]-2-(1-pyrrolidinyl)ethyl]phenoxy] acetic acid hydrochloride (ICI 204,448) caused 10-30% decreases. In contrast, pentazocine (partial agonist) and etorphine (full agonist) up-regulated by approximately 15 and 25%, respectively. The antagonists naloxone and norbinaltorphimine also significantly increased the 55-kDa receptor, whereas selective mu, delta, and D(1) receptor antagonists had no effect. Naloxone up-regulated the receptor concentration- and time-dependently and enhanced the receptor maturation extent, without affecting its turnover. Treatment with brefeldin A (BFA), which disrupts Golgi, resulted in generation of a 51-kDa form that resided intracellularly. Naloxone up-regulated the new species, indicating that its action site is in the endoplasmic reticulum as a pharmacological chaperone. After treatment with BFA, all nonpeptide agonists up-regulated the 51-kDa form, whereas dynorphins A and B did not, indicating that nonpeptide agonists act as pharmacological chaperones, but peptide agonists do not. BFA treatment enhanced down-regulation of the cell surface receptor induced by nonpeptide agonists, but not that by peptide agonists, and unmasked etorphine- and pentazocine-mediated receptor down-regulation. These results demonstrate that ligands have dual effects on receptor levels: enhancement by chaperone-like effects and agonist-promoted down-regulation, and the net effect reflects the algebraic sum of the two.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗
PubMed2006

Staged pendulous-prostatic anastomotic urethroplasty followed by reconstruction of the anterior urethra: an effective treatment for long-segment bulbar and membranous urethral stricture.

OBJECTIVES: To describe a novel surgical technique for male long-segment urethral stricture after pelvic trauma using the intact and pedicled pendulous urethra to replace the bulbar and membranous urethra, followed by reconstruction of the anterior urethra. METHODS: Two patients with long-segment post-traumatic bulbar and membranous urethral strictures with short left pendulous urethras who had undergone several failed previous surgeries were treated with staged pendulous-prostatic anastomotic urethroplasty followed by reconstruction of the anterior urethra. This procedure was divided into three stages. First-stage surgery was mobilization of the anterior urethra down to the coronary sulcus and then rerouted to the prostatic urethra followed by pendulous-prostatic anastomotic urethroplasty with transposition of the penis to the perineum. Second-stage surgery was transecting the anterior urethra at the revascularised coronary sulcus 6 mo later, followed by straightening of the penis and urethroperineostomy. Third-stage surgery was reconstruction of the anterior urethra 6 mo later. RESULTS: Postoperatively, the two patients reported satisfactory voiding. For patient 1, retrograde urethrography showed that the urethra was patent, and that the mean maximal flow rate (MFR) was 18.4 ml/s with no postvoiding residual urine after the third-stage surgery and at 3-yr follow-up. For patient 2, a 22F urethral catheter could pass smoothly through the urethra, and the MFR was 19.5 ml/s with no postvoiding residual urine at 2-yr follow-up. CONCLUSIONS: This procedure was an effective surgical option for men with complex long-segment post-traumatic bulbar and membranous urethral strictures, especially for those who had undergone failed previous surgical treatments.

Adult↗
PubMed2006

Method validation and determination of enantiomers and conformers in tofisopam drug substances and drug products by chiral high-performance liquid chromatography and kinetic and thermodynamic study of the interconversion of the conformers.

1-(3,4-Dimethoxyphenyl)-4-methyl-5-ethyl-7,8-dimethoxy-5H-2,3-benzodiazepine (tofisopam) contains one chiral center, so two enantiomeric forms exist. The ring system of tofisopam possesses two sterically stable boat structures, leading to two distinct conformers for each enantiomer. A method was developed for the separation of these enantiomers and conformers in the drug substances and drug products. Separation was achieved with a separation factor of at least 3.9 for any adjacent peaks. Validation of the method challenged linearity, limit of detection, limit of quantification, specificity, accuracy, repeatability, intermediate precision, robustness, and stability of standard and sample solutions, and all validation results met the acceptance criteria. A study of accuracy at 80%, 100%, and 120% levels gave recoveries of 100 +/- 1%. The RSD of six sample injections for repeatability was less than 0.5%. The detection limit of tofisopam enantiomer was as low as 0.12 microg/mL. The kinetics and thermodynamics of the interconversion of tofisopam conformers were also investigated, and the kinetic and equilibrium constants of the interconversion process were determined at 15 degrees C, 25 degrees C, and 35 degrees C.

Benzodiazepines↗
PubMed2006

Adenosine A(2b) receptor is highly expressed in human hepatocellular carcinoma.

High levels of adenosine accumulate in hypoxic tissues during the rapid growth of tumors, suggesting activation of adenosine receptors may facilitate tumor progress. The relevance of adenosine receptors to hepatocellular carcinoma (HCC), in particular the adenosine A(2b) receptor (A(2b)), is not yet fully understood. The aim of this study was to assess whether A(2b) was differentially expressed in normal and cancerous tissues and evaluate the clinicopathological correlation of A(2b) level in HCC. Expression of A(2b) in tumor cells was investigated by immunohistochemical staining. Protein analysis was done by Western blotting and evaluation of A(2b) mRNA expression levels utilized quantitative real-time PCR analysis of tissue samples of 64 hepatocellular carcinomas and in their paired adjacent normal tissues. Western blot data suggested that A(2b) was expressed predominantly in the cell membrane and cytoplasm of tumor cells and that the intensity of A(2b) protein expression was consistently higher in HCC than in adjacent normal tissues. Levels of A(2b) mRNA in HCC were significantly higher than in adjacent tissues, as measured by real-time PCR (P<0.001). With regard to venous invasion, satellite lesions and advanced pathologic Tumor-Node-Metastasis (pTNM) stage, the A(2b) level tended to be higher than that seen in negative cases (P<0.05). Our findings demonstrate that A(2b) expression is up-regulated in HCC, the expression level of A(2b) is correlated to tumor progression in HCC, and suggest that A(2b) may be a novel target for HCC therapeutic strategy.

Journal Article↗
PubMed2006

Miniaturization and automation of an internally cooled coated fiber device.

The internally cooled coated fiber device was miniaturized to allow its direct introduction into a gas chromatography injector, while maintaining a reasonable lifetime of the septum. The device was robust, and its fiber, which was accommodated in an 18-gauge needle, was reproducibly used for more than 100 injections without any coating failure. The fiber temperature was controlled within 5 degrees C of the preset value by use of a temperature controller, a solenoid valve, and stainless steel tubings with different inner diameter. The device was mounted and used on the CTC CombiPAL autosampler with minor modifications, such as enlarging the hole of the needle guide of the autosampler and coupling the temperature control system of the device to the autosampler through a logic circuit. The device was validated with the back equilibration of hydrocarbons preloaded in the fiber in air. The automation of the internally cooled coated fiber device provided the feasibility of high throughput for the analysis of analytes in complex matrixes that required simultaneous heating of the sample matrixes and cooling of the fiber coating.

Journal Article↗
PubMed2006

Internal energy transfer in laser desorption/ionization from silicon nanowires.

Laser-induced desorption/ionization from silicon nanowires (SiNW) is an emerging method for mass spectrometry of small to medium-size molecules. In this new technique, we examined the internal energy transfer to seven benzylpyridinium thermometer ions and extracted the corresponding internal energy distributions. To explore the effect of the energy-deposition rate on the internal energy transfer, two lasers with significantly different pulse lengths (4 ns vs 22 ps) were utilized as excitation sources. A comparison of ion yields indicated that the SiNW substrates required 5-8 times less laser fluence for ion production than either matrix-assisted laser desorption/ionization (MALDI) or desorption/ionization on silicon (DIOS). In contrast however, the survival yield (SY) values showed that the internal energy transferred to the thermometer ions was more than (ps laser) or comparable to (ns laser) MALDI but it was significantly less than in DIOS. The internal energy transfer was only slightly dependent on laser fluence and on wire density. These effects were rationalized in terms of the confinement of thermal energy in the nanowires and of unimpeded three-dimensional plume expansion. Unlike in MALDI from CHCA and in perfluorophenyl-derivatized DIOS, for desorption from SiNWs the effect of laser pulse length on the internal energy transfer was found to be negligible.

Energy Transfer↗
PubMed2006

Escherichia coli CorA periplasmic domain functions as a homotetramer to bind substrate.

CorA is a primary Mg2+ transporter in bacteria, which also mediates influx of Ni2+ and Co2+. Topological studies suggested that it could be divided into a large soluble periplasmic domain (PPD) and three membrane-spanning alpha-helixes. In the present study, glutathione S-transferase (GST) fusion Escherichia coli CorA PPD was purified by GST affinity chromatography, and PPD was obtained by on-column thrombin digestion. Size-exclusion chromatography indicated that purified PPD exists as a homotetramer. Single particle electron microscopy analysis of PPD and two-dimensional crystals of GST-PPD indicated that E. coli CorA PPD is a pyramid-like homotetramer with a central cavity. Comparison of the CD spectra of full-length CorA and PPD also suggested that PPD has similar secondary structure to the full-length CorA. Dissociation constants for CorA and PPD with their substrates, determined by dose-dependent fluorescence quench of ligands, suggested that purified PPD retains its substrate binding ability as native CorA. The CorA PPD structure described here may provide structural information for the E. coli CorA functional oligomeric state.

Cation Transport Proteins↗
PubMed2006

Drying of DNA droplets.

The evaporation kinetics of droplets containing DNA was studied, as a function of DNA concentration. Drops containing very low DNA concentrations dried by maintaining a constant base, whereas those with high concentration dried with a constant contact angle. To understand this phenomenon, the distribution of the DNA inside the droplet was measured using confocal microscopy. The results indicated that the DNA was condensed mostly on the surface of the droplets. In the case of high concentration droplets, it formed a shell, whereas isolated islands were found for droplets of low DNA concentrations. Rheologic results indicate the formation of a hydro gel in the low concentration drops, whereas phase separation between the self-assembled DNA structures and the water phase occurred at higher concentration.

Bacteriophage lambda↗
PubMed2006

Optical behaviors of conjugated-chain compounds containing benzene and furan units.

Thirteen conjugated-chain compounds which contain benzene and furan units were prepared, their optical behaviors, including UV-vis absorption coefficient (epsilon), absorption wavelengths (lambdaa), fluorescence emission wavelengths (lambdae), and quantum yields (Phi) were measured. Meanwhile, their LUMO and HOMO energy were determined by cyclic voltammetry and their second-order polarizations (betaxxx) values were determined by solvatochromic method, respectively. The results showed that this kind of compounds possess a shorter lambdaa (320-365 nm) and performance a higher Phi values, especially for 2aa, 2ab, 2ac and 2bb, their Phi values are all more than 90%. These compounds, except 2db, showed a higher betaxxx values in DMSO, especially for 2dc (75.77x10(-30) m5 C-1) and 2dd (83.32x10(-30) m5 C-1), than that 10-methyl-acridone (6.578x10(-30) m5 C-1) or 10-benzylacridone (6.845x10(-30) m5 C-1) in DMSO did, and second harmonic generation value of 10-methylacridone and 10-benzylacridone in powder are, respectively, 1.381 and 1.861 times of that value of urea. The betaxxx values and Phi values determined for these compounds in this work were lower than these values which were desired in the original work, this phenomena was explained from their molecular structures. This work confirmed that as these compounds performance shorter lambdaa and higher Phi values, they could be good blue-color optical materials for some fields, such as OLED materials, two-photo absorption materials, fluorescent dyes.

Benzene↗
PubMed2006

Secondary assembly of bile salts mediated by beta-cyclodextrin-terbium(III) complex.

A fluorescent cyclodextrin-Tb(III) complex is successfully synthesized and can include bile salts in its hydrophobic cavities. Therefore, it can efficiently induce the secondary assembly of small bile salt primary micelles to large micelle aggregates, and the aggregation process can be easily observed by transmission electron microscopy (TEM) and fluorescence microscopy.

Bile Acids and Salts↗
PubMed2006

Simultaneous photocatalytic reduction of Cr(VI) and oxidation of bisphenol A induced by Fe(III)-OH complexes in water.

Simultaneously photocatalytic reduction of Cr(VI) and oxidation of bisphenol A (BPA) in aqueous solution in the presence of Fe(III)-OH complexes were investigated under a 250 W metal halide lamp (lambda>or=365 nm). Synergy effect of the simultaneous photocatalytic oxidation and reduction of both pollutants was achieved. The effects of initial pH value, initial concentration of BPA, Cr(VI) and Fe(III) were preliminarily investigated. The results showed that both photocatalytic reduction of Cr(VI) and degradation of BPA could occur simultaneously in the Fe(III)/Cr(VI)/BPA ternary system, and the rates of photocatalytic reduction of Cr(VI) and the oxidation of BPA were more rapid at a low pH range of 2.0-3.0. The increase of the initial concentration of Fe(III) was favorable to both photocatalytic reduction of Cr(VI) and oxidation of BPA. The reduction efficiency of Cr(VI) decreased with increasing initial concentrations of Cr(VI) and BPA, but the degradation efficiency of BPA was not changed obviously at different Cr(VI) concentrations.

Benzhydryl Compounds↗
PubMed2006

Proteomic identification and functional characterization of a novel ARF6 GTPase-activating protein, ACAP4.

ARF6 GTPase is a conserved regulator of membrane trafficking and actin-based cytoskeleton dynamics at the leading edge of migrating cells. A key determinant of ARF6 function is the lifetime of the GTP-bound active state, which is orchestrated by GTPase-activating protein (GAP) and GTP-GDP exchanging factor. However, very little is known about the molecular mechanisms underlying ARF6-mediated cell migration. To systematically analyze proteins that regulate ARF6 activity during cell migration, we performed a proteomic analysis of proteins selectively bound to active ARF6 using mass spectrometry and identified a novel ARF6-specific GAP, ACAP4. ACAP4 encodes 903 amino acids and contains two coiled coils, one pleckstrin homology domain, one GAP motif, and two ankyrin repeats. Our biochemical characterization demonstrated that ACAP4 has a phosphatidylinositol 4,5-bisphosphate-dependent GAP activity specific for ARF6. The co-localization of ACAP4 with ARF6 occurred in ruffling membranes formed upon AIF(4) and epidermal growth factor stimulation. ACAP4 overexpression limited the recruitment of ARF6 to the membrane ruffles in the absence of epidermal growth factor stimulation. Expression of GTP hydrolysis-resistant ARF6(Q67L) resulted in accumulations of ACAP4 and ARF6 in the cytoplasmic membrane, suggesting that GTP hydrolysis is required for the ARF6-dependent membrane remodeling. Significantly the depletion of ACAP4 by small interfering RNA or inhibition of ARF6 GTP hydrolysis by overexpressing GAP-deficient ACAP4 suppressed ARF6-dependent cell migration in wound healing, demonstrating the importance of ACAP4 in cell migration. Thus, our study sheds new light on the biological function of ARF6-mediated cell migration.

ADP-Ribosylation Factor 6↗
PubMed2006

Experimental characterization of hydrodynamic dispersion in shallow microchannels.

Hydrodynamic dispersion in shallow microchannels with almost parabolic cross-sectional shapes and with heights much less than their widths is studied experimentally. Both long serpentine channels and rotary mixers are used. The experimental results demonstrate that the dispersion depends on the width rather than the height of the channel. The results are in quantitative agreement with a recently proposed theory of dispersion in shallow channels.

Journal Article↗