shawn Wei | Yunnan University (original) (raw)

Papers by shawn Wei

Molecular Endocrinology, 2002

Tumor suppressor p53 is known to inhibit transactivation by certain nuclear receptors, and overex... more Tumor suppressor p53 is known to inhibit transactivation by certain nuclear receptors, and overexpressed p53 is known to correlate with poor differentiation in liver cancer. Therefore, we investigated whether wild-type p53 might also affect the function of hepatocyte nuclear factor 4alpha1 (HNF4alpha1), an orphan receptor required for liver differentiation. Our results show that HNF4alpha1-mediated transactivation is repressed by p53 but that the mechanism of repression is not due to inhibition of HNF4alpha1 DNA binding. Rather, transfections with Gal4 fusion constructs indicate that the repression is via the ligand-binding domain of HNF4alpha1. Furthermore, we found that p53 in human embryonic kidney whole-cell extracts preferentially bound the ligand-binding domain of HNF4alpha1 and that the activation function 2 region was required for the binding. Competition for coactivator CREB binding protein could not entirely account for the repression but trichostatin A, an inhibitor of histone deacetylase activity, could reverse p53-mediated repression of HNF4alpha1. In contrast, p53-mediated repression of transcriptional activation of the same promoter by another transcriptional activator, CCAAT/enhancer-binding protein-alpha, could not be reversed by the addition of trichostatin A. These results suggest that p53, like other transcriptional repressors, inhibits transcription by multiple mechanisms, one of which involves interaction with the ligand-binding domain and recruitment of histone deacetylase activity.

Journal of Alloys and Compounds, 2011

a b s t r a c t N-doped TiO 2 nanotube arrays were prepared by electrochemical anode oxidation of... more a b s t r a c t N-doped TiO 2 nanotube arrays were prepared by electrochemical anode oxidation of Ti foil followed by treatment with N 2 -plasma and subsequent annealed under Ar atmosphere. The morphologies, composition and optical properties of N-doped TiO 2 nanotube arrays were characterized using field-emission scanning electron microscope (FE-SEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction spectrometer (XRD), Photoluminescence (PL) and UV-vis diffusion reflection spectroscopy (UV-vis DRS). Methylene blue (MB) solution was utilized as the degradation model to evaluate the photocatalytic activity of the samples under visible light irradiation. The results suggested N 2 -plasma treatment created doping of nitrogen onto the surface of photoelectrodes successfully and the N-doped TiO 2 nanotube arrays display a significantly enhancement of the photocatalytic activity comparing with the pure TiO 2 nanotube arrays under the visible light irradiation.

Biochemical and Biophysical Research Communications, 2008

TRPV5 and TRPV6 are two closely related epithelial calcium channels that mediate apical calcium e... more TRPV5 and TRPV6 are two closely related epithelial calcium channels that mediate apical calcium entry in the transcellular calcium transport pathway. TRPV5, but not TRPV6, is enhanced by protein kinase WNK4 when expressed in Xenopus laevis oocytes. We report that the majority of human TRPV5 exogenously expressed in the Xenopus oocyte plasma membrane was complexly Nglycosylated whereas that for human TRPV6 was core-glycosylated. Unglycosylated N358Q mutants of TRPV5 and TRPV6 were able to be expressed in the plasma membrane albeit with decreased abilities in mediating calcium uptake. Syntaxin 6, a SNARE protein in the trans-Golgi network, blocked the complex glycosylation of TRPV5 and TRPV6, rendered the channels in coreglycosylated form. Blocking complex glycosylation of TRPV5 either by syntaxin 6 or by N358Q mutation abolished the enhancing effect of WNK4 on TRPV5. Thus the difference in membrane expression of TRPV5 and TRPV6 explains the selective effect of WNK4 on TRPV5, which is likely on the secretory pathway involving complex glycosylation of channel proteins.

European Journal of Immunology, 2009

Chronic schistosome infection results in the suppression of host immune responses, allowing long-... more Chronic schistosome infection results in the suppression of host immune responses, allowing long-term schistosome survival and restricting pathology. Current theories suggest that Treg play an important role in this regulation. However, the mechanism of Treg induction during schistosome infection is still unknown. The aim of this study was to determine the mechanism behind the induction of CD4+CD25+ T cells by Schistosoma japonicum HSP60 (SjHSP60)-derived peptide SJMHE1 as well as to elucidate the cellular and molecular basis for the induction of CD4+CD25+ T cells during S. japonicum infection. Mice immunized with SJMHE1 or spleen and LN cells from naïve mice pretreated with SJMHE1 in vitro all displayed an increase in CD4+CD25+ T-cell populations. Release of IL-10 and TGF-β by SJMHE1 stimulation may contribute to suppression. Adoptively transferred SJMHE1-induced CD4+CD25+ T cells inhibited delayed-type hypersensitivity in BALB/c mice. Additionally, SJMHE1-treated APC were tolerogenic and induced CD4+ cells to differentiate into suppressive CD4+CD25+ Treg. Furthermore, our data support a role for TLR2 in SJMHE1-mediated CD4+CD25+ Treg induction. These findings provide the basis for a more complete understanding of the S. japonicum–host interactions that contribute to host homeostatic mechanisms, preventing an excessive immune response.

Genetics, 2005

The majority of Candida albicans strains in nature are a/␣ and must undergo homozygosis to a/a or... more The majority of Candida albicans strains in nature are a/␣ and must undergo homozygosis to a/a or ␣/␣ to mate. Here we have used a mouse model for systemic infection to test the hypothesis that a/␣ strains predominate in nature because they have a competitive advantage over a/a and ␣/␣ offspring in colonizing hosts. Single-strain injection experiments revealed that a/␣ strains were far more virulent than either their a/a or ␣/␣ offspring. When equal numbers of parent a/␣ and offspring a/a or ␣/␣ cells were co-injected, a/␣ always exhibited a competitive advantage at the time of extreme host morbidity or death. When equal numbers of an engineered a/a/␣2 strain and its isogenic a/a parent strain were coinjected, the a/a/␣2 strain exhibited a competitive advantage at the time of host morbidity or death, suggesting that the genotype of the mating-type (MTL) locus, not associated genes on chromosome 5, provides a competitive advantage. We therefore propose that heterozygosity at the MTL locus not only represses white-opaque switching and genes involved in the mating process, but also affects virulence, providing a competitive advantage to the a/␣ genotype that conserves the mating system of C. albicans in nature.

Through silicon vias (TSVs) are one of the major enabling technologies for three-dimensional pack... more Through silicon vias (TSVs) are one of the major enabling technologies for three-dimensional packaging (3DP). TSVs are usually plugged with plated copper for interconnection. However, the introduction of massive copper in the chip may cause device failure due to the fast diffusion of copper into silicon. In order to reduce this risk, a diffusion barrier layer should be deposited on the sidewall of TSVs between the plated copper and the bulk silicon. In addition, an insulation layer should be deposited as well to prevent short circuit. In this paper, the phenomenon of copper-to-silicon diffusion is characterized. The selected interfacial multilayer structure is Cu/Ti/SiO2. Although the ideal specimens should be TSVs with interfacial multilayer deposited on the side wall, it is rather difficult to perform surface analysis on a very small area. Therefore, planar analysis with interfacial multilayer deposited on the top surface of a silicon wafer is performed instead. For comparison purpose, additional cases without insulation layer and/or barrier layer are also investigated. A set of experiments is designed to study the effects of surface roughness and layer thickness. In addition, some samples are subject to high temperature storage for the study of thermal annealing effect.

Molecular & Cellular Proteomics, 2009

Lysine propionylation and butyrylation are protein modifications that were recently identified in... more Lysine propionylation and butyrylation are protein modifications that were recently identified in histones. The molecular components involved in the two protein modification pathways are unknown, hindering further functional studies. Here we report identification of the first three in vivo non-histone protein substrates of lysine propionylation in eukaryotic cells: p53, p300, and CREB-binding protein. We used mass spectrometry to map lysine propionylation sites within these three proteins. We also identified the first two in vivo eukaryotic lysine propionyltransferases, p300 and CREB-binding protein, and the first eukaryotic depropionylase, Sirt1. p300 was able to perform autopropionylation on lysine residues in cells.

This paper presents different design concepts and approaches of CMOS broadband amplifiers for opt... more This paper presents different design concepts and approaches of CMOS broadband amplifiers for optical communications and optical interconnects. The design techniques of distributed amplifier (DA), capacitive peaking, and inductor/transformer peaking are reviewed. Using the proposed inductive peaking techniques, we have demonstrated previously a 40-Gb/s transimpedance amplifier (TIA) in 0.18 μm CMOS and a broadband amplifier with a 70-GHz bandwidth in 0.13 μm CMOS. With an emphasis on low power and miniature characteristics, different TIA topologies are discussed for the emerging applications of optical interconnects. Our recent study demonstrates a TIA achieving a transimpedance gain of 54.5 dBΩ and a bandwidth of 4.3 GHz under power consumption of 11.5 mW with a chip area of only 0.0077 mm2 in 0.18 μm CMOS, which permits a data transmission rate up to 7 Gb/s for optical interconnect applications.

IEEE Microwave and Wireless Components Letters, 2012

An ultra-low-power 60 GHz low-noise amplifier (LNA) with a 12.5 dB peak gain and a 5.4 dB minimum... more An ultra-low-power 60 GHz low-noise amplifier (LNA) with a 12.5 dB peak gain and a 5.4 dB minimum NF is demonstrated in a 90 nm CMOS technology. The LNA is composed of four cascaded common-source stages with the gate-source transformer feedback applied to the input stage for simultaneous noise and input matching. Also, the drain-source transformer feedback is used in the following stages for gain enhancement and interstage/output matching. This LNA consumes only 4.4 mW from a 1 V supply with a compact core area of 0.047 .

Analytical Biochemistry, 2003

Mammalian liver disposes of acetaminophen and other ingested xenobiotics by forming soluble glucu... more Mammalian liver disposes of acetaminophen and other ingested xenobiotics by forming soluble glucuronides that are subsequently removed via renal filtration. When given in combination with the stable isotopes 2 H and 13 C, the glucuronide of acetaminophen isolated from urine provides a convenient ''chemical biopsy'' for evaluating intermediary metabolism in the liver. Here, we describe isolation and purification of urinary acetaminophen glucuronide and its conversion to monoacetone glucose (MAG). Subsequent 2 H and 13 C NMR analysis of MAG from normal volunteers after ingestion of 2 H 2 O and [U-13 C 3 ]propionate allowed a noninvasive profiling of hepatic gluconeogenic pathways. The method should find use in metabolic studies of infants and other populations where blood sampling is either limited or problematic.

Bioinformatics/computer Applications in The Biosciences, 2006

Motivation: To detect and select patterns of transcription factor binding sites (TFBSs) which dis... more Motivation: To detect and select patterns of transcription factor binding sites (TFBSs) which distinguish genes directly regulated by estrogen receptor-a (ERa), we developed an innovative mixture model-based discriminate analysis for identifying ordered TFBS pairs. Results: Biologically, our proposed new algorithm clearly suggests that TFBSs are not randomly distributed within ERa target promoters (P-value < 0.001). The up-regulated targets significantly (P-value < 0.01) possess TFBS pairs, (DBP, MYC), (DBP, MYC/MAX heterodimer), (DBP, USF2) and (DBP, MYOGENIN); and down-regulated ERa target genes significantly (P-value < 0.01) possess TFBS pairs, such as (DBP, c-ETS1-68), (DBP, USF2) and (DBP, MYOGENIN). Statistically, our proposed mixture model-based discriminate analysis can simultaneously perform TFBS pattern recognition, TFBS pattern selection, and target class prediction; such integrative power cannot be achieved by current methods.

Journal of Natural Gas Chemistry, 2011

Two Cu-Mo-Fe-O x samples, which can store and supply pure hydrogen through repeated redox reactio... more Two Cu-Mo-Fe-O x samples, which can store and supply pure hydrogen through repeated redox reaction (Fe 3 O 4 +4H 2 ↔3Fe+4H 2 O), were prepared by co-precipitation (FCM-C) and impregnation (FCM-I) methods, respectively, and the performance of hydrogen production from water were investigated. Compared with the impregnated sample, the co-precipitation sample presented better catalytic activity. The samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR) and temperature-programmed reduction (H 2 -TPR) techniques. XRD, FE-SEM and XPS results suggest that the FCM-C sample has smaller particle size and higher dispersion of iron oxide than that of FCM-I sample. In addition, FT-IR and H 2 -TPR analyses indicate that the weak interaction among metal oxides in FCM-C sample may induce facile reduction of active metal and superior property of hydrogen production by decomposing water in succession.

Journal of Chromatography B-analytical Technologies in The Biomedical and Life Sciences, 2007

Direct-injection LC-LC hybrid tandem MS methods have been developed for undertaking broad-based s... more Direct-injection LC-LC hybrid tandem MS methods have been developed for undertaking broad-based screening for acidic drugs in protein-precipitated plasma and neutral doping agents in equine urine. In both analyses, analytes present in the matrix were trapped using a HLB extraction column before being refocused and separated on a Chromolith RP-18e monolithic analytical column using a controlled differential gradient generated by proportional dilution of the first column&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s eluent with water. Each method has been optimised by the adoption of a mobile phase and gradient that was tailored to enhance ionisation in the MS source while maintaining good chromatographic behaviour for the majority of the target drugs. The analytical column eluent was fed into the heated nebulizer (HN) part of the Duospray interface attached to a 4000 QTRAP mass spectrometer. Information dependent acquisition (IDA) with dynamic background subtraction (DBS) was configured to trigger a sensitive enhanced product ion (EPI) scan when a multiple reaction monitoring (MRM) survey scan signal exceeded the defined criteria. Ninety-one percent of acidic drugs in protein-precipitated plasma and 80% of the neutral compounds in equine urine were detected when spiked at 10 ng/ml.

Applied Optics, 2009

The methodology of using mobile scanning lidar data for investigation of smoke plume rise and hig... more The methodology of using mobile scanning lidar data for investigation of smoke plume rise and highresolution smoke dispersion is considered. The methodology is based on the lidar-signal transformation proposed recently [Appl. Opt. 48, 2559]. In this study, similar methodology is used to create the atmospheric heterogeneity height indicator (HHI), which shows all heights at which the smoke plume heterogeneity was detected by a scanning lidar. The methodology is simple and robust. Subtraction of the initial lidar signal offset from the measured lidar signal is not required. HHI examples derived from lidar scans obtained with the U.S. Forest Service, Fire Sciences Laboratory mobile lidar in areas polluted by wildfires are presented, and the basic details of the methodology are discussed.

In this paper, we derive a necessary and sufficient condition for stability of networked control ... more In this paper, we derive a necessary and sufficient condition for stability of networked control systems (NCSs) in the mean square sense and introduce the packet dropping margin to determine the robustness of the system with respect to packet dropping. By analyzing the relationship between the packet dropping probability and stability robustness, it is shown that a controller designed by a robust pole assignment approach makes the system less sensitive to packet dropping.

Applied Physics Letters, 1995

We report a systematic study of the effective mass of two-dimensional (2D) holes in a series of t... more We report a systematic study of the effective mass of two-dimensional (2D) holes in a series of ten p-type GaAs/In0.20Ga0.80As/GaAs quantum well structure samples. The 2D hole density and its effective mass (m&amp;amp;ast;)are independently determined from Shubnikov–de Haas and cyclotron resonance measurements at 4.2 K. We find the m&amp;amp;ast; increases from (0.123±0.005) me to (0.191±0.015) me as the 2D hole